Vital Information about Engine Rebuilding, Buildups and Modifications

Why Aluminum Block Engines (except V-Twins) Don't Work Well for Pulling Competition -

An aluminum engine block will "bend and twist" a few thousands of an inch when hot and under pulling stress. Therefore, they'll lose valuable compression because the valves become unseated and the piston rings lose partial contact against the cylinder wall. Not to mention the main bearings are also put into a bind under the stress of pulling.

If the crankcase is building up too much air pressure in an OHV aluminum block engine, and blowing oil out the crankcase breather, the main cause of this the cylinder head(s) are warped and needs to be resurfaced on a large, flat sanding disc. New head gaskets needs to be installed, too. What happens is the metal in the heads between the pushrods (where there is no head bolt) become warped due to normal engine operating heat. New aluminum "bends and twists" a few thousands of an inch as the block and head(s) get hot for the first time. Crankcase oil plugs the gap as the piston travels downward on the intake stroke, and part of the compression goes into the crankcase upon the compression stroke. The engine will probably not blow oily smoke out the exhaust either. Once repaired, this shouldn't happen again.

Cast iron engine blocks on the other hand hold their shape a lot better when hot and under stress. Aluminum engines work best for conditions that doesn't place them in a lot of stress. Such as ATVs, racing go-karts, racing lawn mowers, etc. Because there's fresh air moving over the engine, keeping the metal cool, and the block isn't being strained by the vehicle pulling a heavy load. That's why cast iron Kohler engines work best for competitive pulling. Because cast iron is able to "hold its shape," handle high operating temperatures, severe stress, high compression and very high rpm (above 4,000 rpm). This is why riding mowers, lawn tractors, lawn and garden tractors all have aluminum block engines. And most garden tractors have a cast iron engine block.

In addition, on the cast iron block single cylinder Briggs and Stratton and Tecumseh engines, the valve stems are parallel to the cylinder. This means that the valve heads set further away from the piston. And in the cast iron block single cylinder Kohler engines, the valve heads set closer to the piston (valve stems and lifters are angled 4°). Therefore, the other engines can't build up as much compression as Kohler engines can. Plus, they can't flow as much air in and out of the combustion chamber at high rpm, like Kohler engines can.

To gain more power and torque from virtually any flathead two or twin cylinder engine, perform a professional valve job and the valve clearances will need to be increased. Resurface the cylinder heads on a flat sanding disc to insure proper head gasket sealing. Nothing else may be needed to be done to the engine, except for perhaps a professional tune up. Many twin cylinder engines have inadequate valve clearances and this robs the engine of proper operation and valuable power. Perform a professional valve job, and set the clearances (between the valve stems and lifters) at .010" for the intake and .014" for the exhaust. After increasing the valve clearances, the engine will start quicker, idle better and produce more power at low and high rpm.

To perform a professional valve job on a twin cylinder flathead B&S or Kohler engine, the parts that will be needed are: two head gaskets, two crankcase breather gaskets, intake manifold mounting gaskets and valve stem seals (for intake valves only). New valve guides, especially for the exhaust valves, may also be needed. But that's to be determined once the valves are removed. A quality-made valve spring compressor tool is required to remove and reinstall the valves. The valve faces and valve seats are to be reground or recut at 45° (intake valve faces for Kohler) 30° (intake valve faces for B&S & exhaust valve faces for Kohler) and 46° (intake seats for Kohler & exhaust seats for B&S) 31° (intake seats for B&S), respectively. If you can't do this yourself, a local automotive machine shop can do it for you. You'll need to take the engine or tractor to the shop to have the valve seats reground or recut. Make sure they're reground or recut at the proper angle, too! And it'll be a good idea to have both cylinder heads resurfaced on a flat sanding disc to ensure proper head gasket sealing. The head bolts can be reused. They rarely go bad. Top of page

Converting a vertical shaft twin cylinder flathead Briggs & Stratton engine into a horizontal shaft model -

The parts needed to convert a vertical shaft twin cylinder flathead B&S engine into a horizontal shaft model are as follows. The parts below must come off a horizontal shaft twin cylinder flathead B&S engine.

• Oil pan (to replace the side cover).
• Oil dipstick and tube.
• Side cover (to replace the oil sump cover).
• Intake manifold and carburetor.
• Install a steel oil dipper on each connecting rod.
• Drill oil holes in the block for the camshaft and crankshaft bearing surfaces so the oil will lubricate these vital moving parts.

Everything else on the engine should work with no modifications. The PTO end of the crankshaft will be a little long, being it's made for a vertical shaft engine. But it'll still work just fine in the horizontal position.

To install a twin cylinder engine into a Cub Cadet, on the narrow and wide frame Cubs, the frame rails will need to be cut down for installation of an opposed twin cylinder engine. But the spread frame Cubs are made for the opposed twin cylinder engine. And a V-twin engine will fit in virtually into any Cub Cadet with few modifications. The frame rails shouldn't have to be altered either. Go here for an example of a V-twin that was installed in a wide frame Cub Cadet: http://www.smallenginewarehouse.com/RepowerItems.asp?Brand=Cub%20Cadet&Model=1000.

When rebuilding an aluminum block engine, remember - as an aluminum block and cylinder head get hot for the first time, they "warp" or bend and twist a few thousands of an inch due to normal engine heat. This is called block (and related parts) warping. In other words, the metal "takes shape." It's normal for new engine parts and unavoidable. So be sure to have the cylinder head and other parts resurfaced on a flat sanding disc to insure 100% gasket sealing, and bore the cylinder to insure a 100% piston ring seal. After the parts get hot again, they will not bend and twist again. This is a one time deal.

How To Determine If An Engine Needs To Be Rebuilt -

First of all, Kohler engines can be rebuilt multiple times, as long as everything in it is rebuildable. If the cylinder is max'd out at .030" and worn, it can be sleeved back to STD size. And if the crank journal is worn, it can be reground undersize and a matching undersize connecting rod or one with bearing inserts installed. Or it can be "rounded up" and the rod resized to fit the perfectly round reground journal. There's lots of tricks that can be used to rebuild an engine. The engine should last a long time, too.

Before the engine is removed from the tractor and disassembled, first, remove the cylinder head and observe the top of the piston. If it's 100% coated with carbon, then the piston rings are in good condition. But if some of the carbon is washed away around the edges and there's oil present, this means that the rings are worn and the piston and rings need replacing, or maybe the cylinder needs to be rebored for installation of an oversized piston and rings assembly.

Now move to the valves. To test for leaking valves, with the cylinder head removed and the piston at TDC on the compression stroke (both valves fully closed), spray WD-40 or an equivalent light liquid around each valve and then use compressed air to blow through the exhaust and intake ports. Wrap a rag around the air nozzle and place it snug against the port so full air pressure will be against the valve. If bubbles form around the valves when applying the air pressure, this means that the valves are leaking and a professional valve job is required.

To remove the engine from a typical IH Cub Cadet, first disconnect the battery negative terminal and disconnect all the wiring from the engine and fuel line if the gas tank is separate from the engine. Then remove the PTO clutch engaging linkage, remove the engine mounting bolts, then slide the engine forward so it'll clear the clutch disc or driveshaft, then lift the engine out of the tractor.

Now remove the oil pan and connecting rod cap. Observe the rod cap for scoring or burning. Replace or repair it if necessary. Also, the crankshaft journal may be worn and if it is, it will need to be reground to the next undersize. And have the crank journal mic'd (precision measured with a micrometer) to determine if it's excessively worn. If it is worn, it can be reground to .010" and a .010" undersize connecting rod can be used or you can have your old rod bored for installation of .010" bearing inserts. But if it needs to be reground to .020" or .030", the rod will need to be bored for installation of matching bearing inserts. The only OEM rods available without a bearing are STD and .010" undersize.

The diameter of the Kohler crankshaft rod journals are as follows:

If the cylinder wall is badly scored or tapered, have it bored to the next oversize. The only pistons available for a stock engine are STD, .010", .020" and .030". If the cylinder is worn beyond for installation for a .030" piston/rings assembly, it will need to be sleeved for installation of a STD size piston/rings assembly. But if building an engine for more power, don't have the cylinder bored to a maximum of .030" if it doesn't need it. Because a .030" overbore won't necessarily give an engine more power. Having a longer crankshaft stroke increases the power.

And if you're wondering, the old model K141 (6¼hp) engine has a bore diameter of 2-7/8". The model K161 (7hp), which replaced the K141, has a bore of 2-15/16". It uses the same piston/rings assembly as the model K181 (8hp) engine. Pistons/rings assemblies are no longer available in the 2-7/8" size. When rebuilding a K141, the cylinder must be bored for use with a 2-15/16" piston/rings assembly, which will then make it a model K161. The connecting rod and crankshaft are the same in the K141 and K161, but is different in the K181.

Most of the time, cleaning the burnt aluminum from a crankshaft journal won't work because the journal itself may be scored or worn. Therefore, it'll be better to have it reground to the next undersize and install a matching undersize connecting rod. Or if an undersize rod or bearing inserts isn't available, have it reground undersize (to wherever it "cleans up") and resize the connecting rod for proper fit.

With engines when there's no an undersize connecting rod or bearing inserts available, if the crank journal is worn beyond STD and needs to be reground, it can be reground to where it is perfectly round again, and then the connecting rod can be resized so it'll fit the smaller diameter undersize journal.

To fit the rod to a smaller crank journal...

1. First, the worn crank journal is reground until it's perfectly round again, despite if it's .006", .008" or whatever.
2. Then a few thousands of metal is removed from the mating end of the rod cap.
3. Fasten the cap to the rod. The big hole in the rod is now oblong or "egg shaped."
4. Resize the hole until it's .002" larger than the diameter of the crank journal. This reshapes the hole into a perfect circle again, only smaller in diameter. This can only be performed on a rod with a good bearing surface. It cannot be done on a burnt or heavily scored connecting rod.
5. This works very well and it lasts as long as an ordinary STD rod and crank journal. Click here if you're interested in having this service performed.

Don't Be A Slob When Rebuilding An Engine!

Always be professional whenever you rebuild an engine! Before assembling a fresh engine, always take the time to provide a neat and absolutely clean work environment. Make sure that your repair table or bench is sturdy enough to support the weight of a fully assembled cast iron bock Kohler engine. And make sure that your tools, shop/business towels, engine parts and hands are clean, too. Don't allow any dust or dirt to enter the work area, including the engine block and it's internal parts. If necessary, place the engine parts on a large, clean cloth or cardboard to help keep them clean and organized until they're ready to be installed. The reason everything should be kept as clean as possible is because even the smallest bit of dirt inside an engine will "grind away" at the internal parts when the engine is in operation, causing unnecessary and expensive wear.

You can also use an automotive engine stand to rebuild a Kohler engine. Just use the two starter bolt holes on the side of the block to mount your engine to the stand. You can completely disassemble and reassemble the entire engine, except for the starter, and you can get at everything on the outside and inside of the engine with no problems.

To "basically" overhaul or rebuild an engine that burns a lot of oil, all that needs to be done on a Kohler engine is remove the oil pan and cylinder head, disconnect the connecting rod from the crankshaft and then drive the piston and rod out of the block with a long wooden stick and a medium size hammer. Inspect the entire piston and cylinder wall for wear. If no wear is evident, then install a new set of rings on the piston (thoroughly clean the parts first though) and reinstall the piston in the block as described. But to do a professional and complete rebuild, read the rest of the information in this web page and linked pages.

Information About Using Imported/Aftermarket Engine Parts -

Most imported pistons, rings, rods and other parts from Rotary or Stens hold up VERY WELL. We've used these parts in our own equipment and pulling tractors for many years and we've sold them to our customers with no complaints whatsoever. Besides, it's how well the engine block and crankshaft are machined (cylinder bored straight, crank journal reground to OEM specs, cleanliness of the parts and work area, etc.), that determines how well and how long internal engine parts will hold up. Don't blame shoddy workmanship on shoddy parts.

Important Information About Kohler Crankshafts -

Crankshafts, rather being made of steel or cast iron, and despite how well-balanced the rotating parts are in a pulling engine, suffer a lot of vibration at very high rpm in a single cylinder engine. Therefore, if possible, before purchasing a used crankshaft, it's best to look it over for hairline cracks with a strong magnifying glass or better yet, a powerful microscope. And as the saying goes about buying anything off of eBay: BUYER BEWARE! So ask for a money-back guarantee, or you may have nothing but a piece of scrap metal on your hands.

Identifying Kohler Crankshafts -

• To identify the 10, 12, 14 and 16hp Kohler crankshafts, the 10hp cranks have a shorter stroke than the other cranks. You can compare a 10hp crank to a 12, 14 or 16hp crank by placing them side by side, and with the counter weights down, looking at the bottom part of the rod journal, the journal on the 10hp will be closer to the main journals. (3/8" of difference in stroke.)
• The 12hp crankshaft is different from the 14 and 16hp cranks because the counter weights are machined off for the lighter-weight 12hp piston assembly. NOTE: Some 10hp cranks also have the counter weights machined off like the 12hp does, but some don't.
• And the 14hp and 16hp cranks are identical in weight and appearance. Some may have a few more holes drilled into the counter weights, but that's the only difference.

How to Remove Only the Crankshaft from a Kohler Engine -

1. Remove the flywheel and anything that's on the PTO end of the crankshaft.
2. Remove the cylinder head.
3. Remove the oil pan.
4. Remove the piston/connecting rod assembly from the engine block.
5. Remove the bearing plate.
6. Finally, being very gentle, bump the PTO end of the crankshaft with a large brass head hammer or a large hammer and wooden block to remove it from the engine block.
7. And if an engine originally came with balance gears, there's no need to reinstall them. They serve very little purpose and they may break, possibly destroying the engine block.

Here's Something Important To Keep In Mind About A Reground Crankshaft Journal -

Sometimes as the rod journal (crank pin) wears, it will develop a "flat spot" at a certain place when the piston is at the ATDC position on the compression stroke. The combustion process places the most pressure on the piston and connecting rod at this particular point, which squeezes the oil out between the rod bearing surface and crank journal, causing brief metal to metal contact. As this happens, this point wears more than the rest of the journal, causing the journal to become oval or "egg shaped." Sometimes the upper part of the connecting rod will wear as well, but in most cases, it's the part that moves the most that wears more, which is the crank journal.

When regrinding a journal, and if a standard size journal is not worn past .005" on the low side or the "flat spot," then the crank grinder person can regrind it "centered" to the next undersize, which is .010", or if he gives it an extra .001" of additional oil clearance, it'll have a .011" undersize journal and the crankshaft will retain it's original stroke. But if a standard size journal is worn .006" or more, then the crank grinder can "cheat" and regrind the journal to the next undersize by offsetting the journal .006" or more in the lathe and regrind it to .010". By doing this, and depending on the amount of wear the journal had and the location of the low side or "flat spot," the crankshaft will have a slightly longer or shorter stroke. Otherwise, if the severely worn journal were to be reground "centered," it would have to go to .020" undersize, and the stock stroke will be retained. The decrease or increase of the stroke on a crankshaft with a worn STD, .010" or .020" journal can vary from .001" to .005". and as much as .010" on a STD journal that's been reground to .020" undersize or even .015" on a STD journal that's been reground to .030" undersize! So when a pulling club's rules state that an engine must have the stock factory length stroke, and if a crankshaft was reground, it may actually have a slightly longer or shorter stroke.

FYI - Oil clearance is the distance between the connecting rod bearing surface and crank journal. A thin coat of oil is supposed to keep all moving parts inside an engine from making contact with each other. If there's too little oil clearance between the rod and crank, especially in a high rpm engine, the rod will swell due to excessive heat, and then the rod will make contact with the crank and burn on the journal. If there's too much clearance, the rod will knock and possibly break at higher rpm, which could destroy the entire engine block.

When having a crank journal reground for an undersize bearing, it'll be a good idea to indicate to the crank grinder person that you want it ground for high-performance use by writing (with a bright-colored paint marker) the word RACE on one of the counterweights. The grinder person will then give the journal an additional .001" of oil clearance to prevent overheating both the bearing and journal. By the way - the extra .001" of clearance will not cause the rod to make a knocking sound.

More Information About the Crankshaft Journal -

The heat-treating or hardening process that Kohler uses on the rod journal area obviously goes deep into the crank. Because it's been proven that when the journal is ground for an undersize bearing, a .010", .020" or even a .030" undersize bearing can be used with no problem. Myself and many other pullers use undersize bearings in our pulling tractors, and I have no problems with the crank journal wearing. Heck, I've been using a .020" undersize bearing with the same crankshaft in our 30 c.i. tractor for 5 years and in about 75 pulls, and the crank journal hasn't worn at all. Most crank journals wear because of dirty motor oil or the wrong viscosity of oil is used. Not because of "soft metal" in the journal. Actually, the bearing material is not supposed to make contact with the crank journal. They're supposed to be kept separate by clean motor oil. And as far as cast iron Kohler crankshafts breaking is concerned, an undersize journal shouldn't make a cast crank break. I've always seen them break next to the journal, not in the journal area. As with anything, crankshafts break because something makes them break. Either out-of-balance parts, dirty flywheel taper/crankshaft taper or a manufacturing defect makes a crankshaft break.

By the way, a crank journal that's been turned .030" undersize will help to produce slightly more rpm and horsepower because there's less bearing surface to cause friction. Some NASCAR engineers do this to their racing engines. It works.

If you have a crankshaft that's made for a special purpose, and it has a worn .030" journal, and that particular crankshaft is no longer available, well, the journal can be welded up and reground back to STD size. Here's one place who can do this for you: Big 2 Engine Rebuilders, Inc., 3214 25th Ave., Gulfport, MS 39501-5909 Phone: 228-863-5425 FAX: 228-868-8728. Ask for Pete Bloss.

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If you need any of the services performed or items listed below, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA | Phone: 1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. More of our parts & services: Engine Rebuild Parts, Machine Shop Services, Engine Rebuilds & Build-up and Exhaust Header Pipe Kits
Crankshaft Repairs - Remove burnt aluminum and polish journal to shiny finish: $10.00 each journal. I chuck the crankshaft in my big metal lathe, turn it on slow and use my crankshaft polisher with a sanding belt to remove the burnt aluminum. This works great until the aluminum is gone, but sometimes the journal is scored or worn. Then it requires regrinding to the next undersize. If it's not scored or worn, then it can be reused as is. But if it is worn, an undersize rod and possibly one with a bearing insert is required. If it does need regrinding, then there's no charge for cleaning it. Regrind journal (crank pin): $50.00 per journal, plus return shipping & handling. Note: Kohler crankshafts can be reground to .030" undersize and still be safe to use with matching undersized bearing inserts installed in the connecting rod. And all crankshafts, rather if they're automotive or small engine, are checked for straightness before grinding. If they're bent or twisted, sometimes they can be straightened. I also do offset crankshaft grinding to increase the length of the stroke at no extra charge. With engines when there's no an undersize connecting rod or bearing inserts available, if the crank journal is worn beyond STD and needs to be reground, it can be reground to wherever it "cleans up" or is true again, and then the connecting rod can be resized so it'll fit the smaller undersize journal. To fit the rod to the smaller diameter crank journal, metal is removed from the mating end of the rod cap, then the cap is fastened to the rod. The big hole in the rod is now oblong or "egg shaped." Then the hole is resized until it's .002" larger than the diameter of the crank journal. This reshapes the hole into a perfect circle again, only smaller in diameter. This can only be performed on a rod with a good bearing surface. It cannot be done on a burnt or heavily scored connecting rod. This works very well and it lasts as long as an ordinary STD rod and crank journal.The cost for doing this is $75.00 labor, plus return shipping & handling. If you're interested, I will need your crankshaft and connecting rod. Repair broken off 5/8" stud on flywheel end of crankshaft. Center drill and cut threads for a 3/8" diameter grade 8 bolt in the end of crankshaft. $25.00 labor, plus return shipping & handling. Drill hole and cut 7/16-20 NF threads in the PTO end of the crankshaft for bolt and flat washer. $25.00.
Used OEM Crankshafts - 10hp, 12hp, 14hp and 16hp K-series and Magnum flathead single cylinder engine crankshafts. These cast iron cranks are a genuine Kohler part, they're used, but in good condition. These were in stock engines that never exceeded 3,600 rpm for a long period of time. They may have either a 1" or 1-1/8" diameter x 3-1/2" long keyed PTO shaft and may have a STD or freshly reground .010", .020" or .030" undersized journal. Although .030" is rare, it's still safe to use. [When available.] 10hp (K241/M10) $100.00 each, plus shipping & handling. 12hp (K301/M12) $150.00 each, plus shipping & handling. 14hp (K321/M14), 16hp (K341/M16) and 18hp (K361) $125.00 each, plus shipping & handling. NOTE: I need to know the dimensions of the PTO shaft on your crankshaft so I can match it to one that I may have in stock. Measure the diameter and length from the gear teeth.
New main crankshaft bearings for 7hp and 8hp Kohler K-series and Magnum single cylinder cast iron flathead engines. These are specifically designed to provide maximum performance by means of precise ball implement selection. Heat treated. Good for high performance use. Made in China, but has the same quality as OEM Kohler bearings for long wear. Dimensions: 1.18" i.d. x 2.44" o.d. x .62" width. $15.00 each, plus shipping & handling. Part # 150-960 New 8 ball main crankshaft bearings for 10hp, 12hp, 14hp, 16hp (flatheads) and 18hp (OHV) Kohler K-series and Magnum single cylinder cast iron engines. These are specifically designed to provide maximum performance through precise ball implement selection. At higher rpms, bigger balls run cooler which create less rolling resistance than bearings with smaller balls. Heat treated. Good for high performance use. Made in China, but has the same quality as OEM Kohler bearings for long wear. Replaces Kohler part # 235376. Dimensions: 1.57" i.d. x 3.54" o.d. x .90" width. $20.00 each, plus shipping & handling. Part #150-973 NOTE: With the main bearings removed from an engine, and if all the oil is cleaned from the bearings, allowed to thoroughly dry, and then the bearings are spun by hand, and if the bearings isn't worn much or at all, they might feel "rough" and make a rattling sound. This rattling sound isn't necessarily because the bearing is worn. The noise is caused by the balls running dry on the races because there's no oil to separate them. They're simply making metal to metal contact. Try applying a small amount of motor oil to the balls/races and then spin them. They should now be a lot quieter. The same thing will happen with new ball bearings. By the way - Most main bearings in a Kohler engine will wear extremely little, if any at all, and usually don't require replacing. Although some main bearings will wear (which is obvious), and need to be replaced. And excessively worn main bearings will make a rumbling noise and the engine will have a more than-usual-vibration.
Magnetic drain plug. Has 3/8" square head with 3/8" NPT threads. Universal fit. Helps trap metallic pieces inside crankcase to reduce engine wear. $3.50 each, plus shipping & handling.
Oil Drain Valve. Has 3/8" NPT threads (5/8" diameter). Universal fit. Easy to use! NOTE: Valve T handle has left-hand threads. $7.00 each, plus shipping & handling. Other sizes also available.
Self-tightening flywheel retaining jam nuts for threaded stud on end of K-series and steel crankshaft. Guaranteed to stay tight! Torque each at 65 ft. lbs. IMPORTANT: Apply thin coat of oil on threads of crankshaft before installing nut. 5/8" diameter, fine thread (5/8-18 NF). $1.50 each, plus shipping & handling. 3/4" diameter, fine thread (3/4-16 NF). $1.75 each, plus shipping & handling.		Flywheel retaining bolts for threaded hole in end of crankshaft. 1-1/2" long (when measured under head). Each bolt comes with split lockwasher. IMPORTANT: Apply thin coat of oil on threads before installing. 3/8" diameter, fine thread, grade 8 (3/8-24 NF; torque at 35 ft.lbs.). $1.00 each, plus shipping & handling. 5/8" diameter, fine thread, grade 5 (5/8-18 NF; torque at 65 ft.lbs.). $1.50 each, plus shipping & handling.
	Extra Thick Steel Washers for retaining flywheel and/or Cub Cadet aluminum clutch adapter hub to flywheel. A must to prevent hub breakage! Available in 3/8", 5/8" or 3/4" diameter center hole x 1-1/4" o.d. x approximately 1/4" thick. $3.00 each, plus shipping & handling. (The 3/8" washer is the same used for the solid motor mount kit.)	Steel Adapter Step-Washer for mounting Cub Cadet aluminum clutch hub with 5/8" center hole to Kohler Magnum crankshaft with a 3/8" bolt. A must to center hub and prevent hub breakage! $8.00 each, plus shipping & handling.

If a stock engine runs with a "hunting" sound, and the governor lever moves side to side while running at around 3,600 or 4,000 rpms, and if adjusting the carburetor or adjusting the rpms doesn't fix the problem, then perhaps the governor gear/flyweights assembly is worn on its stub shaft, or the shaft itself is worn. This will cause the governor gear to wobble around on its shaft, which will cause the governor to oscillate. And the engine will run erratic. To fix this problem, the governor gear and shaft must be replaced with new ones, or a cast iron governor gear. (Plastic governor gears are known to wear more often than cast iron ones.)

How to Remove and Replace the Governor Gear/Flyweights Assembly in a Single Cylinder Kohler Engine -

1. Remove the internal parts of the engine (mainly the crankshaft and camshaft).
2. Remove the governor gear retaining screw (the Phillips head screw that's on the outside of the block).
3. The governor gear can now slide off the stub shaft.
4. If the engine is going to be rebuilt and the block thoroughly cleaned, be sure to remove and save the small thrust washer that's on the governor gear's stub shaft! This special washer is made of either hardened steel or bronze for durability. A lot of people are not aware of this washer and it usually falls out of the block and gets lost while cleaning inside the block.
5. Install the new governor gear assembly in reverse order of removal.

Plastic VS Cast Iron Governor Gear Assemblies -

The most popular Kohler governor gear assembly nowadays for competitive stock garden tractor pulling are the ones that's made of cast iron. These are no longer made or available from Kohler or any other source. They were used in the 4hp, 6¼, 7hp, early 8hp, early 10hp and 12hp K-series Kohler engines 'til the late 1960s. It's impossible to tell if an engine has a metal governor gear by looking at it from the outside. The only way of knowing for sure is remove the oil pan and look at it from inside. There's really nothing special about the cast iron governor gear, except when the governor linkage is disconnected, they can withstand very high rpms and won't explode (break apart) like the plastic governor gears sometimes do. The reason the cast iron ones are so popular nowadays among stock pullers is because some pullers like to compete in two separate classes, one class that has an engine rpm limit of around 4,000± and another class with a higher rpm limit, or open rpm. Consider this: The governor gear spins 1.25 times faster than the crankshaft. This means at 4,000 rpm, the governor gear spins at 5,000 rpm. At 6,500 rpms, it spins at 8,125 rpms! And when using a plastic governor gear, don't worry, as long as the governor linkage is adjusted correctly, it should hold up just fine in an engine that will never operate above 4,000 rpm. The cast iron governor gear will fit all Kohler K-series and Magnum 4hp-16hp flatheads, 18hp K361 OHV single cylinder cast iron block and the KT-series and Magnum flathead twin cylinder engines.

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If you need a governor gear assembly or new stub shaft, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA | Phone: 1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. More of our parts & services: Engine Rebuild Parts, Machine Shop Services, Engine Rebuilds & Build-up and Exhaust Header Pipe Kits Used, but in good condition, governor gear assemblies for Kohler K-series and Magnum 10hp-16hp flatheads, 18hp K361 OHV single cylinder cast iron block engines, and KT-series flathead twin cylinder engines.
Plastic Governor Gear. Good for up to 4,000 rpm. OEM Kohler part # A-235743-S. Used, but in excellent condition: $15.00 each. [When available.] New: $36.00 each. Plus shipping & handling.	Cast Iron Governor Gear. Good for above 4,000 rpm. No longer available from Kohler. Used, but in excellent condition. $40.00 each, plus shipping & handling. [When available.]	New 3/8" diameter stub shaft for governor gear. Precision ground, heat-treated alloy steel. Replaces Kohler part # 235125-S. $3.00 each, plus shipping & handling.	New Bronze Thrust Washer for Governor Gear. Replaces Kohler # 237022-S. $3.00 each, plus shipping & handling.

All K-series cast iron block single cylinder Kohler engines come with what is called a throttle stop. It's a piece of angled steel that's fastened under the lever where the governor spring and throttle cable is attached. If an engine doesn't have one, fabricate it out of 1/8" x 1/2" x 2" flat steel. Drill a 1/4" hole 1/2" from one end, and bend it in the middle 90 degrees, and then install it under the lever. To limit an engine's rpm of an engine, either adjust the throttle stop so the lever bumps against it, set the governor spring ends in different holes on the [long] governor lever, adjust the throttle cable housing or the linkage.

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If you need a Precision Handheld Tachometer, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA | Phone: 1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. To accurately determine the rpm of an air-cooled small gas engine is by using a quality wireless tachometer, such as the handheld tach by Dixson. This is a precision handheld solid state wireless tachometer with an analog reading. The antenna is held near the spark plug wire and it gives a correct reading rpm for all 2 and 4 cycle single and twin cylinder engines with magneto or battery ignition. Note: Divide the reading by half on an engines with camshaft operated ignition points. Reads 0 to 15,000 rpm in two scales. Works perfect when performing a tune-up, setting the rpm on all stock pulling tractors when rules require a limited rpm, and testing the rpm on high-performance engines. Uses one 9 volt battery, which is included with purchase. Manufactured by Dixson. $100.00 each, plus shipping to your zip code. More of our parts & services: Engine Rebuild Parts, Machine Shop Services, Engine Rebuilds & Build-up and Exhaust Header Pipe Kits

NEVER USE GASOLINE OR A HIGHLY FLAMMABLE LIQUID TO CLEAN YOUR PARTS! Gas cleans good, but it's extremely flammable, making it too dangerous to handle. The best (and safest) way to clean an engine block and its parts for rebuilding is to wash all parts with cleaning solvent (or mineral spirits, also known as paint thinner). Personally, we've always used paint thinner to clean our engine parts.

A product that works great for cleaning engine parts is Greased Lightning^® Multipurpose. But use caution when using this product! It will remove the paint. So it's best to use it on bare metal or parts that need repainting.

For stubborn or caked-on grime, use a heavy duty oven spray cleaner, such as EASY-OFF® Heavy Duty Oven Cleaner or EASY-OFF^® Fume Free Max Oven Cleaner. (Use the fume-free one so you can breath.) Just spray the parts thoroughly, let set a few hours or overnight, then blast the grime and debris off with a high pressure (water) washer. Pressure from an ordinary garden hose just won't cut it. After cleaning, blow dry the parts and be sure to coat the bare metal with oil so they won't rust. If oven cleaner won't work, take the cast iron and steel parts to an automotive machine shop and have them "hot tanked" and have the aluminum parts sandblasted. I don't suggest sandblasting cast iron engine blocks or related parts because some of the sand can become lodged inside the engine and come loose when the engine is in operation, causing severe internal engine wear. Personally, I just coat the parts with oven cleaner and then blast the dirt off with our 1,000 psi water pressure washer.

How to Get More Power Out of a Stock Engine -

It takes three things to make an internal combustion engine run: compression, carburetion and ignition. There's three things that make an internal combustion engine run: Carburetion, compression and ignition. Fuel needs to get to the carburetor and then into the engine. The engine needs to have adequate compression to fully compress the air/fuel mixture to make power. And the ignition needs to be strong enough to ignite the air/fuel mixture. The ignition timing must also need to be set correctly to ignite the air/fuel mixture precisely at 20° BTDC to take full advantage of the exploding gases. Actually, it takes four things to make an engine run, including the starting system. If an engine won't start or if it's hard to start, and it has adequate compression, the carburetor and ignition seems to be working fine, then the only thing left is the starting system. Perhaps the starter motor or battery is going bad. They probably appear to be operating normal, but maybe one or the other isn't cranking the engine over fast enough to produce adequate compression to start the engine. I've seen this happen a few times. But if the compression, carburetion or ignition is weak or defective, power will be decreased dramatically. When checking for loss of power, always check the following things:
ü Carburetion is when an adequate amount of fuel and air mixture enters an engine smoothly.
ü Check the ignition timing. If the timing is retarded or over advanced, the engine will lose power and run sluggish. Check for a worn points lobe on the camshaft, too.
ü Compression is when the air/fuel mixture is adequately pressurized in the combustion chamber on the compression stroke. The secret to gaining more horsepower and torque is increase the compression ratio and improve the air flow in and out of the combustion chamber.
ü Another way to gain more power from the high rpm is to install a special camshaft along with larger diameter valves, stiffer valve springs and porting/polishing the intake and exhaust runners.
ü Apply epoxy (such a J-B Weld) inside the intake port and smooth it so the air will flow without any restrictions into the combustion chamber. This works great. But before applying the epoxy, make sure the port is absolutely clean or the epoxy won't bond to the engine block.
ü and a few other things that's mentioned elsewhere in our pulling tips web pages.

FYI - When everything that's mentioned here is performed to an engine, it should produce maximum power. But if just a few things are performed, the power will be increased, but not to the maximum. For example: if the valves are reworked for more airflow, then the intake and exhaust runners would also need to be enlarged, and the carburetor would need to be bored to take full advantage of the maximum airflow. But if the intake runner isn't enlarged, this would create a "bottle neck," and air will be restricted. The same goes for the valves and carburetor. Also, if a cam with more duration is installed, then the valve and air intake system would need to be maximized to take full advantage of the performance camshaft. But if just the cylinder head is milled, and nothing else is done to the engine, this alone should add a few ponies to an engine. The same goes when just popping the piston out of the cylinder. Each time a performance thing is done to an engine, power output will be increased. But if a series of things are performed, such as maximizing the air intake system, they can work together for better engine performance.

When it's time to put more muscle in an engine...

In order for an engine to turn at extremely high rpm (6,000+), the compression ratio and air flow in and out of the combustion chamber must be increased to the maximum. The secret to increased engine performance is to get as much air (and fuel) into the combustion chamber, and get it out as quickly as possible. (Remember - engine performance is entertainment to the spectators.) For the compression ratio to be increased, the air entering the combustion chamber must be squeezed as tight as possible.

The only things that can cause an engine to overheat and loose power are as follows:

• Clogged cooling fins or broken fins on the flywheel
• Too high compression ratio for the grade of gas being used
• Ignition timing advanced too much
• Lean fuel mixture
• Vacuum leak at the carburetor, which will also cause a lean fuel mixture.

Get Maximum Horsepower and Torque from a "Basically Stock" Kohler 10-16hp K-Series or Magnum Engine -

Approximately 48% more horsepower and torque can be produced from a basically "stock" single cylinder flathead Kohler engine. This means that approximately 15hp can be produced from a 10hp, 17hp from a 12hp, 20hp from a 14hp and 23hp from a 16hp governed engine at 4,000 rpm (the factory setting of maximum rpm for virtually all small gas engines, including all of Kohler engines is 3,600) on Premium gasoline! And if the majority of the fins are removed from the flywheel, or if a steel flywheel is used, this will add about 3-4 more hp per engine! Also, about 10% to 13% more power can be produced with E-85 or methanol fuels! Click here for information regarding E-85 fuel. The above figures was computed using Mr. Gasket's DeskTop Dyno computer application. (Do a search on the Internet for this application.) And even more power can be produced above 4,000 rpm! But be sure to install a billet steel flywheel, connecting rod and scatter shields whenever running an engine above 4,000 rpm! The compression ratio must be increased in order to increase the power output. Click here for references to various compression ratios. After modifications have been made, the increase in power will definitely be noticeable!

For pulling competition only, remove or disable the operation of parasitic accessories from the engine (which robs horsepower and causes drag on the engine), such as the starter/generator, alternator charging system, and including reducing the height of the fins by about 3/4 or removing all of the fins from the flywheel. (Personally, I use a reciprocating saw to remove about 3/4 of the height of the fins on our Kohler flywheels. And I ALWAYS have the flywheel dynamically precision spin-balanced afterwards!) The generator part of the starter/generator unit and the alternator system uses about 1-3hp of engine power when it charges the battery at a full 15, 20 or 30 amps with the engine running at 3,600 rpm. So to conserve this power for pulling, disconnect the generator or alternator from charging the battery (and powering other accessories as well) simply by splitting the wire that connects to the FIELD terminal (the smaller wire and terminal) on a starter/generator unit and splitting the wire that connects to the center terminal on the voltage regular of an alternator system. Then connect an ordinary OFF/ON toggle switch in that wire or circuit to turn off and on the charging current. And it'll be best not to spin the starter/generator when pulling. It can use up to 2hp just to spin it. Install a heavy spring on the generator/starter so it'll remain close to the engine. To start the engine, install the belt on the pulleys, then pull out on the generator/starter with a fabricated handle to tighten the belt. After the engine starts, flip the belt off. But use caution doing this for an obvious reason! The wasted energy that's needed to spin the starter/generator needs to be put to the ground. Besides, wouldn't it be better to spin the tires than the starter/generator?
Remove the flywheel fins ONLY if an engine is governed up to 4,000 rpm, and absolutely have a [cast iron] flywheel dynamically precision spin-balanced afterwards! If an engine is going to be operated well above 4,000 rpm (with no functioning governor), and rather if your pulling club's sanctioning rules require one or not, definitely install a steel flywheel (with no fins). Click here to see what can happen to an unaltered 9-1/2" diameter cast iron Kohler flywheel when spun well above 4,000 rpm.

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If you need any of the parts or services listed below, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA | Phone: 1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. Balancing Services - Balance flywheel (steel or cast) - $50.00 labor (mallory extra), plus return shipping & handling. Balance cast crankshaft - $125.00 labor (mallory extra), plus return shipping & handling. To balance an engine, I will need the crankshaft, piston/rings, pin, clips, connecting rod and bearing inserts. The flywheel is balanced separately. Balance steel crank - $150.00 and up (mallory extra), plus return shipping & handling.

Reground 4,000 rpm torque cast cam with stock lift and increased duration for stock 10-16hp flathead Kohler engines. This cam profile will pass tech for an OEM stock cam, but it adds about 3 more horsepower and 2 ft. lbs. of torque to an average stock engine with more lugging power than the 18hp cam. This cam sounds just like an OEM stock cam. You can't hear the difference out the exhaust. It's perfect for a competing stock pulling tractor or for ordinary yard work. To prevent breakage, use only OEM or light-weight Stock-Altered valve springs with this cam. This cam installs just like the OEM cam. Just thoroughly lubricate the inside with motor oil, align the marks on the gear teeth, set the end-play and valve clearance to OEM specs, and it'll be good to go. $150.00 outright, plus shipping & handling. $25.00 core charge, when you send us your stock OEM camshaft. Core must be in good condition, never reground before with no worn points lobe and gear teeth in good condition. When sending a core to us, be sure to include a note with your name, mailing address, phone number and that you want to trade the cam in as a core. I will then deduct $25.00 from the price of the torque cam. Please send your cam core to: A-1 Miller's Performance Enterprises, 1501 W. Old Plank Rd., Columbia, MO 65203 USA. More of our parts & services: Engine Rebuild Parts, Machine Shop Services, Engine Rebuilds & Build-up and Exhaust Header Pipe Kits

The cast iron camshaft that originally came in the Kohler model K361 18hp OHV engine is no longer available from Kohler. If you're lucky, you might find a new cam from old stock. The part number for this cam is 45 010 05S. They fit the 12, 14, 16hp flathead engines, too. Good for up to 4,000 rpm.) They work great in a stock engine!

The 18hp cam works great for increased power in a 10hp and 12hp engines, but it won't do quite as much in the 14hp and 16hp engine because of more cubic inches. Although it will work great in the 14hp and 16hp engines, but it creates less noticeable power increase in the 14hp and especially the 16hp engine. However, it does help in the power increase in a 16hp, it's just less noticeable because of the bigger cubic inch displacement. A "mild-performance" cam, such as the 18hp cam, works better in engines with smaller cubic inches. A somewhat bigger cam is required as the cubic inches are increased. Because bigger engines needs to draw in and expel more air (at 4,000 rpm with stock valves), and the 18hp cam has it's limits when used in the bigger engines. And because of it's short lift and duration, it makes it's most power up to around 4,000 rpm.

If you have a cam that was broke in two by a thrown connecting rod, save the hair-like or light-weight spring from the compression release mechanism. It can be used on another cam that may not have one.

Briggs and Stratton, Tecumseh, Onan and Kohler's cast iron block 7hp and 8hp, and the twin cylinder flathead engines are all somewhat limited on what can be done to boost their horsepower and torque. These engines are built from the factory to produce as much power as they possibly can, and still run safely on low octane gasoline. Therefore, very few modifications can be perform to help increase the power output. The only alternative is to use a bigger engine.

The increase in the compression will cause the combustion chamber to operate at a higher temperature. If low octane gas (87 octane) is used, and because low octane gas burns more rapidly than high octane gas, it'll burn hotter in a high compression engine, causing the piston and rings to overheat and wear out much sooner. Therefore, high octane gas (at least 91 octane [Premium]) must be used in a high compression engine because it burns slower and it maintains a cooler operating temperature within the combustion chamber. It'll help the engine last longer plus the high octane gas will help to produce more power. Also, it's safe to use just ordinary unleaded [high octane] gasoline with no additives (except what's already been formulated with the gasoline at the pump). Premium gasoline is the highest octane automotive gas you can get at your local filling station or convenience store.

High compression engines naturally operate at a higher operating temperature. So when using low octane gasoline (87 octane rating) in a high compression engine, the octane of the gas is reduced by 1 point for every 10º above the operating combustion chamber temperature that it is formulated for. This will cause the gas to burn faster and cause the engine to lose power. "Detonation" (pounding of the piston) could also occur. When trying to restart an overheated high compression engine on low octane gas, what is happening is the gas is burning quickly and entirely in the combustion chamber, and producing expanding heat before the piston reaches TDC, driving the piston back down in the cylinder before it reaches TDC. It'll cause the engine to "runt, runt" or momentarily make the crankshaft rotate in the opposite direction (but the weight of the flywheel prevents this from happening). Overheating could also crack the [cast iron] cylinder, shrink the piston, burn a hole in the piston (detonation) and weaken the expansion of the piston rings. Methanol fuel has an octane rating of 135. This is why methanol works best in high compression engines.

If you have a stock, low compression engine, then it won't benefit whatsoever from using high octane fuel. All it'll do is waste fuel (some of the fuel will go unburned and exit out the exhaust) and the engine won't develop full power, even with advanced timing. So it's best just to use low octane fuel for best performance.

In an ordinary engine that's built-to-factory-specs (with no modifications), it's OK to use just 87 octane gasoline. If you were to use high octane gas in a low compression engine, you'll just be wasting money and gas. Because some of the gas will go out the exhaust unburned, with no increase in horsepower whatsoever.

The initial setting for proper operation of the governor for stable engine speed is first loosen the clamp nut on the governor lever and rotate the shaft counterclockwise with the throttle in the full throttle position. Then tighten the nut. After you start the engine, run it a full (governed) speed and select the hole in the governor that allows the engine to run at 3,600 rpm.

Plastic governor gears works best if an engine will never run above 4,000 rpm. But if you're going to pull competitively with an engine and disconnect the governor to run the engine at wide open throttle, then it's best to install a cast iron governor gear. Because plastic will explode due to the increased rpm.

If you want to do away with the governor, you must remove it entirely from inside the engine block. Otherwise, at high rpm, the flyweights that's attached to the governor gear (which is called the "governor spool") will cause the plastic spool to explode. Or, you could disconnect the governor link from the carburetor and wire the arm to the exhaust pipe. This will prevent the governor spool from being damaged at high rpm. But then you must fabricate a throttle linkage of some kind to activate the throttle on the carburetor. For safety reasons, install a steel flywheel and crankcase side shields on an engine with no operating governor!

If you need even more power, remember the old saying? "There's No Substitute for Cubic Inches!"

If you're running a 10hp (K241) Kohler engine in a class that allows up to a 12hp engine, there's no need to go out and acquire a 12hp block, and then have all the fancy machine work that was originally done on the 10hp block. Instead, a 10 can be easily converted into a 12 by having the cylinder bored for a 12hp piston assembly, a 12, 14, 16 or 18hp connecting rod, and a 12hp crankshaft.

NOTE: Some 10hp Kohler engine blocks have K301 embossed in the casting on the PTO end. These blocks have a thicker cylinder wall and can be safely bored for a 12hp piston (even up to .030" oversize), without making the cylinder wall too thin. They cannot be bored for a 14hp piston though.

The K301 blocks with a 10hp bore can be safely bored for use with a 12hp piston. The K301 blocks are actually a 12hp block with a 10hp bore. There's nothing special about this blocks, except for the thicker cylinder wall. They weren't used in any "heavy duty" specific purpose either. What happened is on the production line at Kohler, when they ran out of 10hp blocks, they grabbed a bunch of 12hp blocks and bored them for use with a 10hp piston to finish the production of a bunch of 10hp engines. And not all Kohler blocks that have the K301 characters are actually 10hp blocks. Some are bored for a 12hp piston assembly (3.375" STD bore) and therefore, are a 12hp block. The ones that are bored for a 10hp piston assembly (3.250" STD bore) have a thicker cylinder wall and therefore, are a 10hp block. To determine which block is which, the diameter of the cylinder bore needs to be accurately measured.

How to Create a Stroker 10hp, or Generic Model "K261" Kohler Engine -

If the cylinder wall in a 10hp (model K241/M10) engine block is severely gouged or has excessive deep grooves and can't be bored enough to clean up for use even with a .030" oversize 10hp piston, and installing a sleeve for a standard size 10hp piston is too costly, then the block can be bored for use with a STD size 12hp (K301) piston/rings assembly. A 10hp connecting rod (a 12, 14, 16hp or 18hp ALCOA rod cannot be used for this purpose) and 10hp crankshaft is to be reused, creating a 26 cubic inch engine, a generic model K261, or a "de-stroked" 12hp engine. With a STD size [12hp] piston, this engine will have a 3.375" bore and 2.785" stroke. If built to stock specs, it'll produce about 11½hp at 4,000 rpm. But if it's built to the max, it'll produce about 16½hp at 4,000 rpm and 23 ft. lb. of torque at 4,000 rpm. For strength and durability, especially if it's built to the max, it's best to use a 10hp block with K301 embossed on the PTO end, like the one pictured above. These particular blocks have an extra thick cylinder wall. A 10hp crankshaft can also be used in a 14hp (K321/M14) or a 16hp (K341/M16) block, creating generic models K281 and K321. Here's how to make it happen: The big end of the connecting rod will need to be bored .070" offset toward the wrist pin hole so the piston will come flush with the top of the block. With the .070" offset, it's best to use a .010" undersize rod for a full circle cut. If using a STD size rod, use J-B Weld to fill in the uncut portion of the rod hole, allow the J-B Weld to fully cure (harden), then resize the hole so it'll be a perfect circle again. Or the rod can be bored .050" offset toward the wrist pin hole for a .020" piston pop-out. Bearing inserts will need to be installed. The wrist pin hole in the same rod will need to be enlarged to exactly .8755" for use with the 12hp (or 14, 16hp) piston's wrist pin. Being a heavier piston assembly is to be used, the crankshaft (rotating assembly) will need to be rebalanced, or the engine will vibrate severely and possibly self-destruct. This means that weight will need to be added to the counterweights on the 10hp crankshaft so the rotating assembly will be properly balanced. Click here to learn how to statically balance an engine. If building this type of engine for competitive pulling, check with your club's sanctioning rules so this type of engine will be legal within its class.

How to Create a De-Stroked 12hp, or Generic Model K271 Kohler Engine -

To create a model K271 Kohler engine, use a 10hp (K241/M10) block with a 10hp piston/rings assembly, and a 12, 14, 16hp [flathead engine] connecting rod or an 18hp OHV ALCOA rod (a 10hp rod cannot be used for this purpose) and a 12, 14, 16hp flathead or an 18hp OHV engine crankshaft. This combination will create a 27 cubic inch engine, a generic model K271, or a "stroked" 10hp engine. With a STD size [10hp] piston, this engine will have a 3.250" bore and 3.250" stroke. If built to stock specs, it'll produce about 12hp at 4,000 rpm. But if it's built to the max, it'll produce about 18hp at 4,000 rpm and 24 ft. lb. of torque at 4,000 rpm. For strength and durability, especially if it's built to the max, it's best to use a 10hp block with K301 embossed on the PTO end, like the one pictured above. These blocks have an extra thick cylinder wall. Here's how to make it happen: The big end of the connecting rod will need to be bored .080" offset toward the oil dipper so the piston will come flush with the top of the block. Or it can be bored .100" offset toward the oil dipper for a .020" piston pop-out. With either offset, it's best to use a .010" undersize rod for a more complete circle cut. Use J-B Weld to fill in the uncut portion of the rod hole, allow the J-B Weld to fully cure (harden), then resize the hole so it'll be a perfect circle again. Bearing inserts will need to be installed. The wrist pin hole in the piston will need to be enlarged to exactly .8755" for use with the 12, 14, 16hp flathead or 18hp OHV ALCOA rod's wrist pin, or the wrist pin hole in the rod can be reduced with a bronze bushing i.d. of .8594" (55/64") for use with the 10hp piston's wrist pin. Being a heavier crankshaft is to be used, the crankshaft (rotating assembly) will need to be rebalanced, or the engine will vibrate severely and possibly self-destruct. This means that weight will need to be subtracted from the counterweights on the crankshaft so the rotating assembly will be properly balanced. Click here to learn how to statically balance an engine. The lower sides of the cylinder wall may need to be clearanced (ground away) for the connecting rod due to the longer stroke. If building this type of engine for competitive pulling, check with your club's sanctioning rules so this type of engine will be legal within its class.

How to Build a 30 Cubic Inch (NQS Outlaw) Pulling Engine -

To build a "somewhat" competitive 30 cubic inch pulling engine, acquire a newer 12hp Kohler block with a large intake port, have the cylinder bored to .050" oversize for a 3.425" aftermarket (J&E or Arias) piston/rings assembly, and use a stock stroke (3.250") crankshaft. This bore and stroke combination calculates to 29.94 c.i. (Install a 1.8" offset intake valve and a 1.5" offset exhaust valve, big steel cam, billet head, and use a 44mm Mikuni carburetor with about an 8" long extension.) The piston and rod combination to use for this particular bore and stroke are as follows: Piston compression height of .875", with an aftermarket billet connecting rod of 6.125" in length will bring the piston flush with the top of the engine block. No rods are available for a piston pop out with this particular piston. Piston compression height of 1", with an aftermarket billet connecting rod of 6.000" in length will bring the piston flush with the top of the engine block. For a .062" pop out, use a 6.062" rod. For a .125" pop out, use a 6.125" rod. Piston compression height of 1.125", with an aftermarket billet connecting rod of 5.875" in length will bring the piston flush with the top of the engine block. For a .062" piston pop out, use a 5.937" rod. For a .125" pop out, use a 6.000" rod. But to build a truly competitive 30 c.i. pulling engine, use a 10hp/K241 Kohler block. (Acquire a 10hp block with K301 embossed on the PTO end, for strength and durability, like the one pictured above.) The cylinder will need to be bored to 3.300" and a steel crankshaft with a stroke of 3.500" will need to be used to build a stroker 29.94 cubic inch engine. (Install a 1.8" offset intake valve and a 1.5" offset exhaust valve, big steel cam, billet head, and use a 44mm Mikuni carburetor with about an 8" long extension.) The piston and rod combination to use for this particular bore and stroke are as follows: Piston compression height of .875" with an aftermarket billet connecting rod of 6" in length will bring the piston flush with the top of the engine block. For a .062" piston pop out, use a 6.062" rod. For a .125" pop out, use a 6.125" rod. Piston compression height of 1" with an aftermarket billet connecting rod of 5.875" in length will bring the piston flush with the top of the engine block. For a .062" pop out, use a 5.937" rod. For a .125" pop out, use a 6" rod. Piston compression height of 1.125" with an aftermarket billet connecting rod of 5.750" in length will bring the piston flush with the top of the engine block. For a .062" pop out, use a 5.812" rod. For a .125" pop out, use a 5.875" rod. Due to the small bore and long stroke, this combination produces more torque at high rpms (wide open throttle) than building a 12hp block with a .050" overbore and stock stroke (3.250") crankshaft. If the engine is built right, and if the correct camshaft and gearing is used, it'll give the competition a kick in their butt! No joke. Use the same size valves, cylinder head and carburetor as the stock stroke engine above. This bore and stroke combination is legal in the NQS's rules, as long as the cubic inch displacement does not exceed 30. With the 3.300" bore and 3.500" stroke, the cubic inches will be 29.94. But to be closer to 30 cubic inches, have a STD crank journal ground .015" offset, resulting in a .030" undersize journal, lengthening the stroke to 3.5075". The results with the 3.300" bore and a 3.5075" stroke, the cubic inches will be 29.999, which is slightly under the legal limit. Doing this will gain an edge over the competition. Click here for an explanation of why a longer stroke works better.

The NQS Outlaw 30 Cubic Inch Pulling Engine -

A "somewhat" competitive 30 cubic inch pulling engine is when a newer model 12hp Kohler block having a large intake port, the cylinder to be bored to .050" oversize for a 3.425" aftermarket (J&E or Arias) piston/rings assembly, and a stock stroke (3.250") crankshaft. This bore and stroke combination calculates to 29.94 c.i. A 1.8" offset intake valve and a 1.5" offset exhaust valve, .533" steel cam, billet head, and use a 44mm Mikuni carburetor with about an 8" long extension should be used. But a truly competitive 30 c.i. pulling engine is when a 10hp/K241 Kohler block is used. For strength and durability, especially if it's built to the max, it's best to use a 10hp block with K301 embossed on the PTO end, like the one pictured above. This particular block have an extra thick cylinder wall. The cylinder will need to be bored to 3.300" and a steel crankshaft with a stroke of 3.500" will need to be used to build a stroker 29.94 cubic inch engine. Install the same size offset valves, cam, carburetion and head as above. Because of the smaller bore and longer stroke, the combination above will produce more torque at high rpm (wide open throttle) than the 12hp block with a .050" overbore and stock stroke (3.250") crankshaft. Either engine can use the same size offset valves, camshaft, carburetion and head. If the engine is built right, and if the tractor is set up right, it'll give the competition a kick in their butt! No joke. This smaller bore and longer stroke combination is legal in the NQS's rules, as long as the cubic inch displacement does not exceed 30. With the 3.300" bore and 3.500" stroke, the cubic inches will be 29.94. But to be closer to 30 cubic inches, a STD size [steel stroker] crank journal can be reground .015" offset, resulting in a .030" undersize journal, lengthening the stroke to a maximum of 3.5075". The results with the 3.300" bore and a longer 3.5075" stroke, the cubic inches will be 29.999, which is just under the legal limit. Doing this will gain slightly more of an edge over the competition. Click here for an explanation of why a longer stroke works better.

Gain More Power and Torque by Moving the [16hp] Piston Closer to the Valves!

Only the OEM 16hp (K341) and 18hp OHV (K361) Kohler engine blocks, the center of the cylinder bore is offset .250" (1/4") with the centerline of the crankshaft main bearings. Because of the much larger bore, the piston is moved further away from the valves. On OEM pistons, the wrist pin is also located off-center .010" so they'll be less thrust (friction) on the cylinder wall, and this will allow the connecting rod to operate correctly. That's why these particular pistons have a notch in them indicating that the notch must face toward the flywheel.

In a high-performance 16hp engine, if the cylinder is bored in its original location (when the piston is installed off-center), and at high rpm, this will create a lot of friction in the area of the cylinder wall that's closest to the valves. To minimize or reduce this power-wasting friction, have the cylinder bored inline or centered with the center of the main bearings, or closest to the center of the main bearings as possible, depending on the diameter of the piston to be installed. More compression will be produced by doing this, too.

The best way to do this is acquire a [13 fin] 16hp block with an unworn, standard size cylinder. The reason it's best to use an unworn, standard size cylinder is for example, if a 3.825" (.075" oversized) diameter piston is going to be used, the cylinder will need to be bored .030" closer to the valves. The piston will then travel .030" closer with the main bearings. The piston still wouldn't be centered, but it'll be closer than the 1/4" offset. Larger diameter pistons may not be moved this close to the valves though. But it will help greatly in the performance characteristics.

The 13 fin 16hp block have a thicker cylinder wall than the 12 fin block. Therefore, a larger aftermarket piston/rings assembly can be used. And all 10, 12 and 14hp blocks have 13 fins. Only the "thin wall" 16hp block have 12 fins.

Here's something to think about: Between the factory-stock 12hp and 14hp engines, there's 2.19 cubic inches of difference. This means you get 2 more horsepower for that much difference. But between the stock 14hp and 16hp engines, there's a whopping 4.63 cubic inches of difference, for just 2 more horsepower! The reason for this is because the friction that the piston places against the cylinder wall in the 16hp robs the engine of valuable power. Kohler had to add more cubic inches just to get a maximum of 16hp out of their K341 engine at 3,600 rpm.

And if you're wondering, the cylinder bore is centered in all the [Jones, Julian, etc.] aftermarket blocks.

Do not attempt doing the above on the 10hp, 12hp or 14hp engines! The cylinder on these engines are bored centered with the centerline of the main bearings. Which should remain this way even for a pulling engine.

Is it worth it moving the piston in a 16hp Kohler?

Engines that use a piston or pistons with a notch have an offset wrist pin. The factory had to do this on a lot of big bore engine blocks because the cylinder bore is offset with the crankshaft main bearing centerline. To lessen wear on one side of the piston, the offset wrist pin allows the piston to operate straight up and down in the cylinder and not at an angle. If it can be done, then it's definitely worth moving the bore closer to the centerline of the main bearings. The aftermarket Stock Altered block has the bore in the stock location (.250" off of the centerline of the crank, toward the starter side of the engine) and is not centered like some must think. Most all the NQS S/A have the bores shifted closer to the valves. By doing this you end up with a tighter combustion chamber for more compression and power. We've done it for a long time on the stock Kohler blocks by offset boring the engine toward the valves, then pressing in a sleeve and offset boring the sleeve. You have to leave about .100 to .125 wall thickness on the sleeve on the valve side to maintain the strength. Depending on how far you move it, the sleeve will show between the fins between the valve box and jug. However, its cheaper just to buy the S/A block and offset bore that, the unfinished bore of a S/A block is only about 3 1/2" so you can offset it quite a bit and still get the bore to cleanup. I paid around $1,000 to sleeve and offset bore an original Kohler block, but it can be done. As far aftermarket blocks that have the bores center over the crank is the Pro/Super Stock blocks like the J2 and others. - This information was provided by Julian Stahl.

Why a Longer-Than-Stock Stroke Works Better For Pulling Competition -

Many people (pullers) believe that an engine will produce more noticeable power and torque simply by boring the cylinder and installing a maximum of .030" oversize piston/rings assembly. But there's no need to do this, and it won't give the engine anymore noticeable power. The best thing to do is just bore the cylinder to the next oversize, if needed. Or if it's worn beyond .030", have it sleeved back to standard size.

What makes an engine produce more noticeable power and torque is not necessarily a larger diameter piston, it's having a longer stroke. For example: there's a world of difference in power and torque between a 10hp Kohler engine into a 12hp Kohler engine. Unlike a strong 10hp, a healthy 12hp engine will actually pull you back in the seat when you punch the gas. This is because not only the 12hp has an 1/8" larger bore than the 10hp, but it has a much longer crankshaft stroke, 3/8" longer, to be exact! 12hp engines are able to produce 2 more horsepower than the 10hp because of three things: 1) 1/8" larger bore, 2) 3/8" longer stroke, and 3) higher compression ratio because the 12hp use the same cylinder head with the same size combustion chamber as the 10hp. But there's not really that much of a noticeable difference in power and torque between a 12hp and a 14hp engine, because the 14hp has an 1/8" larger bore, but it has the same length stroke as the 12hp. 14hp engines are able to produce 2 more horsepower than the 12hp because of two things: 1) 1/8" larger bore, and 2) higher compression ratio because they use the same cylinder head with the same size combustion chamber as the 12hp. Another example is the 7hp and 8hp Kohler engines. These are virtually identical in every way except for the length of the stroke. The 7hp has a stroke of 2.500", and the 8hp's stroke is 2.750". A 1/4" longer stroke (and higher compression due to the same cylinder head) results in 1hp more. Many new automotive engines nowadays have a small bore and long stroke. Simply because it works better!

A longer-than-stock stroke works better for more engine torque because at very high rpm (wide open throttle), it takes less time for the flame front (combustion) to travel down in the cylinder than it would to travel across the top of the piston. Therefore, due to the longer stroke, the fuel burns more thoroughly and the engine produces more power from the expanding gases of the burning fuel. For pulling competition, on a short stroke engine, at very high rpm and when the engine is under a load, some of the fuel will go unburned [out the exhaust] and loss of power will result. A short stroke engine works best for racing, but not for pulling. Racing engines and pulling engines are not built on the same principles. Racing engines require horsepower (speed) and pulling engines require torque (lugging power). This is why some "cheaters" in pulling run an illegal stroker engine in a class when they're not supposed to. As a result, on a biting track, when all the legal engines have run out of power, the stroker engine will keep lugging on out the gate. This is true for all engines, despite if it's a gas/alcohol burner, Diesel, 2- or 4-cycle. Return to previous paragraph È

If your club's rules allows a longer-than-stock stroke in any particular class, lengthen or increase the crankshaft's stroke slightly by grinding the crank journal .030" undersize with a .015" offset. Doing this will increase the stroke by .015". This would have to be done on an standard size, unworn journal. If the journal is worn, the amount of wear will have to be subtracted from the increase in stroke. Grinding the journal offset to increase the stroke is a way to slightly increase engine performance. It won't make a world of difference in engine performance, but it does help. Many professional high-performance engine builders do this to gain three things:

• Increase the cubic inches to the max according to the rules for more power and torque.
• Pop the piston out of the cylinder to increase the compression ratio.
• The smaller diameter journal will reduce friction at very high rpm. It'll allow an engine to turn freer, which will help to produce more power and torque.

Here's another thing to consider: half of the .015" increase in stroke is .0075". So .0075" plus the .020" offset rod adds up to .0275". Therefore, the piston will pop out of the cylinder at .0275". If the head was milled at .050", the clearance between the piston and head would be .0225". (.0275" - .050" = .0225".) This would still be a safe margin of clearance. The slightly longer stroke would help to increase the power and torque, PLUS the increase of the compression ratio with the .050" milling of the head (remove the raised ridge that mates with the head gasket) would help in power and torque, too.

Also, a 10hp block can be bored to use a 12hp piston and a 12 hp block be bored to use a 14hp piston, but this makes the cylinder wall very thin (approximately 1/8" thick). And it's safe to bore a K301 10hp block for use with a 12hp piston. If an ordinary block is not going to be used for pulling, it should be OK. But if it is going to be used for pulling, It is recommended that the cylinder be "strapped" to the crankcase to prevent the possibility of cylinder/crankcase separation, which can be a terrible event. Also, to maintain precision engine balance, a 14hp crankshaft must be used with the 14hp piston.

Personally, when I strap our engines, I don't install threaded rods in the block itself. Instead, I install an angled steel piece using the bolt holes on the PTO end of the block. Then I fasten a 1/2" threaded rod in it. And on the flywheel end, I weld a threaded rod to an 1/8" flat piece of steel and fasten it to the two upper bearing plate bolts. Because drilling holes and cutting threads in the block would be a lot more work and it wouldn't be any stronger.

And it's doubtful if a 14hp block can be bored for use with a 16hp piston. Some people have done this with success. But the center of the outer part of the cylinder may need to be offset one way or the other (not like in the 16hp block) to center the bore in the block as not to break through the cylinder wall during the boring process. If attempting this, it'll be a good idea to install a head strap rather it's for competitive pulling or general yard use.

Boring a 14hp engine to accept a STD size 16hp piston is a tricky process. First, you must find the "center" of the cylinder. This is done by measuring the outside of the cylinder to find the thinnest and thickest parts. If this isn't done, then the boring process could break through the thin part of the cylinder wall. And if the cylinder is bored offset, the wrist pin in the piston will allow the piston to be centered with the crank journal.

"Strapping" the cylinder to the crankcase is when a flat piece of heavy steel or aluminum is across the cylinder head and fastened by means of two minimum 1/2" diameter threaded rods, one located just behind the flywheel and the other on the PTO end of the block. It keeps the cylinder from literately breaking loose from the crankcase because of a thin cylinder wall and/or due to extremely high compression. Position the strap directly over (center of) the cylinder and not over the valve area.

And if there's no bolt holes on the PTO side of the block, then the block can be safely drilled and tapped on the PTO side for a head strap. Just be sure to drill the holes where there's most metal so you won't get into the crankcase. Torque the studs to 10 ft. lb. each.

The Correct and Professional Way to Sleeve a Cylinder:

NOTE: A sleeve can be successfully installed in a block even if the cylinder wall has a big chunk broke out of it due to connecting rod failure. And "resleeving" is removing the old sleeve and installing a new one. "Sleeving" a cylinder is installing a new sleeve when one wasn't already installed.

1. Acquire a cast iron sleeve that's slightly larger in diameter than the cylinder if a .030" oversized piston were installed. Make sure it's slightly longer than the overall length of the cylinder, too. (Virtually any place that sells pistons and rings offers cylinder sleeves, too.)
2. Bore the cylinder exactly .003" smaller than the outside diameter of the sleeve. The .003" interference fit makes for a perfect press fit. Do not make it any tighter or the cylinder could split or crack!
3. When boring the cylinder, leave an 1/8" ledge or "lip" at the bottom of the cylinder for the sleeve to butt against and not [possibly] work it's way down into the crankcase as the engine reaches its normal operating temperature.
4. Chamfer the lower outside end of the sleeve so it won't have a square edge.
5. Apply Loctite® Sleeve Retainer 640™ around the sleeve or in the cylinder, and using a hydraulic press, carefully and slowly press the sleeve into the cylinder until it bottoms out against the ledge. To ease installation of the sleeve into the cylinder, heat the engine block in an oven and cool the sleeve in a freezer. It should then just slip in without using a press. But this must be done quickly before the block cools and sleeve warms up.
6. Once the sleeve is installed, grind or machine the protruding upper part of the sleeve so it's even with the top of the engine block.
7. Bore or hone the sleeve for a standard size piston/rings assembly, and then chamfer the upper edge of the sleeve so the piston rings will slide in easy upon installation.
8. That's it! Virtually any machine shop that does machine work on automotive engines can install a sleeve in a Kohler engine block.

Advertisement:

If you need the cylinder(s) sleeved in your engine block, contact Elson Nichols of Loop 70 Auto Parts and Machine, 14 Business Loop 70 East, Columbia, Missouri 65201. Phone: 1-573-449-0893. E-mail: vjnen@centurytel.net. He has many years of experience in engine machine work and he can professionally sleeve your block and then bore it for a STD size piston/rings assembly.

If methanol is going to be burned in the engine, and because the engine will have a thinner cylinder wall with increased compression, It is highly recommended that the cylinder be fastened to the crankcase, to prevent the possibility of cylinder separation (or engine explosion).

As methanol burns, it produces tremendous combustion chamber pressures under full throttle (even more so on cooler days). To prevent possible cylinder/crankcase separation, the cylinder must be fastened to the crankcase with a fabricated clamp. Especially on 12hp engines and up. So strap it now, or scrap it later! Methanol works best in a high compression engine, too.

Moreover, if you had a 10hp block bored for a 12hp piston, or a 12hp block bored for a 14hp piston, and you use your tractor to push snow, definitely fasten the cylinder to the crankcase! Because it now has a much thinner cylinder wall, and the cold winter air is more dense (like the air is thicker or there's more of it). Dense air will build up the compression pressure within the combustion chamber, causing the engine to produce more power. But what also happens is at full throttle, this high compression is pushing upward on the cylinder head, and pulling upward on the cylinder wall. And sometimes the cylinder wall will break, ruining the whole engine. I know, we've had this happen before. No joke.

Actually, it's in the foreseeable knowledge of the laws of physics on how a successful pulling engine (and entire tractor) is built. Plus, it's the combination of tractor and driver working together as one that does well at the pulls.

If a bigger flathead engine still won't give you enough power, then use an overhead valve engine. They'll produce more horsepower and torque per cubic inch than any flathead engine ever will.

Maintain Crankcase Vacuum So Your Single Cylinder Engine Will Produce More Power!

When reinstalling the crankcase breather assembly on a single cylinder engine, make sure all the original components are reinstalled in the same order they were removed so that crankcase vacuum is maintained. (Click the drawing to the right for details. è) This is very important on any engine, especially a pulling engine. More horsepower will be created and the inside of the crankcase will stay cleaner longer. Dyno tests have proven that a single cylinder engine will produce more power with the reed plate (crankcase breather valve) installed. Without the reed plate on the old style valve cover, with the engine running and as the piston moves upward, air (and dust particles in the air) will be drawn into the crankcase through the valve cover hole. And as the piston goes back down, air will be forced out of the crankcase through the hole. This rapid "in and out" movement of air will rob a pulling engine of valuable power. Because air must be compressed through the small breather hole. Hot air (and the hot oil vapors) are supposed to be forced out of an engine, not sucked in. The reed plate keeps air from being drawn into the crankcase and the motor oil from being blown out. The piston will automatically vent the pressure on the downward stroke through the breather hole.

If motor oil has contaminated (and clogged) a new or good pleated air filter, there's no need to discard the filter and buy a new one. The oil can be dried out of the filter by soaking it in paint thinner (the thinner will mix equally with the oil), and then allow it to air dry. As it dries, the oil will dry out, too. Paint thinner can also be used to dry out oil that's spilled on a concrete floor. Just pour some thinner on the oil, use an old broom to mix the thinner with the oil, and eventually, the oil will dry with no signs of it ever being on the floor. Paint thinner is also known as cleaning solvent.

On the cast iron block 7hp and 8hp Kohler engines, the reed plate is installed with the reed valve facing outward or towards you. This allows air to escape out the crankcase, but no air can enter into the crankcase.

How the Reed Valve Works:

The underneath or backside of the piston creates a vacuum within the crankcase and valve spring compartment. When the piston goes down, air that's in the crankcase is forced out through the reed valve and cover hole, and when the piston goes back up, air wants to be drawn back in, but the reed valve prevents this from happening. Therefore, a vacuum is created and maintained within the crankcase. Air can only be forced out of the crankcase and not be allowed in. By the way - an automotive PCV (Positive Crankcase Ventilation) valve can be substituted for the reed valve. But most pulling tractors don't really need a PCV valve to maintain crankcase vacuum. Nothing will be gained by installing one. It'll just be for looks only. Besides, the reed valve design works excellent just the way the factory intended.

If there's a steady puff of smoke coming out of the crankcase breather, the reason for this is because the piston rings are worn. What is happening is a small part of the exhaust gases in the combustion chamber is bypassing the gaps in the rings, goes down in the crankcase and then out the breather. So it may time for a complete engine rebuild soon. If an engine rebuild is out of the question any time soon, what could be done to prolong the engine life a little longer is switch to 20W50 full synthetic motor oil for warm weather use.

Use an Auxiliary Crankcase Breather for Better Engine Venting Above 4,000 rpm...

The factory OEM crankcase breather alone isn't adequate for all high-performance single cylinder engines, especially big cubic inch engines running at all-out rpm. They build up more pressure in the crankcase due to the longer stroke and bigger piston. The downward movement of the piston will force air out of the crankcase. At very high rpm (well above 4,000 rpm), the small holes in the engine block and breather assembly sometimes aren't large enough for a sufficient amount of air to pass through or exit the crankcase. When air exits the crankcase through the OEM breather at very high rpm, it will sometimes take some crankcase oil with it, spewing an oily mess on the track, and probably on the tractor. So if your engine has this problem (not all engines spew oil at high rpm), and to keep this from happening, your engine needs an auxiliary crankcase breather. It helps to relieve some of the air pressure inside the crankcase that's placed on the stock breather assembly. But by looking at the picture to the right, you'll notice that this is an open breather system with no one-way check valve to prevent air from re-entering the crankcase. Relax. This is how it works: the faster a single cylinder engine revs, the less time air has to exit and re-enter the crankcase. In other words, at very high rpm, and being air can be compressed as well as it can be expanded, it cannot re-enter the crankcase through the auxiliary breather simply because there isn't enough time for it to do so. Therefore, the crankcase maintains zero vacuum. The auxiliary breather also has a filter in it. This is to prevent dust and dirt from entering the crankcase at low rpms.

The auxiliary crankcase breather doesn't help to make more horsepower. It just keeps oil off the track and inside the engine.

Advertisement: (posted 1/27/11)

If your engine needs an auxiliary crankcase breather kit, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA | Phone: 1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. For better engine venting and less oily mess above 4,000 rpm. Kit includes street elbow, short pipe fitting, 12" vinyl tubing, clamp and MOPAR breather. NOTE: For Kohler blocks, use a 3/4" NPT taper pipe tap to cut threads in the block to install the pipe fitting. For aftermarket blocks, use a 1" NPT taper pipe tap to cut threads in the block to install the pipe fitting. Sold below. Ê Auxiliary Crankcase Breather Kit: $30.00 each, plus shipping & handling. 3/4" NPT taper pipe tap. Made of quality carbon steel. $21.00 each, plus shipping & handling. Part # WT0321-0025 1" NPT taper pipe tap. Made of quality carbon steel. $27.00 each, plus shipping & handling. Part # WT0321-0030 More of our parts & services: Engine Rebuild Parts, Machine Shop Services, Engine Rebuilds & Build-up and Exhaust Header Pipe Kits

Checking for a Worn Piston -

If there's oil on the top of a piston, then this means that the piston and rings are badly worn. Piston rings operate in a particular manner. The top ring holds the compression. The 2nd ring is the oil scraper. It flexes as it travels up and down in the cylinder. It glides over the oil on its way up and scrapes the oil on it's way down. When installing new rings, if the 2nd ring came with an expander, install it under the ring. It helps to stabilize the piston in the cylinder. And the oil ring assembly is the lubricator. It lubricates the cylinder wall and other rings so they'll last longer. All new or unworn piston rings have a square edge. If the piston skirt becomes worn in a cylinder, this will cause the piston to "wobble" in the cylinder. Which will cause the square edge on the rings to become "rounded" and then the 2nd ring won't be able to scrape the oil on its way down. Instead, it brings the oil to the top of the piston (past the gap in the top ring)

Speaking of a worn piston, if your engine makes an uneven "clattering" sound when running or especially when under a load, then perhaps the piston is loose or worn in the cylinder bore. To check this, remove the cylinder head, and with the piston positioned at TDC, forcibly and quickly move the piston side to side by hand (side thrust of the crankshaft). If you hear a "slap, slap" sound, then the piston is badly worn.

According to Kohler's specs, when using an OEM or aftermarket piston in an engine, the piston-to-cylinder wall clearance should be no less than .007" and no more than .010". But make it tighter for pulling (.007"). Because OEM pistons will wear slightly when used in a high rpm application. As for a forged, high-performance piston (Arias and J&E), when hot, they will swell more than an OEM piston. Therefore, requiring slightly more clearance. Most high-performance pistons require a .010"-.014" clearance. But check with the manufacturer of the piston for the exact clearance.

If you had the cylinder in your engine block bored oversize, before installing the piston/rod assembly in the cylinder, always clean the cylinder wall with warm soapy water and use a clean cloth that's white in color to see and to remove the microscopic metal dust that get lodged in the cross-hatch honing process of the cylinder wall. (Machine shops do not do this.) The metal will, more than likely, cause the rings to wear prematurely if this is not done. After cleaning, allow the cylinder to air-dry.

The Correct Way to Install Piston Rings -

Lubricate the wrist pin with clean motor oil, and then install the connecting rod on the piston. NOTE: If the piston has a notch on the top (16hp and 18hp OHV engines), install the rod to the piston with the oil hole in the cap facing toward the camshaft. Make sure the match marks are aligned on the rod and cap!

Next, install the rings on the piston in their correct order according to the provided instructions or refer to the drawing to the right for correct piston ring installation. è

Installation of rings on the piston are as follows:

1. The oil lubricating (bottom) ring(s) goes on first.
2. The oil scraper (middle) ring goes on second.
3. Then the compression (top) ring goes on last.

Never attempt to install piston rings in reverse order or they might break upon installation! Install the rings in the order as follows: (The below applies to all 4-stroke small air- or water-cooled engines, automotive, tractor, heavy equipment engines, etc.)

1. The bottom ring(s) usually have no particular (upward or downward) way of installing, as they don't flex either way. If it's a three-piece ring, the expander installs first and butts end to end. The ends do not over-lap. The expander "expands" the two thin oil lubricator rings so they can apply more pressure against the cylinder wall to work better.
2. Make sure the middle ring is installed correctly! This step is very important! This particular ring actually flexes as it "scrapes" the oil from the cylinder wall on its way down and glides over the oil on its way up. If this ring isn't installed correctly or right-side-up, the engine will smoke and use a lot of oil. For most middle rings, the bevel (inside angle) faces downward. For a chrome-edge second ring, the bevel faces upward. But if there's a dot (punch mark) or the word TOP laser-etched on the ring, it faces upward. If the middle ring came with an expander (rippled spring-like ring), install it under the second ring. It helps to stabilize the piston in the cylinder.
   • NOTE: If the middle ring is installed wrong side up, and if the engine smokes (a lot), this ring can be removed and reinstalled right side up. It can be reused because very little wear has occurred to it. There is no need to purchase another new set of rings due to improper installation. Because installing new rings incorrectly doesn't necessarily cause them to wear more, they just cause the engine to smoke out the exhaust.
3. And as for the top ring, if it has square edges with no bevel, then there's no certain way how it installs on the piston, being it just holds the compression. And just like the second ring, if there's a dot (punch mark) or the word TOP laser-etched on the ring, it faces upward.

Instructions on how to install the rings should be in the box they came in. And if you're wondering if there's any certain "tricks" when installing chrome rings on the piston or breaking them in, well, there really isn't any. Just install them as you would with ordinary cast iron rings. Being chrome rings are made of much harder material, it just takes longer for them to seat, they hold up to heat better, and they last a lot longer. Go here for more information: http://www.totalseal.com/howdoo.html.

There is really no need to stagger the ring gaps 180° on the piston upon installation in the cylinder. Being rings swell as they get hot due the normal friction against the cylinder wall, the rings actually rotate slightly on the piston as the engine runs. But if it'll make you feel better, go ahead and stagger the gaps anyway.

Being piston rings get extremely hot at high rpm (at wide open throttle), they swell or expand, a lot!. So before installing the rings, be sure to set the ring gaps at .025". Fit each ring squarely in the cylinder and use a feeler gauge to accurately measure the gap. Grind the ends of the rings until the proper gap is acquired. Failure to do this will cause the rings to swell up in the cylinder and result in a scored cylinder wall. The ring gaps won't need to be widened for stock engines that will run no faster than 4,000 rpm.

After the engine block has been thoroughly cleaned and dried, before installing the piston/rings/connecting rod, use a generous amount of clean, lightweight motor oil or automatic transmission fluid to lubricate the cylinder wall, piston and rings, as well as the rod bearing and crank journal. Never use a "spray lubricant" such as Liquid Wrench or WD·40 on any internal parts to assemble a fresh engine! Spray lubricants are too thin and will cause premature wear to the bearings, piston, rings and possibly the cylinder wall! Instead, apply clean motor oil on all of the parts that make contact with each other. And ALWAYS apply oil inside the camshaft, on the camshaft pin! If the engine is going to be in storage for a long period of time, grease or chassis lube can be used instead of oil for the camshaft pin and on the rod/crank journal. The reason grease works better for storage is because oil will eventually drain off the parts, allowing a "dry engine startup" which could damage valuable parts.

When installing the piston and rings in the cylinder, the 10hp, 12hp and 14hp Kohler pistons installs either way because the wrist pin is centered in the piston. But if the [OEM] piston has a notch, such as the 16hp flathead and 18hp OHV single cylinder cast iron block engine pistons, these install with the notch facing toward the flywheel end of the block. And to lessen the chance of blow-by, don't forget to stagger the ring end gaps 180º. Then use a quality-made piston ring compressor or if a ring compressor isn't available, a ring compressor can be fabricated out of clean (no paint, rust, etc.) 2" x 14" x 16 gauge steel sheet metal (heating duct tin works excellent) with a large adjustable radiator hose clamp to compress the rings. And be sure that everything is absolutely clean before installing the piston assembly in the cylinder!

Use a heavy wooden dowell or the wooden or rubber end of the handle of a medium-sized hammer to gently drive the piston into the cylinder. Be sure that the connecting rod is aligned with the crank journal as the piston is driven into the cylinder! If the piston stops going into the cylinder for any reason, stop to see what is stopping it. Don't just keep pounding it!

Piston ring technology has progressed a lot in recent years. Many ordinary small engines and automotive engines nowadays have thinner rings, and the rings place less tension against the cylinder wall. This is mainly to improve fuel economy and reduce exhaust emissions. It also helps the engine produce more power. Also, the engine idles smoother and revs up quicker.

Chrome VS Cast Iron Rings -

Some ring sets comes with the top ring having a chrome outer edge. Personally, I never experienced any differences between using a chrome ring or a cast iron ring. It seems that as long as the oil is changed regularly, a clean air filter is installed and the engine runs cool, one ring lasts just as long as the other. Because incoming dirt in the air intake system and in the oil, and overheating of the combustion chamber are the biggest killer of quality piston rings.

Wrist Pin Retaining Snap Rings -

For high performance use (especially wide open throttle operation), use [the proper size] internal snap rings instead of the OEM retaining clips to retain the wrist pin in the piston. Because OEM retaining clips can wear excessively and on rare occasions, they've have been known to come loose at high rpm.

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If you need a new ring set or a new piston/rings assembly, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA | Phone: 1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. More of our parts & services: Engine Rebuild Parts, Machine Shop Services, Engine Rebuilds & Build-up and Exhaust Header Pipe Kits

OEM-type ring set for Kohler 4hp engine models K90, K91. Also replaces BRIGGS & STRATTON Part # 294232, 295657, KOHLER 220801, 220801S, CLINTON 233112500, 233122500. Cylinder Diameter: 2.375". Available in standard size only. Made of high grade cast iron for durability. $15.00 each set, plus shipping & handling. OEM-type ring set for 7hp (K161) and 8hp (K181) Kohler K-series flathead engines with the newer 2-15/16" bore. The top ring is a proven cast design with a chrome edge for long life, proper lubrication and scuff-free service. The 2nd ring is a reverse torsion type for sealing. Finally, the oil ring is the famous 'Flex-Vent' 3-piece design, which exerts uniform pressure on the cylinder wall while providing 200% more drainage capacity than conventional one-piece oil rings. Available in STD, .010", .020" and .030" oversizes. Made of high grade cast iron for durability. NOTE: The model K141 Kohler engine will need to be bored to 2.9375" to accept these new style rings because the rings for the 2-7/8" bore are no longer available. And this ring set fits the early style piston only. They will not work with pistons with the word "Mahle" stamped on them. Check your piston carefully before ordering. STD. size: $35.00 each set (for one piston). .010", .020" and .030" oversizes: $45.00 each set (for one piston). OEM-type ring set for 10hp-16hp and 18hp OHV Kohler K-series flathead engines. Same specs as above. Available in STD, .010", .020" and .030" oversizes. Made of high grade cast iron for durability. Note - This ring set fits the early style piston only. They will not work with pistons with the word "Mahle" stamped on them, or high performance aftermarket pistons (Arias, JE, etc.). Check your piston carefully before ordering. 10hp (K241) STD size: $30.00 each set (for one piston). .010", .020" and .030" oversizes: $40.00 each set (for one piston). 12hp (K301) STD size: $35.00 each set (for one piston). .010", .020" and .030" oversizes: $45.00 each set (for one piston). 14hp (K321) STD and .010" each set: $40.00 each set (for one piston). .020" and .030" oversizes: $50.00 each set (for one piston). 16hp (K341) and 18hp (K361) STD, .010", .020" and .030" oversizes: $35.00 each set (for one piston). OEM-type ring set for Kohler flathead engine models KT17, KT17II, M18, M20, MV16, MV18 & MV20. Replaces Kohler: 52-108-01, 52-108-09-S. Available only in standard size. $25.00 each set (for one piston).

OEM-type piston, wrist pin, retaining clips and OEM-type ring set for Kohler K-series and Magnum 7hp (K161) and 8hp (K181/M8) cat iron block flathead engines with a 2-15/16" bore. Rings are made of cast iron; top ring has a chrome edge. Available in STD, .010", .020" and .030" oversizes. NOTE: The model K141 Kohler engine will need to be bored to 2.9375" (2-15/16") to accept this bigger piston and rings because the piston/rings for the 2-7/8" bore are no longer available. And being the wrist pin is centered, this piston can be installed in either direction. $40.00 each, plus shipping & handling. OEM-type piston, pin, clips and OEM-type ring set for Kohler K-series and Magnum 10hp (K241/M10), 12hp (K301/M12) and 14hp (K321/M14) cast iron block flathead engines. Rings are made of cast iron; top ring has a chrome edge. Available in STD, .010", .020" and .030" oversizes. Compression height: 10hp - 1.63"; 12hp & 14hp - 1.7". And being the wrist pin is centered, this piston can be installed in either direction. $50.00 each, plus shipping & handling. OEM-type piston, pin, clips and OEM-type ring set for Kohler and Magnum 16hp K341/M16 cat iron block flathead engines and Kohler K-series 18hp K361 OHV single cylinder engine. Rings are made of cast iron; top ring has a chrome edge. Available in STD, .010", .020" and .030" oversizes. Compression height: 1.7". Wrist pin is offset to reduce piston slap. Therefore, piston installs with notch towards flywheel. $80.00 each, plus shipping & handling. NOTE: High-quality OEM-type ring sets, pistons and piston/rings assemblies are also available for other makes & models of small gas engines. And the piston assemblies that I sell will work with a stock connecting rod and crankshaft without the need for rebalancing. And always use a billet connecting rod of the correct length with an aftermarket piston (Arias or JE) that has the right compression height. These two parts must be matched for the piston to come flush with the top of the engine block, or have a few thousands of an inch pop out. If using an OEM piston and rod, these parts will not interchange with a longer-than-stock billet rod or with an OEM-type of piston of a different compression height, and vice-versa.

NOTE - I can get complete engine rebuild kits, but a kit cost us more than if I were to order the parts individually. So please contact us with a list of which parts you need, and we'll get back to you with a total including shipping & handling. And if you need a part or parts that's not listed here or for other make and model of engines, please contact us and we'll see if I can get it at a reasonable price. Please contact us if you're interested in any of the above parts or items.

"Popping" the Piston Out of the Cylinder -

"Popping" the piston out of the cylinder a few thousands of an inch by offsetting the bore in the connecting rod and installing bearing inserts, decking the block or using a custom piston and connecting rod combination will improve air flow and raise the compression ratio within the combustion chamber for more power and torque. Remember, when popping the piston out of the cylinder, there must a minimum of .030" clearance between the cylinder head and top of piston! To determine the distance between the cylinder head and piston, first measure the thickness of the compressed head gasket, and then subtract .030" for clearance. It may be necessary to machine the underneath area of the [billet] head directly over the piston to obtain the .030" safety clearance. Also, the edge of the piston must be ground away for improved combustion. See further below. Ê

If there's inadequate piston to cylinder head clearance, the piston will hit the head, without a doubt. If the engine is able to crank over and run, this will be evident by a loud tapping sound in the engine. A series of events will then soon happen: As the piston continues to strike the head, this will crush or flatten the soft metal coating (babbitt material) in the upper half of the bearing insert in the connecting rod, causing the rod to knock. But the knocking sound probably wouldn't be heard due to the piston hitting the head. Or there will be a "double knock." At very high rpm (wide open throttle), the looseness of the "flattened" bearing will cause the rod bolts to stretch. This will happen even in an aftermarket 4-bolt billet rod. But a stock OEM rod will probably just break. This could also cause the crankshaft to bend (or break), rather if it's made of cast iron or steel. If the engine is ran continually at high rpm, eventually the connecting rod will break, or the bolts in an aftermarket billet rod will break and the rod cap will become disconnected from the rod, which will likely destroy the engine block.

Most 10hp (K241) pistons, and some other Kohler engines, don't come flush with the top of the engine block at TDC. Therefore, if installing bearing inserts and you want the piston to pop out of the cylinder a few thousands of an inch, the piston must first be placed in the cylinder without rings with a crankshaft journal at TDC, and then the piston height accurately measured. If you choose to pop the piston out of the cylinder, you must take into consideration the piston height and how far you want the piston to pop out of the cylinder. Example: If the piston comes within .020" of the top of the block and you want the piston to pop out at .020", then the big end of the rod must be offset-bored at .040". By the way - most competitive pulling engines have the piston pop out of the cylinder.

The OEM head gasket has a compressed thickness of about .050". The piston and cylinder head needs to have a safety margin (clearance) of .030'. Therefore, with a milled head, the piston needs to pop out at a maximum of .020".

If you choose to use a piston and connecting rod combination that comes flush with the top of the cylinder, decking the block a maximum of .020" will allow the piston to pop out of the cylinder approximately .020". The stock head gasket is approximately .050" thick when compressed. Therefore, this will allow the .030" of the required clearance between the cylinder head and piston. In addition to decking the block, the valve seats will have to be re-done and proper valve lash adjustments must be made.

The compressed thickness of an OEM Kohler head gasket is about .050". The piston needs to have a safety margin of .030" due to rod stretch and crankshaft flex at very high rpm. And yes, when properly balanced, even a cast iron crankshaft will flex a few thousands of an inch at high rpm without breaking.

The edge of the piston will have to be ground away with the piston in the block and connecting rod attached to the crankshaft. Otherwise, the edge may be too high or too low with the top of the engine block. And if the piston is going to be popped out just .020", there's no need to grind the edge away.

Removing Metal From the Edge of the Piston For Improved Combustion:

1. Place the crankshaft in the block along with the bearing plate.
2. With the rings off the piston, slide the piston, connecting rod with the bearing into the cylinder.
3. Rotate the crankshaft so the piston is at the TDC position.
4. Use a felt marker to place a line on the side of the piston next to the deck which face the valves.
5. Remove the piston, and use a disc or belt sander to grind off the mark and grind an angled edge on top of the piston about 3/8" back. Create about a 30º angle or smooth the grinding so it'll blend in with the top of the piston. The grinding should resemble a "crescent moon" shape on the piston.
6. Finally, use fine sandpaper to smooth and polish the ground edge.

Here's two interesting web sites: Arias Pistons (http://www.ariaspistons.com/) | J&E Pistons (http://www.jepistons.com/).

New high-performance piston and ring assemblies are available from Lakota Racing (http://www.lakotaracing.com/), Midwest Super Cub (http://www.midwestsupercub.net/) and Vogel Manufacturing Co. (http://www.vogelmanufacturing.com/). They offer them in various sizes and compression heights. They also make billet connecting rods to match the compression height of the piston and stroke of the crankshaft.

What does "Compression Height" of a Piston Mean?

The compression height is the measured distance from the top of the piston to the center of the wrist pin. The stock 10hp Kohler piston has a compression height of 1.62", and the stock 12 through 18hp Kohler pistons have a compression height of 1.7". When the wrist pin is located lower in the piston (this is known as "high compression height"), a shorter connecting rod must be used with the piston for it to come flush with the top of the engine block.

The differences between the OEM 10hp and 12hp, 14hp and 16hp Kohler pistons, rods and crankshafts:

• The 10hp piston has a compression height of 1.62". The rod when measured from the centerline of each hole is 5.558" in length. The crankshaft has a stroke of 2.875".
• The 12hp, 14hp and 16hp piston has a compression height of 1.7". The rod when measured from the centerline of each hole is 5.3" in length. The crankshaft has a stroke of 3.25".
• The 10hp, 12hp, 14hp and 16hp Kohler blocks all have the same deck height, which is 8.625" (when measured from the centerline of the main bearings to the top of the block.)

Many high-performance pistons have the wrist pin located closer to the top of the piston. (This is known as "low compression height.") With a high-performance piston with the wrist pin located closer to the top, a longer connecting rod must be used with the piston for it to come flush with the top of the block, or a slightly longer rod is used for the piston to pop out of the cylinder a few thousands of an inch. The reason many professional engine builders prefer to use a longer connecting rod is because they can pop the piston out of the cylinder, plus reduce the friction that the piston skirt places against the cylinder wall at very high rpm.

Why Having Proper Crankshaft End Play or End Clearance Is So Important -

On virtually any engine, crankshaft end play (clearance) is a few thousands of an inch when the crankshaft can move side to side (horizontal shaft engines) or up and down (vertical shaft engines). Inadequate crankshaft end play can have an effect on the crankshaft main bearings and engine performance.

Having proper crankshaft end play controls the stability of the piston in the cylinder, lessens wrist pin wear, lessens ring wear and it lessens connecting rod bearing surface wear on the crank journal. On a vertical shaft engine, if the crankshaft has too much end play, the piston will operate diagonally (at an angle) in the cylinder. This diagonal movement of the piston will cause the rings, wrist pin and rod bearing surface to wear unevenly and prematurely. But on a horizontal shaft engine, if the crank has too much end play, the piston and connecting rod will wobble side to side in the cylinder (much like the clapper in a bell). At high rpm, the crankshaft can move back and forth so quickly, the wrist pin in the piston couldn't react quick enough to compensate for the excessive movement. Also, on engines such as the cast iron block Kohler with helical (angled) teeth on the crankshaft and camshaft gears, too much crankshaft end play will effect the valve timing, which in turn will effect engine performance.

In a Kohler engine, insufficient crankshaft end play will cause the main bearings to overheat and "tighten up" and produce a "whine" or "howling" sound at higher rpms. The overheated bearings could also cause the engine to slow down for no apparent reason at high rpm when the [petroleum] motor oil reaches it's normal operating temperature.

In an engine that has ball bearings as main bearings, the steel balls in the main bearings turn the same speed as the crankshaft. If there's insufficient crankshaft end play, and the faster the crankshaft spins, the balls in the main bearings will spin just as fast, and despite having quality lubricating oil in the crankcase, the balls get hot, sometimes very hot. And the so-called high-performance aftermarket 11- or 12-ball main bearings operate even hotter. When this happens, they swell a few thousands of an inch. If they swell too much, crankshaft end play is taken up and crankshaft binding occurs, which effects engine performance. This is why it's so important when rebuilding or building an engine to set the proper crankshaft end play to specifications. I found that the OEM Kohler 8-ball main bearings works better in either a factory-stock or in a high performance or high rpm engine. Just like the factory-built Chevy V8 engines, Kohler engineers knew what they were doing when they designed the internal parts for their engines.

The gaskets on the bearing plate of a Kohler engine are also shims to adjust the crankshaft end play. Add or subtract gaskets until the proper clearance for crankshaft end play is obtained. Use a feeler gauge between the crankshaft and one of the main bearings or a dial indicator on the end of the crankshaft to check the end play clearance. To set the clearance, install one or two thick (.030") and/or one or two thin (.015") gaskets between the crankcase and bearing plate until the desired clearance is obtained. The end play on the 10-16hp flatheads and the 18hp OHV Kohler single cylinder engines is .003" (for very low rpm engines) to .020" (for very high rpm engines). Personally, I like to set the crankshaft end play anywhere between .012" - .020". I don't like the "closeness" of the .003" - .011" of clearance. The engines I build seems to turn freer at higher rpms with the little more clearance.

Sometimes when a Kohler engine is reassembled, it will take several gaskets to achieve the proper crankshaft end play. And as long as the bearing on the PTO end is fully seated and the crankshaft is more or less butted against the bearing, the [OEM cast] cam timing will be in perfect alignment.

Why Do Some Main Bearings Fit Tight on a Kohler Crankshaft and Others Have a Slip-Fit?

I've rebuilt many Kohler engines through the years, and it seems that with all of them, either the crankshaft main journals were machined a few thousands of an inch different, or the main bearings were machined different. Either way, with some engines, when installing the crankshaft, I have to drive the crank into the PTO bearing and sometimes I have to drive the front bearing plate on, too. But with other engines, the crank just slides into each bearing.

Being a machinist, I know that cast iron and steel contracts a few thousands of an inch in cool temperatures and expands a few thousands of an inch in warm temperatures. With this fact, being their old manufacturing building probably wasn't insulated that well, it would seem that Kohler machined (ground) some of their crankshafts (and/or bearings) on a cool day and others were machined on a warm day (summer and winter months). This would explain why there's a few thousands of an inch difference with the main journals on their crankshafts. Either that, or they were machined on an early Monday morning, or late Friday afternoon.

Anyway, to adjust the crankshaft end play, set it according to Kohler's specs. Use a heavy wooden or leather mallet to bump the crank back and forth so you can get a feeler gauge between the PTO bearing and crank to measure the end play clearance. And despite if the main bearings fit tight on the crank, as long as the end play is set right, the engine should run fine.

If all the oil were cleaned from the Kohler crankshaft main [ball] bearings with cleaning solvent and allowed to thoroughly dry, and then if the bearings were spun by hand, and if the bearings isn't worn much or at all, they will make a rattling sound. The noise isn't necessarily because the bearing is worn, the noise is caused by the balls running dry on the races (metal to metal contact) because there's no oil to separate the two. Apply a small amount of motor oil to the balls/races and then spin the bearings by hand. They should be a lot quieter now. The same thing will happen with new bearings. And if the bearings have very little free play in them (about .005"), like they're worn, don't worry about this. As the engine rpms increases and when the motor oil warms up, the balls in the bearings will expand. Even new bearings have little play in them for this reason. If all bearings, new or used, had no free play, as they get warm up, the balls would bind in the races, lessening the performance of the bearing.

Information About Using the Correct Connecting Rod for the Job -

If you've ever wondered about the differences between the old K-series connecting rods and the new style [Magnum engine] rods, the sides of the wrist pin hole on the new style rod are machined narrow so it can fit inside the new style Mahle piston. A new style rod will fit both the older K-series pistons and Mahle pistons without modification, but the K-series rod will fit only the K-series pistons. If you want to use a K-series rod with a Mahle piston, the sides of the wrist pin must be ground narrow so it'll fit in the Mahle piston.

The best OEM connecting rod to hold up well above 4,000 rpm for use in a 12, 14 and 16hp engine is the one made for Kohler's 18hp OHV (K361) engine. The 18hp rods are much stronger than the 16hp (K341) rod, and more expensive. These rods should hold up well as long as the piston assembly and rod are precision balanced to the crankshaft's counterweights. Because no rod is indestructible when it comes to high speed out-of-balance rotating parts.

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If you need a new or used connecting rod for your 10hp, 12hp, 14hp or 16hp engine, or if you wish to have your 10hp-18hp connecting rod fitted with bearing inserts, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA | Phone: 1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. More of our parts & services: Engine Rebuild Parts, Machine Shop Services, Engine Rebuilds & Build-up and Exhaust Header Pipe Kits

There's "match marks" on both the rod and rod cap. They MUST be aligned or "matched up" so the big end of the rod forms a perfect circle around the crank journal when installed. Otherwise, if the cap is installed backwards, the "perfect circle" will be egg-shaped or oblong, which will bind on the crank journal. DO NOT over-tighten the rod bolts! Upon installation, the oil hole in the cap faces toward the camshaft. And if the threads strip out in a rod, then perhaps a longer grade 8 fine thread bolt can be installed in reverse (the rod will need to be machined for head bolt clearance) and use a grade 8 nut. If not, then the rod is junk.

6¼ & 7hp Connecting Rod - New STD size 6¼ (K141) & 7hp (K161) K-series flathead engine connecting rod. Replaces Kohler part # B-230039-S. This is a plain aluminum bearing surface rod. Bearing inserts are not available for this particular rod. Standard size: $84.00 each, plus shipping & handling. .010" undersize: (no bearing inserts) $63.00 each, plus shipping & handling.

8hp Connecting Rod - New STD size 8hp (K181 & M8) K-series and Magnum flathead engine connecting rod. Replaces Kohler part # 41-067-10. Comes with split lockwashers under head bolts. This is a plain aluminum bearing surface rod. Bearing inserts are not available for this particular rod. Standard size: $32.00 each, plus shipping & handling. .010" undersize: (no bearing inserts) $35.00 each, plus shipping & handling.

10hp Connecting Rod - New STD size connecting rod for 10hp (K241, M10) K-series and Magnum flathead engine. Replaces Kohler part # 47-067-13; comes with a long dipper. Strong rod. Comes with split lockwashers under head bolts. This is a plain aluminum bearing surface rod, but I can bore rod and install bearings if you wish. 5.558" length. Standard size: $35.00 each, plus shipping & handling. .010" undersize: (no bearing inserts) $48.00 each, plus shipping & handling. Used STD size connecting rod for 10hp (K241, M10) K-series and Magnum flathead engine. Replaces Kohler part # 47-067-13; comes with a long dipper. Strong rod. Comes with split lockwashers under head bolts. This is a plain aluminum bearing surface rod, but I can bore rod and install bearings if you wish. 5.558" length. $20.00 each, plus shipping & handling. (When available.) 12hp and 14hp Connecting Rods - New "one color" connecting rod for 12hp (K301, M12) and 14hp (K321, M14) Kohler K-series and Magnum flathead engines. Replaces Kohler part # A-237344, 45-067-09, 45-067-09S; comes with a long dipper and 3/8" thread-in bolts. Strong rod. Comes with split lockwashers under head bolts. This is a plain aluminum bearing surface rod, but I can bore rod and install bearings if you wish. 5.3" length. STD $40.00 each, plus shipping & handling. .010" $45.00 each, plus shipping & handling. Used "one color" STD size Genuine OEM Kohler connecting rod for 12hp (K301, M12) and 14hp (K321, M14) Kohler K-series and Magnum flathead engines. Kohler part # A-237344, 45-067-09, 45-067-09S. Comes with long dipper and 3/8" bolts or studs w/"Posi Lock" nuts. Strong rod. These were in stock engines that never exceeded 3,600 rpm for a long period of time. Comes with split lockwashers under head bolts. This is a plain aluminum bearing surface rod, but I can bore rod and install bearings if you wish. 5.3" length. $30.00 each, plus shipping & handling. (When available.) Used "two color" STD size Genuine OEM Kohler connecting rod for 12hp (K301, M12) and 14hp (K321, M14) Kohler K-series and Magnum flathead engines. Genuine Kohler part # A-237344, 45-067-09, 45-067-09S; comes with a long dipper and 3/8" thread-in bolts, good for up to 4,000 rpm. These were in stock engines that never exceeded 3,600 rpm for a long period of time. Comes with split lockwashers under head bolts. This is a plain aluminum bearing surface rod, but I can bore rod and install bearings if you wish. 5.3" length. $20.00 each, plus shipping & handling. (When available.) 16hp Connecting Rod New 16hp (K341, M16) Kohler K-series and Magnum flathead engine connecting rod. This particular rod is narrow at the wrist pin so it'll fit inside the 16hp piston. Replaces Kohler part # 45-067-22, 45-067-22S; comes with a long dipper and 3/8" thread-in bolts. Strong rod. Comes with split lockwashers under head bolts. This is a plain aluminum bearing surface rod, but I can bore rod and install bearings if you wish. 5.3" length. STD $50.00 each, plus shipping & handling. .010" $55.00 each, plus shipping & handling. Used 16hp (K341, M16) Kohler K-series and Magnum flathead engine connecting rod. This particular rod is narrow at the wrist pin so it'll fit inside the 16hp piston. Kohler part # 45-067-22, 45-067-22S. Comes with long dipper and and 3/8" bolts or studs w/"Posi Lock" nuts. Strong rod. These were in stock engines that never exceeded 3,600 rpm for a long period of time. Comes with split lockwashers under head bolts. This is a plain aluminum bearing surface rod, but I can bore rod and install bearings if you wish. 5.3" length. $25.00 each, plus shipping & handling. (When available.)

Machine Work for Connecting Rod - Narrow wrist pin area on 12hp or 14hp rod for use with a 16hp piston. Click image to the right. $20.00 labor, plus shipping & handling. Bore and notch 10hp-18hp cast iron block single cylinder Kohler connecting rods for installation of bearing inserts: $25.00 labor, plus shipping & handling. Clevite 77 bearing inserts available only in STD, .010", .020" undersizes. $15.00 each, plus shipping & handling. Federal Mogul bearing inserts available only in .030" undersize. $25.00 each, plus shipping & handling. Bearing inserts are available in STD, .010", .020" and .030" undersizes. Please let me know if you want the bearing centered in the bore of the rod (piston flush with top of block) or offset .020" or more (up to .125" at no extra charge) to pop the piston out of the cylinder (click image to the right) to raise the compression and help improve air flow within the combustion chamber for more power and torque. The bearing inserts we install in Kohler connecting rods can be used for ordinary yard work or pulling competition.

To identify this particular type of rod, they look a lot like Kohler's 12hp, 14hp and 16hp OEM rods, but they're of a very bright aluminum color. The word "ALCOA" and the numbers "45 564 01" (which isn't the correct part number) are embossed in the beam section. If you're planning to use one of these rods in a 12, 14 or 16hp engine, just remember that the crankshaft doesn't need to be rebalanced for use with it because it weighs the same as the other OEM rods. But do have it fitted with bearing inserts. But if you'd like to have them balanced anyway, it might help the engine run somewhat smoother. Return È

Most "part numbers" on Kohler connecting rods are meaningless. It seems that they're just random numbers that Kohler put on their rods. Why they did this, I have no idea.

The second best Kohler-made connecting rod to hold up to around 6,000 rpm in the 12, 14 and 16hp engines are the ones made for Kohler's 16hp flathead engines. They are of one color and have a "slick" or shiny surface. Kohler's correct part number for this rod is 45-067-22. This is for a standard size crank journal. The correct part number for a .010" undersize rod is 45-067-23. If a standard size rod is used with an undersized crank journal, the engine will make a loud knocking sound at operating speeds and eventually rod failure will result. So be sure the rod is matched to the crank journal. And it's doubtful that a two-color rod (light gray at the wrist pin and dark gray at the crank pin) will hold up in a "built to the max" stock engine or in an engine running without a governor. But they seem to hold up very well with no problems in ordinary governed engines running at 4,000 rpm. By the way - any connecting rod that's going to be operated above 4,000 rpm should be fitted with bearing inserts. Also, if an OEM or Kohler-type rod is used, rebalancing of the crankshaft to the rod/piston isn't necessary. Aftermarket or high-performance (heavier than stock) rods MUST be balanced to the crankshaft's counterweights. If an engine isn't balanced for use with an aftermarket rod, the engine will vibrate severely and eventually self-destruct. Click here for engine balancing.

Torque the 10hp through 18hp connecting rod having the 3/8-24 bolts to 285 in. lb. or 24 ft. lb., and torque the studs w/nuts to 260 in. lb. or 22 ft. lb. For the cast iron block 7hp and 8hp engines, torque the rod bolts to 200 in. lb. or 17 ft. lb. DO NOT OVER TORQUE! And with the match marks aligned on the connecting rod and the cap, the rod goes in the cylinder with the oil hole in the cap facing toward the camshaft.

If a Kohler (or aftermarket) rod that has bolts (not nuts), originally came with a flat washer under the head bolts, replace the washers with split lockwashers of the appropriate size. After installing the rod in the engine, torque the bolts to specs. The split lockwashers will guarantee the bolts will not loosen over time. This is especially important in an engine that runs at wide open throttle. (Added 1/6/12)

There's "match marks" on both the rod and rod cap. They MUST be aligned so the big end of the rod forms a perfect circle around the crank journal when installed. Otherwise, if the cap is installed in reverse, the "perfect circle" will be egg-shaped or oblong, which will bind on the crank journal. And DO NOT over-tighten the rod bolts, or the rod and cap will become distorted. If this happens, the rod will need to be honed back to the proper dimensions in a rod honing machine. And the oil hole in the cap faces toward the camshaft.

Be aware - as with any engine running above 4,000 rpm, there is no guarantee that an OEM "one color" rod will not break. A "one color" rod only lessens the chances of it breaking. Actually, it's best to use a custom-made billet connecting rod and have the piston assembly and connecting rod precision balanced to the crankshaft's counterweights. Click here to learn about precision engine balancing.

How Bearing Inserts Protect An Engine -

Due to lack of lubrication in the crankcase, and/or at very high rpm, an ordinary aluminum bearing surface connecting rod will most likely score the crank journal, and if the engine is ran long enough with a loose rod, the rod will likely break, possibly destroying the engine block. But an engine with bearing inserts, if the oil is contaminated with dirt or metal shavings, or if the engine is ran low on oil, out of oil or if the wrong viscosity is used (too thin of oil for warm weather conditions or for high-performance use), as the bearings wear, they won't score the crank journal like an ordinary aluminum bearing surface rod will. In most cases, a rod with bearing inserts will knock, but rarely cause the rod to break. If the engine starts knocking, turn it off immediately and replace the damaged bearing inserts, and then install the proper grade/weight of oil to the full level. Sometimes the bore in the rod can become oblong or "egg-shaped" after taking a pounding from a worn bearing. If this happens, it will need to be resized in a connecting rod honing machine to make the bore a perfect circle again. If a new bearing is used in a rod with an oblong hole, the bearing may fit too tight on the crank journal, causing it to get hot while in use and possibly burn out from inadequate oil clearance. With bearing inserts, the crank journal may also wear, but most likely not wear. It'll also be wise to check the rod for stress cracks with a strong magnifying glass or better yet, a powerful microscope.

As long as the crankcase is full of oil (splash oil lubrication system) or adequate oil gets to the bearings (pressurized oil pump lubrication system), and as long as the bearing inserts have adequate oil clearance, bearing inserts will hold up to unlimited engine rpms. You'll also have more confidence knowing your engine has bearing inserts. Return to previous paragraph. È

Upon installation of a connecting rod in a Kohler engine, the oil hole in the cap faces toward the camshaft! There's "match marks" on both the rod and rod cap. They MUST be aligned or "matched up" so the big end of the rod forms a perfect circle around the crank journal when installed. Otherwise, if the cap is installed backwards, the "perfect circle" will be oblong or "egg-shaped," which will bind on the crank journal. And DO NOT over-tighten the rod bolts or nuts! If the threads strip out in a rod, then perhaps a longer grade 8 fine thread bolt can be installed in reverse to serve as a stud (the rod will need to be machined for head bolt clearance) and use a grade 8 nut. If this cannot be done, then the rod is scrap metal.

Connecting rods, rather being OEM or aftermarket (stock or high-performance), and despite how well-balanced the rotating parts are in a pulling engine, suffer a lot of stress at high rpm in a single cylinder engine. Therefore, if possible, before purchasing a used rod, it's best to look it over for hairline cracks with a strong magnifying glass or better yet, a microscope. And as I always say about buying anything off of eBay: BUYER BEWARE! So ask for a money-back guarantee, or you may have nothing but a piece of scrap metal on your hands.

If using a stock connecting rod above 4,000 rpm, the aluminum bearing surface should never be used. Because the extreme pressure and heat from the rapid rotation of the rod on the crankshaft journal causes the aluminum to swell and this could cause the oil clearance to lessen making the aluminum have contact with the crankshaft, minimizing the oil clearance, which will overheat and become scored, resulting in crankshaft journal/rod scoring or burning, engine seizure or even rod breakage. One way around this, if bearing inserts isn't available for your particular rod, is to have the rod surface enlarged an additional one thousands of an inch (.001") to allow for additional oil clearance (the extra .001" of clearance will not cause the rod to knock) and to make room for the aluminum to swell when it gets hot. Or if your rod can accept bearing inserts (10hp-16hp Kohler rods), have automotive-type bearing inserts installed, even if the rod is new or used, or if it has a relatively good bearing surface. The reason bearing inserts work best in high-performance or heavy duty conditions is because the soft babbitt material (lead) that's on the inserts can withstand extreme heat and extreme pressure. It also "cushions" the impact that the rod places on the crankshaft journal at high rpm. And it's still a good idea to have an additional .001" of additional oil clearance, even if bearing inserts are used. Using bearing inserts also strengthens a [stock] rod by cushioning the severe impact the rod places on the crankshaft at very high rpm.

No connecting rod in any 10hp-16hp K-series Kohler engine come from the factory with bearing inserts in them. The rod must be machined (bored and notched) for installation of bearing inserts. Kohler don't make bearing inserts for the connecting rod in any of their single cylinder engines. The bearing that's used in the rods are actually made for one particular model of Continental Engines, model 469 (4 cylinder). But the bearings fit the Kohler rod perfectly after it's been bored out. The bearings are available in STD, .010", .020" and .030" undersizes. Also, these bearings can only be used in Kohler engines with a 1.500" diameter crankshaft journal/crank pin (or undersizes), such as the 10hp through 18hp single cylinder engines and all of their twin cylinder engines with a stock (OEM) or an aftermarket connecting rod. No bearing inserts that I know of is designed for use in any other Kohler engines, except for the Kohler engine models K482, K582 and K682 if the crank journals were reground to 1.500". (STD size is 1.625".) The connecting rods would not need to be bored, being they are already 1.625" in diameter. But they would need to be notched for the tangs on the bearing inserts.

For high rpm use, bearing inserts also need additional oil clearance. Therefore, it's good insurance to have the crank journal ground an additional .001" for extra oil clearance. As the rod and journal swell due to the rapid rotation of the two parts, metal to metal contact won't happen. Of course, it's a good idea to use full synthetic oil, too. And once a journal's been reground to exactly .010", it's awful hard to ground an additional .001" on it, making it .011" undersize. If the journal has been ground to exactly .010", the rod would need to be honed an extra .001" instead.

Sometimes an OEM connecting rod will need to be bored for installation of bearing inserts when the crank journal must be reground deeper than .010" undersize. (STD and .010" OEM connecting rods are the only two sizes that's available from Kohler.) But bearings are available in STD, .010", .020" and .030" undersizes, to match the reground journal. If your crank journal needs to be reground to .020" or .030" undersize, then undersized bearing inserts will need to be installed in the rod to match the diameter of the crank journal. Bearings can only be installed in the 10-16hp single cylinder flathead Kohler engines, the 18hp OHV single cylinder Kohler engine, the Series 2 19hp twin cylinder Kohler engine and the 20hp Magnum engine, because these engines all have a 1-1/2 diameter crank journal. Bearing inserts also help to provide longevity of the journal, just like in automotive engines.

More Information About Bearing Inserts -

For pulling applications, the oil clearance between the rod bearing and crank journal should be .0035" with ± .0005" for wear. This allows the .001" more clearance for rod swelling (when hot; only at high rpm). It'll be good to use this clearance for stock engines, too.

Bearing inserts provide a little more oil clearance to protect the crank journal. If checking the oil clearance with PlastiGage, and if it shows the clearance to be .0032"-.0035", don't worry about it. It'll work just fine. Many race cars run this much clearance. The rod won't knock either.

Boring a Kohler rod and installing bearing inserts in it doesn't weaken the rod whatsoever. Because whenever a rod breaks, 99% of the time they break in the beam section, not around the bearing area. And bearing inserts add very little weight. Meaning they don't upset the balance of the piston/rod assembly to the crankshaft's counterweights a great deal, even at very high rpm.

Installing bearing inserts in a rod for a Kohler engine would cost much less than purchasing a new or even used rod and/or crankshaft, even when used for non-pulling applications. Bearing inserts can be installed in new or used rods. They can also be installed in rods that's scored, has a heavily burnt surface (the burnt material will need to be bored out anyway to make room for the bearing), or even if the rod has a mismatched cap! If installing a mismatched cap, be sure to align the match marks, and it'll be best to resurface the sides of the big end on a sanding disc slightly (with the cap torqued to the rod, of course) to insure proper fit and side clearance on the crank journal.

By the way - We've reground MANY Kohler crankshafts to .020" and .030" undersize and installed bearing inserts in connecting rods and I have never had any problems with the crankshaft breaking, even when used in pulling competition when the engine turns at 6,000+ rpm. So it's a safe thing to do. Besides, I wouldn't have mentioned it here if it didn't work.

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If you need a set of bearing inserts, or bearing inserts installed in your connecting rod, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA | Phone: 1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. Machine Work for Connecting Rod - Narrow wrist pin area on 12hp or 14hp rod for use with a 16hp piston. Click image to the right. $20.00 labor, plus shipping & handling. Bore and notch 10hp-18hp cast iron block single cylinder Kohler connecting rods for installation of bearing inserts: $25.00 labor, plus shipping & handling. Clevite 77 bearing inserts available only in STD, .010", .020" undersizes. $15.00 each, plus shipping & handling. Federal Mogul bearing inserts available only in .030" undersize. $25.00 each, plus shipping & handling. Bearing inserts are available in STD, .010", .020" and .030" undersizes. Please let me know if you want the bearing centered in the bore of the rod (piston flush with top of block) or offset .020" or more (up to .125" at no extra charge) to pop the piston out of the cylinder (click image to the right) to raise the compression and help improve air flow within the combustion chamber for more power and torque. The bearing inserts we install in Kohler connecting rods can be used for ordinary yard work or pulling competition. More of our parts & services: Engine Rebuild Parts, Machine Shop Services, Engine Rebuilds & Build-up and Exhaust Header Pipe Kits

If a rod burns on the crankshaft in an engine, the causes are either:

• Too low oil level.
• Oil dipstick calibrated wrong.
• Oil dipper broken off of connecting rod.
• Too high engine rpm for a plain aluminum surface rod.
• Insufficient oil clearance between the rod and crank journal.
• Insufficient oil clearance between the rod and crank journal for a high-revving engine.
• Rod installed backwards.
• Rod cap installed on the rod backwards.
• Mismatched rod and cap.

NEVER, EVER INSTALL A CONNECTING ROD DRY! Always lubricate the cylinder wall, piston rings, piston pin, bearing surface and crank journal thoroughly with clean motor oil before installing! Failure to do so could (or more likely, will) result in prematurely worn rings, piston, rod journal damage or seizure, crank journal damage and possible engine block damage!

Ever wondered why there's longer-than-stock length custom-made connecting rods?

The reason many high-performance engine builders prefer to use a longer, custom-made, billet [heavy duty] connecting rod is because there's less pressure from the piston skirt placed against the cylinder wall during high rpm. At high rpm, a long rod moves or "swings" side to side with less force, while a stock length rod moves more rapidly. Longer rods operate at less of an angle than shorter stock rods do. Therefore, piston skirt "drag" or scraping and force against the cylinder wall is greatly reduced and an engine will produce more rpm with less friction resulting in more power. In order for an engine to accommodate a longer rod, a special made light-weight piston with its wrist pin located closer toward the top (wrist pin location is known as "compression height") must be used. Many engine builders prefer to pop the piston out of the cylinder a few thousands of an inch to help increase compression. To do this, either offset bearing inserts are installed in a stock rod, or a longer rod/custom piston combination is used.

Because billet connecting rods are wider than OEM ones, each lower side of the cylinder wall must be ground away with a small disc grinder so the rod will clear it. The minimum clearance between the rod and cylinder wall is .050".

The billet connecting rod bolts should be torqued to 18 to 20 ft. lb. Overtorquing them could result in distortion of the big end of the rod.

NOTE - When used in a high rpm application, aluminum connecting rods develop "rod stretch" over time, which could lead to rod failure. Even if it's a custom-made one. So to be safe, measure a used rod against a new or a known good one, or replace it after several years of use. And the connecting rod in ordinary lawn and garden engines will outlast the rod in high performance engines because there's less strain on them at 3,600 rpm.

And if you've ever wondered about this: the bolts and studs in Kohler connecting rods can be reused over and over. They're very durable. Besides, nobody makes replacement bolts or studs for Kohler rods.

When installing the connecting rod and piston assembly in your engine, it's very important that the hole in the rod cap face the camshaft for proper lubrication of the rod journal. If it's installed facing away from the cam, the rod could burn. Also, both the connecting rod and cap are machined to form a perfect circle around the crank journal. So make sure that you install the connecting rod in the right way because both the rod and cap must be matched for proper fit around the crank journal.

A knocking or rattling sound in an engine can occur from several different places. Here are the most likely causes:

1. Worn connecting rod and/or crankshaft rod journal. To check for a loose rod and/or worn journal, with the piston halfway in the cylinder, very gently rotate the flywheel (or crankshaft) back and forth by hand. If the rod/journal is worn, you'll feel it. You can feel when the piston comes up on the compression stroke by the resistance of the flywheel when rotating it. This is when it compresses air. And there'll be no resistance when the piston reaches TDC. So before or after it reaches TDC, this is when you can check for looseness of the rod on the crank journal.
2. Loose fitting piston in the cylinder. To check for a worn or loose piston, with the cylinder head removed and the piston positioned at TDC on the compression stroke (when both valves are fully closed), forcibly move the piston from side to side by hand. If the piston has a lot of play, you'll hear a knock-knock sound.
3. Too much crankshaft end-play. To check for this, grasp the PTO end of the crankshaft or flywheel with your hand and forcibly move the crankshaft back and forth. If there's too much end-play, you'll see it and hear it.
4. Worn balance gear bearings. To check for worn balance gear bearings, first remove the oil pan, and then move the balance gears side to side by hand. They may not make any noise when moving them by hand, but if they're excessively loose, they will make noise with the engine running. These can be removed without removing the crankshaft or rod/piston. With them removed, the engine will not vibrate any more than before. A heavy duty, angled-shaped, expandable snap ring pliers is required to remove the snap rings that holds the balance gears in place. Be sure to remove the thrust washers and spacers (if present), too. Leave the stub shafts intact. They will not interfere with anything.
5. A loose PTO pulley or electric clutch on the crankshaft. To check these, with the engine not running, grasp the pulley or clutch by hand and forcibly move it/them back and forth. If there's too much play, you'll hear it.
6. A loose flywheel or worn Cub Cadet clutch disc will also cause a knocking or rattling sound.

By the way - Main bearings in a Kohler engine wear extremely little, if any at all, and don't require replacing. Although I have seen some that are obviously worn and needed to be replaced. And worn main bearings won't make a knocking sound. They'll make a rumbling or growling sound because the crankshaft and flywheel will be spinning out-of-balance and the engine will have a more than-usual-vibration.

Is your engine leaking and burning oil?

Check for oil leakage around the sump cover gasket. Sometimes the engine block will become warped from normal engine heat and a small part will pull away from the sump (especially under the cylinder). When this happens, part of the gasket will be sucked inside the crankcase. This will make an air gap which allows air to be sucked into the crankcase upon every upward movement of the piston. Then the air will become compressed upon the downward movement of the piston. This buildup of compressed air inside the crankcase will force the motor oil past the piston ring gaps and cause the engine to smoke, burn oil.

Gaskets: Should you use sealant or not?

If the parts isn't warped (where the metal is raised between the bolt holes), you need no sealant on the gaskets. But if they are warped, it'll be best to apply some sealant. To fix a warped part, resurface it on a flat belt sander or sanding disc.

What Type of Motor Oil Should Be Used? Top of page

Oil Recommendation:

• SAE 30 for 40° F and higher (5° C and higher) is good for all purpose use above 40° F, use below 40° F will cause hard starting.
• 10W30 or 10W40 for 0° to 100° F (-18° to 38° C) is better for varying temperature conditions. This grade of oil improves cold weather starting, but may increase oil consumption at 80° F (27° C) or higher.
• Synthetic 5W30 for -20° to 120° F (-30° to 40° C) provides the best protection at all temperatures as well as improved starting with less oil consumption.
• 5W30 for 40° F and below (5° C and below) is recommended for winter use, and works best in cold conditions.

In an older or freshly rebuilt air-cooled, lawn and garden engine with splash lubrication or if it has an unfiltered oiling system with no oil pump and/or no oil filter is used, it's best to use SAE 30 weight non-detergent motor oil. Non-detergent oil allows any impurities in the oil to settle to the bottom of the oil pan. Detergent oils suspends any impurities so the oil filter can better filter it. Detergent oils should be used only in engines with an oil filter. If an engine doesn't have an oil filter, it's best to use non-detergent oil for long engine life. If an engine is used during wintertime, and being there are no multi-weight or synthetic non-detergent oils available, the only option is the use 10W30 or 10W40 motor oils so the engine will crank over easy in cold weather to start fast. And be sure to change the oil when it's hot on a regular basis.

Rule of thumb is: Detergent oils should be used only if the engine has an oil filter. Because the debris in the oil is suspended in detergent oils, which can be filtered, with non-detergent oil, the debris settles to the bottom of the oil pan. But if the oil changed on a regular basis, detergent oils can be used in a non-filtered oiling system. What was mentioned above is what most manufacturers suggest to use [non-detergent oil] in their non-filtered small engines, which does make sense. And you know as well as I do that nothing lasts forever in this world. And despite what kind of oil is used, eventually all engines will wear out sooner or later.

If you think about it, most pulling tractors don't run long enough (compared to race cars) to totally heat the oil and break it down so it's thin. But if it makes you feel any better, it's safe to use SAE 50 oil instead. Due to the extreme pressure of the internal moving parts at high rpm (above 4,000 rpm), don't use multi-weight oils such as 10W30 or 10W40. They could cause excessive wear, resulting in damage to internal parts. I've used SAE 30 at times then SAE 50 in our two Super-Stock tractors and have had good results with both oils.

But if you don't mind spending a few extra bucks, the best type of oil to use in a pulling application to use is full synthetic SAE 20W50 motor oil. Test data shows that you can get a 1 to 2 percent increase in horsepower using full synthetic oil. There's also a less chance of a full synthetic oil leaking because it doesn't "thin out" as easily as petroleum oils, especially under extreme heat conditions. Because extreme heat has little or no effect on chemical-based products such as full synthetic oil, RTV silicone sealer, etc., it doesn't break down like natural-based products sometimes do. Once you understand the properties of full synthetic oil vs petroleum oil, you will never use petroleum oil again. And either type of oil may need to be changed periodically if burning methanol fuel. Amsoil has a 20W50 and a straight 60 weight for racing/high performance applications.

Using a full synthetic oil will allow an engine to run cooler, operate smoother and last longer. Petroleum oils get hot and their additives break down after a while, and if not changed regularly, sludge will form. Full synthetic oils never get hot. They stay cool to the touch the entire time while in the engine and their additives don't break down. Therefore, no sludge. It's really amazing how well full synthetic oils work. For a newly rebuilt engine, SAE 30 weight oil should be used for break-in so the parts will form a wear pattern, then after 2 hours of use, switch to 10W30 (for stock engines) or 20W50 (for high performance engines) full synthetic oil.

Synthetic oil is mainly used in high-revving and high-performance engines that operate at higher rpm for long periods of time because full synthetic oil won't get hot like petroleum oil does, which protects the internal moving parts better. But mineral oil, which is more commonly known as petroleum oil, is used in ordinary engines that will never operate at extremely high rpm for long periods of time.

Full synthetic motor oil remains cool to the touch even after an engine has been operated for several hours. The viscosity remains the same, too. Petroleum or mineral motor oil gets hot and the viscosity breaks down after a while if the oil is not properly cooled. But there's also a synthetic blend type of motor oil that's 30% synthetic and 60% petroleum. They don't offer the same protection that full synthetic oil do.

Basic rule of thumb concerning motor oil is this: Rub some between your finger tips. If it feels too thin, chances are it won't provide the needed protection for your engine.

Also, I think using oil additives don't do a thing for an engine. Because without an oil filter, an engine will wear out faster than an engine with an oil filter. Besides, if oil refineries thought that an additive would help an engine last longer, they would put it in their oil. Additives is just something to get people's money, nothing more. What works best in an unfiltered engine (no oil pump/filter), is glue a small magnet at the bottom of the oil pan to attract metal shavings for longer engine life. But make sure the oil dipper on the connecting rod doesn't make contact with the magnet!

If a carburetor floods or if the ignition timing is too retarded, the excess or unburned gas will seep past the piston ring gaps and into the oil, contaminating and diluting it. When oil becomes diluted, excessive internal wear will result. The gas will also break down the additives in the oil, causing sludge. This is why it's so important to have a "fine tuned engine" and change the oil regularly.

If "piecing together" a 10-16hp cast iron block single cylinder Kohler engine from various parts off of other engines, remember, the oil dipstick and/or tube may not be the right one for a particular engine. I've found several dipsticks and/or dipstick tubes that's not calibrated to certain Kohler engines. Some are too short and some are too long. This includes the ones that mount on the side of the block, next to the gear starter, or on top of the crankcase, next to the cylinder, but not the one that mounts over the cam gear (cam gear cover dipstick).

If the dipstick is too long or the tube is too short, the engine won't have enough oil in the crankcase, which could eventually lead to disaster. And if the dipstick is too short or the tube is too long, the engine will have too much oil, which could blow out the crankcase breather atmospheric vent hole at higher rpm. Also, make sure that the "end cap" or "stop cap" is properly positioned on the dipstick. If it slipped out of position from normal wear, this will give an incorrect oil level reading, which the oil level will actually be too low. If it did slip, the cap will need to be realigned (calibrated) and tack-welded back in place.

To fix a loose fitting oil dipstick tube, remove the tube, and use something tapered or a flared socket to spread the end of the tube slightly. Then before reinstalling the tube, apply Loctite® Threadlocker Red 271™ (available at virtually any auto parts store) to secure it in place in the aluminum holder.

Checking the Accuracy of the Oil Dipstick -

The engine is at full capacity of oil at 3/8" above the oil pan gasket for the 7hp and 8hp Kohler engines, and 1/2" above the oil pan gasket for the 10hp-16hp Kohler engines. If in doubt about the accuracy of the dipstick, hold the dipstick on the outside of the block with the cap (on the dipstick) even with the top of the dipstick tube or the threads on the dipstick even with the top of the crankcase (where the crankcase meets the cylinder) and then see if the FULL mark on the dipstick is at 3/8" or 1/2" respectively, above the oil pan gasket. If it's not, then an adjustment to the dipstick needs to be made. This method removes all guesswork. And always fill an engine with oil to the FULL mark on the dipstick.

But for a competitive pulling engine, ask yourself these two questions: How many times does one have to add oil to a pulling engine? And as long there's no major oil leaks, why have a dipstick? Just know how much oil your engine holds, and have a way on the engine block to install the oil after every oil change. Return È

Performing a Compression Pressure Test on a Stock or High-Performance Engine -

An accurate compression reading can't be performed on a stock engine with an unaltered OEM camshaft due to the compression release mechanism on one of the cam lobes. The compression release (or relief, as it is sometimes called) is either a small lump (B&S, some Tecumseh, etc.) or mechanical lever/pin (Kohler, some Tecumseh, etc.) on one of the camshaft lobes that holds either the exhaust or intake valve open about .050" while the piston is traveling halfway up in the cylinder on the compression stroke. On OEM camshafts with a working compression relief mechanism and if the valves are adjusted to specs, the compression relief releases about half the compression from the combustion chamber at cranking speeds. This is so the engine will start easier with fixed advanced ignition timing. If the compression release isn't working or if the valves are out of adjustment (too much stem to lifter clearance), the engine would "kick back" every time when trying to start it due to the fixed advanced ignition timing.

To obtain an accurate compression pressure reading, perform the test with a fully charged battery, a starter that's in good condition and the throttle in the wide open position. Or with pull rope engines, place the throttle in the wide open postion. When performing a compression test with a gauge on an air-cooled engine, keep in mind that, depending on how the engine is built, the compression ratio or the compression pressure can vary a lot from one engine to another. It depends on the size of the bore and stroke, the volume of the combustion chamber in the cylinder head, if the camshaft has a compression release or not and how much duration the cam lobes have. If a cam has a compression relief mechanism, the compression reading will be cut in half.

When performing a compression test on a 10hp Kohler engine, it can range anywhere from 98 to 150 psi. On a 12hp, it can be from 112 to 170 psi. On a 14hp, it can range from 120 to 190 psi. And on a 16hp, it can be from 127 up to 192 psi.

And cranking speeds, a long duration cam will relieve some of the combustion chamber pressure, resulting in a lower than normal reading. The more the duration, the lower the reading. Calculate the reading with the duration of the cam in the engine against the duration of a stock OEM cam. Example: If the compression pressure is 100 psi, multiple 100 by 285 (duration of cam that's in the engine) and then divide the answer by 223 degrees (duration of a stock OEM cam), which gives 128 psi.

How To Prepare an Engine for Wintertime or Long-Term Storage -

1. First of all, prepare a cool, dry place of storage with low humidity to lesson the chance of corrosion and rust.
2. Drain the entire fuel system from the equipment being stored. This includes the carburetor float bowl, fuel pump, fuel line, fuel filter and fuel tank. Leave the hose(s) disconnected so the entire fuel system will totally dry out.
3. If the engine is equipped with an electric or mechanical fuel pump, apply about a teaspoon-full of clean automatic transmission fluid in the pump so the pump diaphragm will remain flexible or rotor vanes will won't stick and to prevent the poppet valves from sticking or becoming corroded.
4. Remove the spark plug, squirt about a teaspoon-full of clean automatic transmission fluid (ATF) into the combustion chamber.
5. Reinstall the spark plug and crank the engine several revolutions to evenly distribute the oil on the cylinder wall, valves, seats and valve stems (guides). (Automatic transmission fluid contains a rust inhibitors so the engine parts won't corrode or rust.)
6. Run the piston up at TDC on the compression stroke. Doing this will prevent the valves from sticking open, and the valve springs won't be under extreme pressure.
7. And that's all that's to it!

How to Tell the Differences Between the 10hp, 12hp, 14hp and 16hp Kohler Engine Blocks -

• The 10hp (model K241 or M10) blocks have a bore of 3.250" and the stroke is 2.875". Some rare 10hp blocks have a casting embossed above the PTO end reading "K301." These have a thicker cylinder wall than ordinary 10hp blocks. All 10hp blocks have an exhaust valve diameter if 1.125" and the intake is 1.375".
• The 12hp (model K301 or M12) blocks have a bore of 3.375' and the stroke is 3.250". There are no other differences between the 10hp and 12hp blocks. The 10hp and 12hp blocks have the same size valves, and all of the external parts will interchange. The 10hp and 12hp engines use a #26 (1.07" throttle bore) carburetor.
• The 14hp (model K321 or M14) blocks have a bore of 3.500' and the stroke is 3.250". There are no other differences between the 10hp, 12hp and 14hp blocks, except in the 14hp, the valves are the same diameter, 1.375". All the external parts will interchange with the 10hp, 12hp and 14hp engines, with the exception of the early style 10hp cylinder head and the carburetor. The 14hp uses either a larger #28 or #30 (1.17" or 1.2" throttle bore) carburetor.
• The 16hp (model K341 or M16) blocks have a bore of 3.750" and the stroke is 3.250". There are no other differences between the 10hp, 12hp, 14hp and 16hp blocks, except the valves are the same diameter, 1.375" and the 16hp have 10 cylinder head bolts. The 16hp also uses a #30 (1.2" throttle bore) carburetor. And all the external parts will interchange with the 10hp, 12hp, 14hp and 16hp engines.

Machine Shop Services - Advertisement: Top of page

If you need professional machine work performed on your engine block, cylinder head, crankshaft and/or connecting rod, or if you need various engine parts, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA | Phone: 1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. More of our parts & services: Engine Rebuild Parts, Machine Shop Services, Engine Rebuilds & Build-up and Exhaust Header Pipe Kits Precision Dynamic Spin-Balancing Service - To balance an engine, I need the crankshaft, piston/rings, pin, clips, connecting rod and bearing inserts. The flywheel is balanced separately. Balance cast crankshaft - $125.00 labor (mallory extra). Balance steel crank - $150.00 and up (mallory extra). Balance flywheel (steel or cast) - $50.00 labor. Engine Block - Bore cylinder to fit next oversize piston (OEM engine block): $50.00 labor per cylinder. Bore cylinder to fit aftermarket piston (new aftermarket [Kohler] block): $120.00 labor. Clearance bottom cylinder bore for stroker crankshaft: $75.00 labor. Bore cam pin holes to 11/16" (.6875") for installation of needle bearings (OEM or aftermarket [Kohler] block): $50.00 labor. Remove welch plug and cut threads for auxiliary crankcase breather (OEM and aftermarket [Kohler] block: $20.00 labor. Clean block: $7.00 labor. Drill and tap two 5/16"-18 holes in exhaust flange (to mount header pipe): $30.00 labor. Drill out broken bolt in exhaust flange and cut new 5/16-18 NC threads (to mount header pipe): $10.00 labor each. Resurface exhaust mounting flange (to insure sealing of header pipe flange): $10.00 labor. Drill 7/8" center hole and two outer 1/4" bolt holes in 10-16hp Kohler blocks to mount mechanical fuel pump. $50.00 labor. Convert wide base block to narrow base. (Cut off flanges and grind remaining metal even with block.) $75.00 labor. Convert wide base block to narrow base. (Cut off flanges, grind remaining metal even with block and cut threads in oil pan mounting holes.) $85.00 labor. Convert wide base block to narrow base. (Cut off flanges, weld in steel stock to fill in oil fill holes and grind remaining metal even with block.) $100.00 labor. Convert wide base block to narrow base. (Cut off flanges, weld in steel stock to fill in oil fill holes, grind remaining metal even with block and cut threads in oil pan mounting holes. $110.00 labor. Valve Train Related - Grind used valve to OEM angle: $3.00 each. Grind [45°] intake valve at 30° angle: $5.00 each. Grind seat to OEM angle or 30° angle: $3.00 each. Perform valve job to OEM specs (grind two valve faces and seats), install valves in OEM [Kohler] block and set clearances: $25.00 labor, plus return shipping & handling. Regrind and rework two stock valves and seats in OEM [Kohler] block for improved airflow: $40.00 labor, plus return shipping & handling. Price includes grinding the exhaust valve & seat at 45°/46° angles, intake valve and seat at 30°/31° angles respectively and undercutting both valve heads. Install oversize valves (OEM [Kohler] block): $150.00 labor, plus return shipping & handling. Price does not include any parts. Install oversize valves (aftermarket [Kohler] block with small uncut valve pockets): $150.00 labor, plus return shipping & handling. Price does not include any parts. Port/polish intake and exhaust runners (OEM and aftermarket [Kohler] block with large ports): $75.00 labor, plus return shipping & handling. Port/polish intake and exhaust runners (aftermarket [Kohler] block with small ports): $200.00 labor, plus return shipping & handling. Install 1-3/8" exhaust valve in 10, 12 and older 14hp OEM Kohler block: $50.00 labor, plus return shipping & handling. Install oversize valves, and port/polish intake and exhaust runners (OEM [Kohler] block): $175.00 labor, plus return shipping & handling. Install oversize valves, and port/polish intake and exhaust runners (aftermarket [Kohler] block): $300.00 labor, plus return shipping & handling. Install OEM-type [centered] replacement cast iron valve guides in OEM Kohler block: $15.00 each. Install offset valve guides in OEM Kohler block: $45.00. Includes labor and two steel guides with thin-wall bronze sleeves. Plus return shipping & handling. Install thin-wall bronze sleeves in valve guides in Kohler and other makes of engines with no removable valve guides. $8.00 each. (Bronze valve guide sleeves are an alternative to replacing the entire guide in Kohler engines. Bronze also last longer than Kohler's cast iron guides because bronze retains more oil for better lubrication of the valve stem.) Cylinder Head Work - Resurface air-cooled small engine cylinder head to remove warpage: $3.00 each, plus return shipping & handling. Mill cylinder head approximately .050". Remove raised gasket mating surface from head to increase compression ratio for the 10-16hp flathead, K-series or Magnum single cylinder engines only. $25.00 labor each, plus return shipping & handling. Click photo to the right for a larger view. NOTE: Seal the head gasket or when the head is fastened directly to the block with Permatex® Ultra Copper® Maximum Temperature RTV Silicone Gasket Maker or Copper SPRAY-A-GASKET Hi Temp Adhesive Sealant to prevent a blown or leaking head gasket. Because engine heat has very little effect on silicone sealant. Repair stripped spark plug threads. No need to purchase another cylinder head. $5.00 - $20.00 each (depending on size of hole and type of head) for parts and labor, plus return shipping & handling. Mill out exhaust valve cavity in LP and 2nd generation cylinder head to clear the larger 1-3/8" exhaust valve. $25.00 labor, plus return shipping & handling. Repair loose valve seat in the OHV 18hp K361 Kohler or Tecumseh OHV engines. (Install oversize o.d. valve seat so the OEM valve can still be reused.): $40.00 each for parts and labor, plus return shipping & handling. Install oversize o.d. valve guide in the same heads above (so the OEM valve can still be reused.): $20.00 each for parts and labor, plus return shipping & handling. Crankshaft Repairs- Regrind small engine crankshaft journal (crank pin): $50.00 per journal, plus return shipping & handling. Note: Kohler crankshafts can be reground to .030" undersize and still be safe to use with matching undersized bearing inserts installed in the connecting rod. And all crankshafts, rather if they're automotive or small engine, are checked for straightness before grinding. If they're bent or twisted, sometimes they can be straightened. I also do offset crankshaft grinding to increase the length of the stroke at no extra charge. On the 7hp and 8hp Kohler and other makes and models of engines when an undersize connecting rod or bearing inserts isn't available, if the crankshaft is worn beyond .010" and needs to be reground again, the journal can be reground to wherever it "cleans up" or is true again, and then the connecting rod can be resized so it'll fit the smaller undersize journal. To fit the rod to the smaller diameter crank journal, I remove metal from the mating end of the rod cap, then I fasten the cap to the rod. The big hole in the rod is now oblong or "egg shaped." Then I resize the hole until it's .002" larger than the diameter of the crank journal. This reshapes the hole into a perfect circle again, only smaller in diameter. This can only be performed on a rod with a good bearing surface. It cannot be done on a burnt or heavily scored connecting rod. This works very well and it lasts as long as an ordinary STD rod and crank journal. The cost for doing this is $75.00 labor, plus return shipping & handling. If you're interested, I will need your crankshaft and connecting rod. Repair broken off stud in crankshaft on flywheel end: $30.00 labor, plus return shipping & handling. I drill and cut threads for a hardened 3/8" or 5/8" diameter bolt in the end of the crankshaft to secure the flywheel. Drill hole and cut 7/16-20 NF threads in the PTO end of the crankshaft for a retaining bolt and flat washer. $20.00.

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Miller's Engine Refreshing, Rebuilding, and Build-up Service - (updated 4/22/12)

If you need your engine rebuilt or built up for pulling competitively or so it'll produce more power and torque, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA | Phone: 1-573-875-4033. Please call Monday-Friday, 9am to 5pm, Central time. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. You can also contact us through Yahoo! Messenger: Find us here: Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. More of our parts & services: Engine Rebuild Parts, Machine Shop Services, Engine Rebuilds & Build-up and Exhaust Header Pipe Kits

Bare Kohler K-series Engine Blocks (when available) - Top of page 6¼hp, 7hp and 8hp engine block. (K141, K161 & K181; with 2-15/16" bore) $40.00 each, plus shipping & handling. 10hp (K241) engine block. $65.00 each, plus shipping & handling. 10hp (K241) engine block with 10hp bore and K301 embossed on the PTO end. (Extra thick cylinder wall.). $200.00 each, plus shipping & handling. 12hp (K301) engine block. $125.00 each, plus shipping & handling. 14hp (K321) engine block. $150.00 each, plus shipping & handling. 16hp (K341 - 12 fin) engine block. $250.00 each, plus shipping & handling. 16hp (K341 - 13 fin) engine block. $400.00 each, plus shipping & handling. Packaged shipping weight for each block is 25 lbs. NOTE: There are many variations in the 10, 12, 14 and 16hp Kohler blocks: Some blocks have a wide base (flanges) and some have a narrow base. The very early 10hp blocks have no indention for installing an upper mount gear starter. Also, some of these blocks with flanges (for the wide oil pan) have no holes drilled for converting to a narrow base oil pan. (But the holes can be drilled and tapped.). Some have the oil dipstick tube hole next to the cylinder, while others have no hole there. The hole is either drilled or threaded. Some blocks have provisions for a starter-side mounted oil dipstick tube, and some don't. Some blocks come with balance gears and some don't. Some have a plug where balance gear stub shafts can be installed, and some have no holes drilled for the stub shafts. Some blocks have two threaded holes for mounting an exhaust pipe flange and provisions to mount a mechanical fuel pump, and some don't have these. The threaded holes on the PTO end of the block can have different bolt patterns. A 12 fin 16hp block works great for the Stock, Stock Altered and Missouri Super Stock classes, and the 13 fin 16hp block works better for the 50+ cube class because it has a thicker cylinder wall. Other than these things, everything else on the blocks is pretty much the same.

Engine Rebuilding Service - I rebuild engines from ordinary stock up to 4,000 rpm governored pulling engines. I can rebuild your engine however you want. Just tell me know how you're going to use your tractor or equipment and I'll build your engine to suit your needs. If you wish to have me rebuild or build-up your engine, I'll need a list of what you want done to your engine or a copy of your club's pulling rules regarding the engine requirements before I can give you an estimate on the cost. I'll build your engine to the limit according to the rules, not less than what the rules allow. I also rebuild ordinary lawn & garden equipment engines too, such as cast iron and aluminum block single- and twin-cylinder flathead, OHV and v-twin Briggs & Stratton, Kohler, Tecumseh and 2-cycle LawnBoy. Whenever I rebuild or build-up an engine, and if you wish to do so, I do whatever it takes so it'll produce the factory-rated horsepower or the maximum horsepower and torque, and last a long time. I go beyond what the repair manual says to do. I can get all the parts needed, too. I can build your engine so it'll be legal for the class you plan to pull in. And with my engine rebuilds and build-ups, you may not always win, but you'll look good trying! FYI - Being I'm the only person to read and respond to all my customer's emails (about 20 or so a day), take my customer's phone calls (about 20-30 on a nice day), with customers stopping by my shop, repair and rebuild my customer's parts and engines in my shop, order parts from my suppliers, package and mail my customer's parts at my local Post Office, etc., it may take me several months, possibly up to 5 months to rebuild an engine. So please keep this in mind if you decide to have me rebuild your engine. All pulling engine builds are strictly confidential. This means your pulling competition will not know what goes into your engine!

Below are details and prices to rebuild your engine -

Briggs & Stratton 3hp to 5hp flathead aluminum block engine (horizontal or vertical shaft) rebuild to OEM factory specifications @ 3,600 governed rpms (for general yard work only) Your engine: $85 - $125 (depending on size of engine and extent of wear), includes our parts and labor, return shipping extra. Parts and labor includes new rings, professional valve job, clean and rebuild carburetor, new gaskets, oil seals and whatever else it may need. Briggs & Stratton 7hp through 12.5hp single cylinder flathead aluminum block engine (horizontal or vertical shaft) rebuild to OEM factory specifications @ 3,600 governed rpms (for general yard work only) Your engine: $450±, includes our parts and labor, return shipping extra. Parts and labor includes new rings, professional valve job, clean and rebuild carburetor, new gaskets, oil seals and whatever else it may need. Briggs & Stratton 16, 18 & 20hp flathead/opposed twin cylinder aluminum block engine (horizontal or vertical shaft) rebuild to OEM factory specifications @ 3,600 governed rpms (for general yard work or mild competitive pulling): Your engine: $600-$700±, includes our parts and labor, return shipping extra. Parts and labor includes new rings, professional valve job, clean and rebuild carburetor, new gaskets, oil seals and whatever else it may need.

Tecumseh 3hp to 10hp flathead aluminum block engine (horizontal or vertical shaft) rebuild to OEM factory specifications @ 3,600 governed rpms (for general yard work only) Your engine: $75 - $600± (depending on size of engine and extent of wear), includes our parts and labor, return shipping extra. Tecumseh 8hp (VH80/HH80), 10hp (VH100/HH100), 12hp (HH120/OH120), 14hp (OH140), 15hp (OH150), 16hp (OH160) & 18hp (OH180) flathead & OHV cast iron block engines (horizontal & vertical shaft) rebuild to OEM factory specifications @ 3,600 governed rpms (for general yard work only) Your engine: $500 - $800± (depending on size of engine and extent of wear), includes our parts and labor, return shipping extra. Parts and labor includes new rings, professional valve job, clean and rebuild carburetor, new gaskets, oil seals and whatever else it may need.

Lawn-Boy 2-cycle engine (lawn mower models C, D & F) rebuild to OEM factory specifications @ 3,200 governed rpms (for general yard work only) Your engine: $100± (depending on model of engine and extent of wear), includes our parts and labor, return shipping extra. Parts and labor includes new rings and/or piston, clean and rebuild carburetor, new gaskets, oil seals and whatever else it may need.

New lower prices, same quality and performance. FYI - Being I'm the only person to read and respond to all my customer's emails (about 20 or so a day), take my customer's phone calls (about 20-30 on a nice day), with customers stopping by my shop, repair and rebuild my customer's parts and engines in my shop, order parts from my suppliers, package and mail my customer's parts at my local Post Office, etc., it may take me several months, possibly up to 5 months to rebuild your engine. So please keep this in mind if you decide to have me rebuild your engine. If you wish to have me rebuild or build-up your engine, I'll need a list of what you want done to your engine or a copy of your club's pulling rules regarding the engine requirements before I can give you an estimate on the cost. I'll build your engine to the limit according to the rules, not less than what the rules allow. Kohler 4hp, 7hp and 8hp flathead cast iron block engine rebuild to OEM factory specifications @ 4,000 governed rpm (for general yard work or mild competitive pulling) Your engine: $400±, includes our parts and labor, return shipping extra. Parts and labor includes: bore cylinder (if needed); install new piston/rings; regrind crank journal (if needed); resize connecting rod or install new .010" rod (if needed); regrind valves/seats; rebuild carburetor; resurface cylinder head; install new gaskets/oil seals, tune-up kit and refurbish gear starter. Kohler 10hp, 12hp or 14hp cast iron flathead block engine rebuild to OEM factory specifications @ up to 4,000 governed rpm (for general yard work or mild competitive pulling) Your engine: $500±, includes our parts and labor, return shipping extra. Parts and labor includes: bore cylinder (if needed); install new piston/rings; regrind crank journal (if needed); fit connecting rod w/bearing inserts (if needed); regrind valves/seats; rebuild carburetor; resurface cylinder head; install new gaskets/oil seals, tune-up kit and refurbish gear starter. If engine has a broken connecting rod, and internal damage has resulted, the price will be slightly higher for additional parts & labor. Kohler 10hp, 12hp or 14hp cast iron flathead block Stock-Appearing engine build to the max @ up to 4,000 rpm (for heavy yard work or competitive pulling) Your engine: $900±, includes our parts and labor, return shipping extra. Parts and labor includes: rework stock valves; install our reground high torque, low rpm cast camshaft; port/polish; rework #26 carburetor; mill OEM cylinder head; regrind crank journal (if needed); fit stock connecting rod w/bearing inserts; stock piston assembly; stock flywheel w/3/4 fins removed (dynamically precision spin-balanced), new tune-up kit and refurbish gear starter. If engine has a broken connecting rod, and internal damage has resulted, the price will be slightly higher for additional parts & labor. Kohler 16hp cast iron flathead block engine rebuild to OEM factory specifications @ up to 4,000 governed rpm (for general yard work or mild competitive pulling) Your engine: $600±, includes our parts and labor, return shipping extra. Parts and labor includes: bore cylinder (if needed); install new piston/rings; regrind crank journal (if needed); fit connecting rod w/bearing inserts (if needed); regrind valves/seats; rebuild carburetor; resurface cylinder head; install new gaskets/oil seals, tune-up kit and refurbish gear starter. If engine has a broken connecting rod, and internal damage has resulted, the price will be slightly higher for additional parts & labor. Kohler 16hp (K341) cast iron flathead block Stock-Appearing engine build to the max @ up to 4,000± rpm (for heavy yard work or competitive pulling) Your engine: $900.00±, includes our parts and labor, return shipping extra. Parts and labor includes: rework stock valves; install our reground high torque, low rpm cast camshaft; port/polish; rework #26 carburetor; mill OEM cylinder head; regrind crank journal (if needed); fit stock connecting rod w/bearing inserts; stock piston assembly; stock flywheel w/3/4 fins removed (dynamically precision spin-balanced), new tune-up kit and refurbish gear starter. If engine has a broken connecting rod, and internal damage has resulted, the price will be higher for additional parts & labor. Kohler 18hp (K361) cast iron single cylinder OHV block engine. Your engine - rebuild to OEM factory specifications @ up to 4,000 governed rpm (for general yard work or mild competitive pulling): $800±, includes our parts and labor, return shipping extra. Parts and labor includes: bore cylinder (if needed); install new piston/rings; fit connecting rod w/bearing inserts (if needed); regrind valves/seats; rebuild carburetor; resurface cylinder head; install new gaskets/oil seals, tune-up kit and refurbish gear starter. If engine has a broken connecting rod, and internal damage has resulted, the price will be higher for additional parts & labor. Kohler 17hp, 19hp K-series & 18hp, 20hp M18 & M20 Magnum opposed twin cylinder flathead engines. Rebuild to OEM factory specifications @ up to 4,000 governed rpm (for general yard work or mild competitive pulling). Your engine - $600±, includes our parts and labor, return shipping extra. Parts and labor includes: install new rings; regrind valves/seats; rebuild carburetor; resurface cylinder heads; install new gaskets/oil seals, tune-up kit and refurbish gear starter. If engine has a broken connecting rod, and internal damage has resulted, the price will be higher for additional parts & labor. Kohler 25hp V-Twin engine. Rebuild to OEM factory specifications @ up to 4,000 governed rpm (for general yard work or mild competitive pulling). Your engine - $700±, includes our parts and labor, return shipping extra. Parts and labor includes: install new rings; regrind valves/seats; rebuild carburetor; resurface cylinder heads; install new gaskets/oil seals, tune-up kit and refurbish gear starter. If engine has a broken connecting rod, and internal damage has resulted, the price will be higher for additional parts & labor.

Competitive Pulling Engine Refreshing Service Ê A typical pulling engine will last an average of 25 pulls or 3 years of use. After that, it may start to lose power when under load and puff smoke out the crankcase breather vent and/or out the exhaust. When this happens, it's time for a refreshing job. This service is for engines that have been previously rebuild or built for pulling, and needs the basic parts to revive the power. It is not a complete rebuild. Top of page Refresh Stock 10-16hp Kohler pulling engine. Includes new rings, lap valves, adjust valve clearance, new rod bearing, clean or rebuild carburetor, new up-to-date Lakota, MWSC or Vogel torque camshaft and new gaskets. $200.00 labor. Parts are extra charge. Refresh Stock-Altered 12-16hp Kohler engine. Includes new rings, lap valves, adjust valve clearance, new rod bearing, clean or rebuild carburetor, new up-to-date Lakota, MWSC or Vogel camshaft and new gaskets. $300.00 labor. Parts are extra charge. Add $200.00 labor to machine the valve cavities deeper in billet cylinder head if a new camshaft with more lift will be installed. Refresh NQS 30 c.i. or Missouri Super-Stock 16hp Kohler engine. Includes new rings, lap valves, adjust valve clearance, new rod bearing, clean or rebuild carburetor, new up-to-date Lakota, MWSC or Vogel camshaft, new gaskets. $400.00 labor. Parts are extra charge. Add $200.00 labor to machine the valve cavities deeper in billet cylinder head if a new camshaft with more lift will be installed. Refresh 50.5 c.i. 16hp Kohler engine. Includes new rings, lap valves, adjust valve clearance, new rod bearing, new up-to-date Lakota, MWSC or Vogel camshaft, clean or rebuild carburetor, new gaskets and oil seals. $500.00 labor. Parts are extra charge. Add $200.00 labor to machine the valve cavities deeper in billet cylinder head if a new camshaft with more lift will be installed.

Competitive Stock-Class 4,000 RPM Pulling Engines Ê Top of page "Built to the max" 10hp (K241), 12hp (K301), 14hp (K321) or 16hp (K341) Kohler engines built by Brian Miller. These engines have a 5,000 rpm limit with an operating cast iron governor gear; high torque camshaft; high-flow reworked stock size valves; #26 Kohler carburetor bored to 1", reworked & set up for gas; enlarged ports & polished; 2nd generation cylinder head milled .050"; connecting rod bored .020" offset for piston pop out with quality bearing inserts; 9-1/2" cast flywheel with majority of fins removed & dynamically precision spin-balanced; upper mount gear starter, header pipe and conventional Kohler point ignition system. These are very powerful engines! These engines are for Cub Cadet garden tractors, and built and designed for competitive pulling in the Stock classes only, not yard work. No charging systems. New lower prices, same quality and performance. 10hp (Produces 17hp and 22 ft. lbs. of torque @ 4,000 rpm.) $1,000.00 12hp (Produces 22hp and 28 ft. lbs. of torque @ 4,000 rpm.) $1,200.00 14hp (Produces 25hp and 32 ft. lbs. of torque @ 4,000 rpm.) $1,400.00 16hp (Produces 27hp and 36 ft. lbs. of torque @ 4,000 rpm.) $1,600.00 Shipping and crating not included in prices above.

NOTES:

• A general stock engine rebuild includes: completely disassemble entire engine, clean and inspect all parts, bore (if it needs it) or deglaze cylinder, install new piston/rings/pin/clips assembly, regrind crankshaft journal (if it needs it), install new undersize (.010") connecting rod or bore rod for undersize bearing inserts (.020" or .030"; if it needs it), grind valves and seats, install new gaskets with silicone sealer to lesson oil leaks, install new ignition tune up components, resurface cylinder head, clean and rebuild carburetor, clean commutator and lubricate bushings in gear starter and whatever else the engine may need so it'll run well and last a long time.
• The engines I sell are turn key engines. I build all engines according to the customer's personal preferences for non-pulling purposes or to the customer's pulling club's sanctioning rules. "Build to the max" means engine will produce all the power possible and still remain stock-appearing externally. All of the above will be performed in addition to the mild performance modifications.
• ± means more or less. This means if your engine needs minimal labor and/or machining, the price will be slightly less. But if it needs more than usual labor and/or machining, the price will be slightly higher. However, if it has sustained major internal damage or if it needs additional parts, extensive machine work and more labor, then the price will be even higher. And being I can't see your engine before you bring or send it to us, I can't honestly give an exact quote beforehand. But we'll treat you right and we'll try to keep the costs down as much as possible and still build you a quality engine so it'll start easy, produce full power and last a long time. The ± also depends on your personal preferences, parts needed and/or your pulling club's sanctioning rules. Also, if you wish to furnish some or all of the parts yourself, the price will be substantially lower.
• When sending or bringing an engine to me, I don't need everything on it. Only the things that can wear and need rebuilding or refurbishing, such as the gear starter, cylinder head, crankcase breather assembly, fuel pump and carburetor. I need the oil pan on it too, to prevent dirt and dust from entering the crankcase. If you can't pull the flywheel, that'll be fine. I can remove it. A 50% deposit may be required on some engine rebuilds.
• And all rebuilt engines returned (shipped) to the customer are wrapped with plastic to prevent dust and dirt contamination and come with a 90 day workmanship warranty from date of pickup or delivery. For a newly rebuilt engine, SAE 30 weight oil should be used for break-in so the parts will form a wear pattern, then after 2 hours of use, switch to 10W30 (for stock engines) or 20W50 (for high performance engines) full synthetic oil.

If you decide to ship your engine to me, please enclose it in a sturdy wooden crate or cardboard box with cushioning surrounding the engine, and then fasten or strap it securely onto a wooden pallet. Do not use a cardboard box alone! To build a crate, start with 2" x 2" frame work with a skid pallet on the bottom (so a forklift can pick it up without damage), fasten the oil pan of the engine to the bottom of the crate (pallet), use either 1/4" plywood or paneling to cover the crate, place some heavy pieces of Styrofoam or heavy cardboard around and above the engine to help cushion it during transport, and fasten everything on and in the crate with sheet rock screws. Or if you bring an engine to us in person, sit it in an old tire to keep it from moving around during transportation. And please let us know first so I can expect your arrival. It'll be best to have everything on the engine that can wear so I can repair them too, and make the necessary adjustments.

To ship your engine to us, first off, do not use the US Mail Service, UPS or FedEx Express! We and our customers have had too many problems with them in the past. They wouldn't even make good on the insurance either. Their gorillas (employees) are trained in handling lightweight packages (weighing up to 70 lb.) and the heavier items tend to get damaged with their kind of handling. They are very hard on heavy packages when they handle them. The packages are placed on conveyor-belt systems and they seem to always drop the heavy ones off of the elevated conveyors, which usually destroys whatever is inside them.

If you decide to ship your engine to me, please crate it well. We're authorized FedEx Ground (for anything up to 150 lbs.) and FedEx Freight (for anything over 150 lbs.) shippers because they've been proven to be the lowest cost, most gentle and reliable shipping companies. Here's a great web site that calculates freight charges. Go here: http://www.shipgooder.com/ and type in your zip code, our zip code (65203) and the crated weight of a typical complete 10-16hp Kohler engine (145 lb.). Contact your local FedEx Ground for more details. Or you can use a major trucking company with a good reputation for shipping heavy, fragile objects. Look in the Yellow Pages and ask around. The reason we say this is because we once returned a rebuilt engine that was crated very well to a customer using a well-known shipping company, and it was almost destroyed in shipping when he received it. You'll have better success with shippers such as FedEx Ground, FedEx Freight, Roadway, etc. Freight company employees are trained in handling heavy packages plus they use tow motors to move the freight around, not like UPS or FedEx Express with their uncaring "gorillas" unloading and loading the trucks. The approximate shipping weight of a crated 7 and 8hp Kohler engine is 100 lbs. And 10-16hp single cylinder cast iron Kohler engine is 145 lbs.

I don't build high-performance V-twins and I know very little about how to improve the performance of them because no one here in Missouri pulls them. The only contacts I have concerning V-twin engine builders and high-performance parts are listed below. Contact them and perhaps they can answer your questions.

• Al Hodge Performance V-Twins. He modifies the Briggs & Stratton Vanguard V-twins for all types of racing and performance applications. Output ranges from 25 to 42hp. Modified engine weight is around 80 lbs. He supplies engines for some of the fastest Cushmans in the National Champion lawnmower racers, tractor pullers, Class Champion scale sprint cars, ATV's, hunting boat upgrades, etc. All of his engines are non-governed and include solenoid shift, high torque starters. Sorry, he doesn't have a manual or any printed literature....he offers cams, billet rods, high compression pistons, mega-valve machine ported heads, titanium valves, rev-kits, roller rockers, billet push rods, billet rocker covers, stroker kits, etc. Give Al a call @ 704-291-7825 Monday thru Friday 10:00 am until 4:00 pm EST. E-mail: pki@trellis.net
• R.P.M. - Rader Performance Motors When Performance Counts, Count on Rader Performance Motors! Services Include: Complete Engine Building - Stock, Stock-Altered and Kohler V-Twins Custom Flow Bench Water Brake Dyno Tuning = Maximum Horsepower Dyno Tested, Track Proven Performance Contact: Mark Rader | Phone: (740) 927-3312 | E-mail: rpmark@sprintmail.com | Web site: http://www.geocities.com/ipld
• Frank Edwards of Galax, VA. Kawasaki water cooled V-Twin garden tractor high performance. Selling performance parts and building complete pulling engines. Call for details. 276-236-5305. E-mail: sdrawde@ntelos.net
• Lakota Racing ( http://www.lakotaracing.com/ )
• Midwest Super Cub ( http://www.midwestsupercub.net/ )
• Performance V-Twins ( http://www.performancevtwins.com/ )

Kohler K-Series - Single Cylinder Engine Specifications and Tolerances
All dimensions in inches. (Click here to print out the below.)

Model (Horsepower @ 3,600 rpm)				K90 / K91 (4hp)	K141 (6¼hp) K161 (7hp)	K181 (8hp)	K241 (10hp)	K301 (12hp)	K321 (14hp)	K341 (16hp)	K361 (18hp) (Over Head Valve)
General	Bore x Stroke			2.375" x 2.000"	2.875" (early) 2.938" (late) x 2.500"	2.938" x 2.750"	3.251" x 2.875"	3.375" x 3.250"	3.500" x 3.250"	3.750" x 3.250"	3.750" x 3.250"
	Cubic Inch Displacement			8.86	16.22 / 16.95	18.64	23.85	29.07	31.27	35.90	35.90
	Compression Ratio			?	?	?	7.1:1, 5.4:1 or 5:1 (See note 8)	8.6:1, 6.6:1 or 6.1:1 (See note 8)	6.6:1, 7:1 or 9:1 (See note 8)	7.4:1	9.2:1
	Operating RPM (maximum)			4,000	3,600	3,600	3,600	3,600	3,600	3,600	3,600
Balance Gear	Shaft O.D.	New		-	-	-	.4998" (min.) .5001" (max.)	.4998" (min.) .5001" (max.)	.4998" (min.) .5001" (max.)	.4998" (min.) .5001" (max.)	.4998" (min.) .5001" (max.)
		Wear Limit (maximum)		-	-	-	.4996"	.4996"	.4996"	.4996"	.4996"
	End Play			-	-	-	.002" (min.) .010" (max.)	.002" (min.) .010" (maz.)	.002" (min.) .010" (max.)	.002" (min.) .010" (max.)	.002" (min.) .010" (max.)
Camshaft	End Play			.005" (min.) .020" (max.)	.005" (min.) .010" (max.)	.005" (min.) .010" (max.)	.005" (min.) .010" (max.)	.005" (min.) .010" (max.)	.005" (min.) .010" (max.)	.005" (min.) .010" (max.)	.005" (min.) .010" (max.)
Connecting Rod	Running Clearance		Big End Diameter (maximum)	.938" (STD)	1.1875" (STD)	1.1875" (STD)	1.5015" (STD)	1.5015" (STD)	1.5015" (STD)	1.5015" (STD)	1.5015" (STD)
			Rod to Crankpin	.001" (min.) .0025" (max.)	.001" (min.) .002" (max.)	.001" (min.) .002" (max.)	.001" (min.) .002" (max.)	.001" (min.) .002" (max.)	.001" (min.) .002" (max.)	.001" (min.) .002" (max.)	.001" (min.) .002" (max.)
			Rod to Crankpin Wear Limit (maximum)	.003"	.0025"	.0025"	.0025"	.0025"	.0025"	.0025"	.0025"
			Rod to Piston Pin	.0007" (mim.) .0008" (max.)	.0006" (min.) .0011" (max.)	.0006" (min.) .0011" (max.)	.0003" (min.) .0008" (max.)	.0003" (min.) .0008" (max.)	.0003" (min.) .0008" (max.)	.0003" (min.) .0008" (max.)	.0003" (min.) .0008" (max.)
	Small End I.D.			.5630" (min.) .5633" (max.)	.6255" (min.) .6258" (max.)	.6255" (min.) .6258" (max.)	.8596" (min.) .8599" (max.)	.8757" (min.) .8760" (max.)	.8757" (min.) .8760" (max.)	.8757" (min.) .8760" (max.)	.8757" (min.) .8760" (max.)
Crankshaft	Main PTO and Flywheel End O.D.		New (max.)	.9844"	1.1814"	1.1814"	1.5749"	1.5749"	1.5749"	1.5749"	1.5749"
			Wear Limit (maximum)	.9841"	1.1811"	1.1811"	1.5745"	1.5745"	1.5745"	1.5745"	1.5745"
	Crankpin	New		.9355" (std) .9360" (max.)	1.1855" (std) 1.1860" (max.)	1.1855" (std) 1.1860" (max.)	1.4995" (std) 1.5000" (max.)	1.4995" (std) 1.5000" (max.)	1.4995" (std) 1.5000" (max.)	1.4995" (std) 1.5000" (max.)	1.4995" (std) 1.5000" (max.)
		Wear Limit (maximum)		.9350"	1.1850"	1.1850"	1.4990"	1.4990"	1.4990"	1.4990"	1.4990"
		Out of Round (maximum)		.0005"	.0005"	.0005"	.0005"	.0005"	.0005"	.0005"	.0005"
		Taper (max.)		.001"	.001"	.001"	.001"	.001"	.001"	.001"	.001"
	End Play			.004" (min.) .023" (max.)	.002" (min.) .023" (max.)	.002" (min.) .023" (max.)	.003" (min.) .020" (max.)	.003" (min.) .020" (max.)	.003" (min.) .020" (max.)	.003" (min.) .020" (max.)	.003" (min.) .020" (max.)
Cylinder Bore	Inside Diameter		New	2.3745" (std) 2.3755" (max.)	2.9370" (std) 2.9380" (maz.)	2.9370" (std) 2.9380" (maz.)	3.2505" (std) 3.2515" (max.)	3.3745" (std) 3.3755" (max.)	3.4995" (std) 3.5005" (max.)	3.7495" (std) 3.7505" (max.)	3.7495" (std) 3.7505" (max.)
			Maximum Wear Limit	2.378"	2.941"	2.941"	3.254"	3.378"	3.503"	3.753"	3.753"
	Maximum Out of Round			.003"	.003"	.003"	.003"	.003"	.003"	.003"	.003"
	Maximum Taper			.003"	.003"	.003"	.002"	.002"	.002"	.002"	.002"
Cylinder Head	Maximum Out of Flatness			.003"	.003"	.003"	.003"	.003"	.003"	.003"	.003"
Ignition	Spark Plug - Type and Gap		Type (See note 2)	RCJ-8	RCJ-8	RCJ-8	RH-10	RH-10	RH-10	RH-10	RH-10
			Battery	.035"	.035"	.035"	.035"	.035"	.035"	.035"	.035"
			Magneto	.025"	.025"	.025"	.025"	.025"	.025"	.025"	.025"
			LP/Propane	.018"	.018"	.018"	.018"	.018"	.018"	.018"	.018"
	Nominal Point Gap/Mark on Flywheel/Degrees BTDC Setting			.020" / S / 20º	.020" / S / 20º	..020" / S / 20º	.020" / S / 20º	.020" / S / 20º	.020" / S / 20º	.020" / S / 20º	.020" / S / 20º
Model (Horsepower)				K90 / K91 (4hp)	K141 (6¼hp) K161 (7hp)	K181 (8hp)	K241 (10hp)	K301 (12hp)	K321 (14hp)	K341 (16hp)	K361 (18hp) (Over Head Valve)
All Pistons	Service Replacement Sizes			ß .003" - .010" - .020" - .030" à
	Thrust Face O.D. (See note 3)		New	2.371"/2.369"	2.9297"/2.9281"	2.9297"/2.9281"	3.2432"/3.2413"	3.368"/3.365"	3.4941"/3.4925"	3.7425"/3.7410"	3.7425"/3.7410"
			Maximum Wear Limits	2.366"	2.925"	2.925"	3.238"	3.363"	3.491"	3.738"	3.738"
	Thrust Face to Bore Clearance (max.) (1)			.0035"/.006"	.007"/.010"	.007"/.010"	.007"/.010"	.007"/.010"	.007"/.010"	.007"/.010"	.007"/.010"
	Ring End Gap		New Bore	.007"/.017"	.007"/.017"	.007"/.017"	.010"/.020"	.010"/.020"	.010"/.020"	.010"/.020"	.010"/.020"
			Used Bore (Maximum)	.027"	.027"	.027"	.030"	.030"	.030"	.030"	.030"
	Maximum Ring Side Clearance			.006"	.006"	.006"	.006"	.006"	.006"	.006"	.006"
	Thrust Face O.D. (See note 5)		New	-	-	-	-	-	-	3.7465"/3.7455"	3.7465"/3.7455"
			Maximum Wear Limits	-	-	-	-	-	-	3.744	3.744
	Thrust Face to Bore Clearance (max.) (See note 1)			-	-	-	-	-	-	.0030"/.0050"	.0030"/.0050"
	Ring End Gap		New Bore (See note 6)	-	-	-	-	-	-	.010"/.020"	.010"/.020"
			Used Bore (Maximum) (See note 6)	-	-	-	-	-	-	.030"	.030"
	Maximum Ring Side Clearance			-	-	-	-	-	-	.004"	.004"
	Thrust Face O.D. (See note 5)		New / Used	-	-	2.9329" (max.) 2.9336" (min.)	-	3.3700" (max.) 3.3693" (min.)	3.4945" (/3.4938"	3.7433"/3.7426"	3.7433"/3.7426"
			Maximum Wear Limits	-	-	2.931"	-	3.367"	3.492"	3.7406"	3.7406"
	Thrust Face to Bore Clearance (max.) (See note 1)			-	-	.0034" (max.) .0051" (min.)	-	.0045" (max.) .0062" (min.)	.0050" (max.) .0067" (min.)	.0062" (max.) .0079" (min.)	.0062" (max.) .0079" (min.)
	Ring End Gap		New Bore (See note 6)	-	-	.010"/.023"	-	.010"/.020"	.010"/.020"	.013"/.025"	.013"/.025"
			Used Bore (Maximum) (See note 6)	-	-	.032"	-	.030"	.030"	.033"	.033"
	Maximum Ring Side Clearance			-	-	.006"	-	.006"	.006"	.004"	.004"
	Piston Pin Outside Diameter			.5623" (min.) .5625" (max.)	.6247" (used .6249" (max.)	.6247" (min.) .6249" (max.)	.8591" (min.) .8593" (max.)	.8752" (min.) .8754" (max.)	.8752" (min.) .8754" (max.)	.8752" (min.) .8754" (max.)	.8752" (min.) .8754" (max.)
Model (Horsepower)				K90 / K91 (4hp)	K141 (6¼hp) K161 (7hp)	K181 (8hp)	K241 (10hp)	K301 (12hp)	K321 (14hp)	K341 (16hp)	K361 (18hp) (Over Head Valve)
Valves	Valve Head Diameter			?	1-3/8" intake 1-1/8" exhaust	1-3/8" intake 1-1/8" exhaust	1-3/8" intake 1-1/8" exhaust	1-3/8" intake 1-1/8" exhaust	1-3/8" intake 1-1/8" (early)/ 1-3/8" (late) exhaust	1.3/8" intake 1-3/8" exhaust	1.3/8" intake 1-3/8" exhaust
	Guide Reamer Size			.250"	.3125"	.3125"	.3125"	.3125"	.3125"	.3125"	.3125"
	Tappet Clearance (Cold)		Intake	.005" (min.) .009" (max.)	.006" (min.) .008" (max.)	.006" (min.) .008" (max.)	.008" (min.) .010" (max.)	.008" (min.) .010" (max.)	.008" (min.) .010" (max.)	.008" (min.) .010" (max.) (See note 4)	.008" (min.) .010" (max.) (See note 4)
			Exhaust	.011" (min.) .015" (max.)	.017" (min.) .019" (max.)	.017" (min.) .019" (max.)	.017" (min.) .019" (max.)	.017" (min.) .019" (max.)	.017" (min.) .019" (max.)	.017" (min.) .019" (max.)	.017" (min.) .019" (max.)
	Minimum Lift (Zero Lash)		Intake	.2035"	.2718"	.2718"	.318"	.318"	.318"	.318"	.318"
			Exhaust	.1768"	.2482"	.2482"	.318"	.318"	.318"	.318"	.318"
	Minimum Stem O.D.		Intake	.2478"	.3103"	.3103"	.3103"	.3103"	.3103"	.3103"	.3103"
			Exhaust	.2458"	.3088"	.3088"	.3074"	.3074"	.3074"	.3074"	.3074"
	Face Angle - Seat Angle -			45º 46º	45º 46º	45º 46º	45º 46º	45º 46º	45º 46º	45º 46º	45º 46º
	Guide I.D. Maximum Wear Limit (See note 1)		Intake	.005"	.005"	.005"	.006"	.006"	.006"	.006"	.006"
			Exhaust	.007"	.007"	.007"	.008"	.008"	.008"	.008"	.008"

Note 1 - Subtract O.D. of inner part from I.D. of outer part. Note 2 - Champion spark plugs or equivalent. Note 3 - Measure just below oil ring groove and at right angles to piston pin. Note 4 - 1,800 RPM generator sets .005/ 007.

Note 5 - Measure 1/2" above the bottom of the piston skirt. Note 6 - Top and center compression rings. Note 7 - Measure just below oil ring groove and at right angles to piston pin. Note 8 - Compression ratio depends on which type of cylinder head is used.

Magnum - Single Cylinder Engine Specifications and Tolerances
All dimensions in inches. (Click here to print out the below.)

Model (Horsepower)			M8 (8)	M10 (10)	M12 (12)	M14 (14)	M16 (16)
General	Bore x Stroke		2.94" x 2.75"	3.25" x 2.88"	3.38" x 3.25"	3.50" x 3.25"	3.75" x 3.25"
	Displacement Cu. In.		18.64	23.85	29.07	31.27	35.90
	Operating RPM (maximum)		3,600	3,600	3,600	3,600	3,600
Balance Gear	Shaft O.D.	New	-	.4998"/.5001"	.4998"/.5001"	.4998"/.5001"	.4998"/.5001"
		Maximum Wear Limit	-	.4996"	.4996"	.4996"	.4996"
	End Play		-	.002"/.010"	.002"/.010"	.002"/.010"	.002"/.010"
Camshaft	End Play		.005"/.010"	.005"/.010"	.005"/.010"	.005"/.010"	.005"/.010"
Connecting Rod	Running Clearance	Maximum Big End Diameter	1.1875" (STD)	1.5015" (STD)	1.5015" (STD)	1.5015" (STD)	1.5015" (STD)
		Rod to Crankpin (max.)	.001"/.002"	.001"/.002"	.001"/.002"	.001"/.002"	.001"/.002"
		Rod to Crankpin - Maximum Wear Limit	.0025"	.0025"	.0025"	.0025"	.0025"
		Rod to Piston Pin (max.)	.0006"/.0011"	.0003"/.0008"	.0003"/.0008"	.0003"/.0008"	.0003"/.0008"
	Small End I.D. (max.)		.6255"/.6258"	.8596"/.8599"	.8757"/.8760"	.8757"/.8760"	.8757"/.8760"
Crankshaft	Main PTO & Flywheel End O.D.	New	1.1811"/1.1814"	1.5745"/1.5749"	1.5745"/1.5749"	1.5745"/1.5749"	1.5745"/1.5749"
		Maximum Wear Limit	1.1811"	1.5745"	1.5745"	1.5745"	1.5745"
	Crankpin	New - O.D.	1.1860"/1.1855"	1.5000"/1.4995"	1.5000"/1.4995"	1.5000"/1.4995"	1.5000"/1.4995"
		Maximum Wear Limit	1.1850"	1.4990"	1.4990"	1.4990"	1.4990"
		Maximum Out of Round	.0005"	.0005"	.0005"	.0005"	.0005"
		Maximum Taper	.001"	.001"	.001"	.001"	.001"
	End Play		.002"/.023"	.003"/.020"	.003"/.020"	.003"/.020"	.003"/.020"
Cylinder Bore	Inside Diameter	New	2.9380"/2.9370"	3.2515"/3.2505"	3.3755"/3.3745"	3.5005"/3.4995"	3.7505"/3.7495"
		Maximum Wear Limit	2.941"	3.254"	3.378"	3.503"	3.753"
	Maximum Out of Round (I.D.)		.005"	.005"	.005"	.005"	.005"
	Maximum Taper (I.D.)		.003"	.002"	.002"	.002"	.002"
Cylinder Head		Maximum Out of Flatness	.003"	.003"	.003"	.003"	.003"
Ignition (Solid State)	Spark Plug	Type (note 2)	RCJ-8	RH-10	RH-10	RH-10	RH-10
		Gap	.025"	.025"	.025"	.025"	.025"
	Module Air Gap		.012"/.016"	.012"/.016"	.012"/.016"	.012"/.016"	.012"/.016"
Model (Horsepower)			M8 (8)	M10 (10)	M12 (12)	M14 (16)	M16 (16)
All Pistons	Service Replacement Sizes		ß .003" - .010" - .020" - .030" à
	Thrust Face O.D. (note3)	New	2.9297"/2.9281	3.2432"/3.2413	3.368"/3.365	3.4941"/3.4925	-
		Maximum Wear Limits	2.925"	3.238"	3.363"	3.491"	-
	Thrust Face to Bore Clearance (max.) (note 1)		.007"/.010"	.007"/.010"	.007"/.010"	.007"/.010"	-
	Ring End Gap	New Bore	.007"/.017"	.010"/020"	.010"/.020"	.010"/.020"	-
		Used Bore (Maximum)	.027"	.030"	.030"	.030"	-
	Maximum Ring Side Clearance		.006"	.006"	.006"	.006"	-
	Thrust Face O.D. (note 4)	New	-	-	-	-	3.7465"/3.7455"
		Maximum Wear Limits	-	-	-	-	3.7435"
	Thrust Face to Bore Clearance (max.) (note 1)		-	-	-	-	.0030"/.0050"
	Ring End Gap	New Bore (note 5)	-	-	-	-	.010"/020"
		Used Bore (Maximum) (note 5)	-	-	-	-	.030
	Maximum Ring side Clearance		-	-	-	-	.004"
	Thrust Face O.D. (note 4)	New	2.9329"/2.9336"	-	3.3700"/3.3693"	3.4945"/3.4938"	3.7433"/3.7426"
		Maximum Wear Limits	2.9312"	-	3.3673"	3.4918"	3.7406"
	Thrust Face to Bore Clearance (max.) (note 1)		.0034"/.0051"	-	.0045"/.0062"	.0050"/0067"	.0062"/.0079"
	Ring End Gap	New Bore (note 5)	.010"/.023"	-	.010"/.020"	.010"/.020"	.013"/.025"
		Used Bore (Maximum) (note 5)	.032"	-	.030"	.030"	.033"
	Maximum Ring Side Clearance		.006	-	.006	.006	.004
Piston Pin	Outside Diameter		.6247" (min.) .6249" (max.)	.8591" (min.) .8593" (max.)	.8752" (min.) .8754" (max.)	.8752" (min.) .8754" (max.)	.8752" (min.) .8754" (max.)
Valves	Valve Head Diameter		1-3/8" intake 1-1/8" exhaust	1-3/8" intake 1-1/8" exhaust	1-3/8" intake 1-1/8" exhaust	1-3/8" intake 1-3/8" exhaust	1.3/8" intake 1-3/8" exhaust
	Guide Reamer Size		.3125"	.3125"	.3125"	.3125"	.3125"
	Tappet Clearance (Cold)	Intake	.006" (min.) .008" (max.)	.008" (min.) .010" (max.)	.008" (min.) .010" (max.)	.008" (min.) .010" (max.)	.008" (min.) .010" (max.)
		Exhaust	.017" (min.) .019" (max.)	.017" (min.) .019" (max.)	.017" (min.) .019" (max.)	.017" (min.) .019" (max.)	.017" (min.) .019" (max.)
	Minimum Lift (Zero Lash)	Intake	.2718"	.318"	.318"	.318"	.318"
		Exhaust	.2482"	.318"	.318"	.318"	.318"
	Minimum Stem O.D.	Intake	.3103"	.3103"	.3103"	.3103"	.3103"
		Exhaust	.3074"	.3074"	.3074"	.3074"	.3074"
	Face Angle - Seat Angle -		45º 46º	45º 46º	45º 46º	45º 46º	45º 46º
	Guide I.D. Maximum Wear Limit (note 1)	Intake	.006"	.006"	.006"	.006"	.006"
		Exhaust	.008"	.008"	.008"	.008"	.008"

Note 1 Subtract O.D. of inner part from I.D. of outer part.
Note 2 Champion spark plugs or equivalent.
Note 3 Measure just below oil ring and at right angles to piston pin.
Note 4 Measure 1/2" above the bottom of the piston skirt.
Note 5 Top and center compression rings.

Kohler K-Series - Single Cylinder Torque Values and Sequences for Fasteners
. (Click here to print out the below.)

Model (Horsepower)		K91 (4)	K161 (7)	K181 (8)	K241 (10), K301 (12), K321 (14), K341 (16) and K361 (18)
Connecting Rods (See notes 1 & 2)	Posi-Lock (Nut)	-	-	New 140 in. lb./12 ft. lb. Used 100 in. lb./9 ft. lb.	New 260 in. lb./22 ft. lb. Used 200 in. lb./17 ft. lb.
	Capscrew (Bolt)	140 in. lb./12 ft. lb.	200 in. lb./17 ft. lb.		285 in. lb./24 ft. lb.
Spark Plugs		234 in. lb./18-22 ft. lb	234 in. lb./18-22 ft. lb.		234 in. lb./18-22 ft. lb
Cylinder Head (See note 1)
Flywheel Retaining (See note 5)	Nut (See note 1)	40-50 ft. lb.	85-90 ft. lb. note 4		5/8" stud - 65 ft. lb. 3/4" stud - 170 ft. lb.
	Screw (3/8" bolt) (See note 1)	250 in. lb.	-		22-27 ft. lb./35 ft. lb.
Governor Bushing		70-90 in. lb.	130-150 in. lb.		100-120 in. lb.
Grass Screen	Metal	-	70-140 in. lb.		70-140 in. lb.
	Plastic	-	-		20-30 in. lb.
Oil Pan	Cast Iron (see note 1)	250 in. lb.	Grade 5-250 in. lb. Grade 8-350 in. lb.		35 ft. lb.
	Sheet Metal (See note 1)	-	-		200 in. lb.
Plastic Fuel Pump Mounting Screws		-	37-45 in. lb.		37-45 in. lb.

Note 1 - Lubricate fastener threads with engine oil.
Note 2 - DO NOT overtorque - DO NOT loosen and retorque the hex. nuts on Posi-Lock connecting rods. IMPORTANT! Over-tightening nuts or bolts can lead to fastener failure. And using an impact wrench without some type of torque limiting device can damage the threads in aluminum, especially the connecting rod.
Note 3 - Overtorque 20%, loosen below torque value and retorque to final torque value. NOTE: Overtorquing the rod bolts 20% places stress on the threads in a NEW aluminum rod. This allows for proper tightness so the bolts won't loosen later. Torque used rods to 285 in. lbs. and leave them at that.
Note 4 - Prior to Serial No. 23209832 - 45-55 ft. lb.
Note 5 - Flywheel and crankshaft tapers must be clean and dry.
NEW - Component directly from stock. USED - Component that was in a running engine.

My Other Engine Building Related Web Sites:

Information about Valves, Camshaft and Exhaust Header Pipe Information about the Cylinder Head on Single Cylinder Kohler Engines Ignition Solutions for Small Engines and Garden Pulling Tractors Information about Kohler Carburetors & Fuel Systems

Important Information about Small Engine Flywheels Important Information about the Cub Cadet Oil Pan Balancing the Crankshaft and Piston/Connecting Rod Assembly

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