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Vital Information about Engine Rebuilding, Buildups and Modifications |
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Vital Information about Engine Rebuilding, Buildups and Modifications |
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The Differences Between the Old Kohler K-series and the Newer Kohler Magnum Engines -
The Magnum engines replaced the older K-series in later years. The Magnum engines are basically the same engine as the K-series. The main differences are, besides the sheet metal that covers the block, the Magnum has solid state electronic ignition, a fixed main jet (Walbro) carburetor and the starter fastens to the bearing plate instead of the engine block. And there are no provisions for using ignition points. Most of the external and all the internal parts are interchangeable, and most aftermarket (high-performance) parts are interchangeable with either engine.
And if you're looking for some yellow paint to paint your Cub Cadet with, try your local farm and home supply store. They usually have International Harvester Yellow. It closely matches the color of Cub Cadet yellow.
Why Aluminum Block Engines (except V-Twins) Don't Work Well for Pulling Competition -
An aluminum engine block will "bend and twist" or flex 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.
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 rpms (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 are set closer to the piston (valve stems are angled). Therefore, the other engines can't build up as much compression as the Kohler engines can. Plus, they can't flow as much air in and out of the combustion chamber at high rpms, like the 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. I found that 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 rpms. Top of page
Converting a vertical shaft twin cylinder flathead B&S engine into a horizontal shaft model -
I've never tried this, but I believe it will work. 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.
I believe 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 -
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 covered with carbon, then the piston rings are in good condition. But if some of the carbon is washed away 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:
K90/K91 (4hp) |
7hp (K141/K161), 8hp (K181) |
10hp-16hp flatheads and 18hp OHV engines |
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STD. = 1.499" (minimum) 1.500" (maximum) |
.020" = 1.479" (minimum) 1.480" (maximum) |
Click HERE for Complete Kohler Single Cylinder Engine Specifications and Tolerances. |
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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 (6.6hp) 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...
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 -
Imported pistons, rings, rods and other parts hold up VERY WELL. I should know, I've used these parts in my own equipment and I've sold them to my customers. I've sold many of these parts for the past 26+ years and I haven't had one complaint from anyone. 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 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 rpms 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 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.
Identifying Kohler Crankshafts -
How to Remove Only the Crankshaft from a Kohler Engine -
Remove
the flywheel and anything that's on the PTO end of the crankshaft.
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 rpms, 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 we have no problems with the crank journal wearing. Heck, I've been using a .020" undersize bearing with the same crankshaft in my 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 rpms 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. 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.
How to Fix a Broken Off Crankshaft Stud (this happens a lot, by the way):
Another method to fix a broken off stud on a crankshaft with the crank out of the engine -
Basically, grind the remaining stud off the end of the crank, and then drill and cut threads for the 3/8" fine thread bolt. And if you're going to use a hub and run like a Cub Cadet clutch or a pulley, the bolt must be centered exactly in the crankshaft. Otherwise, it'll wobble.
Advertisement: (Updated 1/23/08)
| If you need any of the services performed or items listed
below, please contact me, Brian Miller, at A-1 Miller's
Small Engine & Specialty Shop (1501 West Old Plank Rd., Columbia,
Missouri. 65203 | Phone: 1-573-875-4033). Please call any day between 12
noon and 8:00 p.m. Central time, and please be patient because I stutter.
Fax: 1-573-449-7347. You can also contact me through Yahoo! Messenger:
|
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Crankshaft Repairs -
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 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.] 
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 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. $15.00 each, plus shipping.
Part #150-973
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. $10.00 each, plus shipping. Part # 150-960 NOTE: If you cleaned all the oil out of the crankshaft main [ball] bearings and then allowed them to dry, and then later you spun the bearings by hand, and if the bearings isn't worn much or at all, they might feel "rough" and make a rattling sound. This roughness or noise isn't necessarily because the bearing is worn out. The noise is mainly caused by the balls running dry on the races because there's no oil to separate them from the races. Try applying a small amount of motor oil to the balls/races and then spin them. They should be a lot quieter. The same thing will happen with new ball bearings. |
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 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. |
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 Oil Drain Valve.
Has 3/8" NPT (right hand) threads. Universal fit. Easy to use. NOTE: Valve
has left-hand threads. $7.00 each, plus shipping. |
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 Flywheel retaining nut for crankshaft studs with 5/8-18 NF or 3/4-16 NF threads. Self-tightening jam nut. Guaranteed to stay tight! Torques at 65 ft. lbs. $1.00 each, plus shipping. |
 Flat washer for retaining flywheel and/or aluminum clutch hub adapter to flywheel. A must to secure flywheel and to prevent hub breakage! Available for a 5/8" or 3/4" stud. 1-1/4" o.d. x approximately 1/4" thick. $2.00 each, plus shipping. |
 Steel adapter step-washer for mounting the aluminum clutch hub with a 5/8" hole to the Kohler Magnum crankshaft with a 3/8" bolt. A must to prevent hub breakage! $8.00 each, plus shipping. NOTE: I can also custom machine other adapter washers to fit your particular application. All I need is the dimensions. $10.00 each, plus shipping. |
How to Remove and Replace the Governor Gear Assembly in a Single Cylinder Kohler Engine -
Be sure to remove and save the small thrush washer that's on the governor
gear's stub shaft! (A lot of people are not aware of this
hardened/heat-treated washer and it usually falls off and gets lost while
washing inside the block.)
Plastic VS Cast Iron Governor Gear Assemblies -
The most popular 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, 7hp, early 8hp, 10hp and 12hp K-series Kohler engines 'til the late
1960s. (I don't know what year Kohler stopped making them.) 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.
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 rpms. 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. And don't worry, as long as the governor linkage is adjusted correctly, the plastic governor gear assembly should hold up fine in an engine that will never operate above 4,000 rpms. 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. |
Plastic governor gear. |
Advertisement:
| If you need a governor gear assembly,
please contact me, Brian Miller, at A-1 Miller's Small
Engine & Specialty Shop (1501 West Old Plank Rd., Columbia, Missouri.
65203 | Phone: 1-573-875-4033. Please call any day between 12 noon and 8:00
p.m. Central time, and please be patient because I stutter. Fax: 1-573-449-7347.
You can also contact me through Yahoo! Messenger:
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 Material:
$12.00 each, plus shipping. Good for up to 4,000 rpms. OEM Kohler
part # A235743S. [When available.] |
 Cast Iron Material:
$40.00 each, plus shipping. These won't break at high rpms. No
longer available from Kohler. [When available.] |
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 rpms 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.
Advertisement: Top of page
 If you need a Precision Handheld Tachometer,
please contact me, Brian Miller, at A-1 Miller's
Small Engine & Specialty Shop (1501 West Old Plank Rd., Columbia,
Missouri. 65203 | Phone: 1-573-875-4033. Please call any day between 12 noon
and 8:00 p.m. Central time, and please be patient because I stutter. Fax:
1-573-449-7347. You can also contact me through Yahoo! Messenger:
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 rpms 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. |
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, I've always
used paint thinner to clean my engine parts. I get it at Wal-Mart. That's
the cheapest place I've found.
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 my 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 enters an engine smoothly.
ü Check the
ignition timing. Chances are, if the timing isn't
advanced enough, 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 my 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 your engine...
In order for an engine to turn at extremely high rpms (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. To raise the compression and increase the air flow on a flathead engine....
The only things that can cause an engine to overheat and loose power are as follows:
How To 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! Rather if it's used for pulling competitively or just for yard work, a "built to the max" stock engine will perform much better with the modifications listed below...
Here's Some Basic External and [Fairly] Low Cost Performance Improvements That Can Be Done:
Remove the flywheel fins ONLY if an engine is governed up to 4,000 rpm, and
absolutely have a [cast iron] flywheel dynamically precision-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.
You can have your Kohler flywheel and
crankshaft/piston/rod assembly professionally dynamically precision balanced
at:
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But if you want more power out of your engine, more internal work is involved....
If
there's carbon covering the top of the pistons, this means that the engine
doesn't burn much oil, if any. But if there's some oil on top of the pistons
and some of the carbon is washed clean, this is an indication of oil burning
and the engine needs to be rebuilt. If your engine doesn't produce blue smoke
out the exhaust (doesn't burn oil), then it should be okay to reuse the same
piston and rings. Because there's probably not that much wear on them. When
reinstalling a used piston/rings though, oil the rings and install the piston
with the ring gaps set 180º apart. But if your engine does smoke and
use oil, it'll be best to have the cylinder measured for wear and perhaps
bored to the next oversize, or if it's within tolerance, just install a new
STD size piston and rings assembly.
And the
ALCOA connecting rod that originally
came in all 18hp OHV (K361) engines are even stronger yet. And as far I've
seen, most of the 14hp and 16hp rods are the same. Although some 14hp's (and
12hp's) came from the factory with the weaker "two color" rod. But some 12hp's
also came from the factory with the stronger 16hp rod. And ALL 18hp rods
are made of forged aluminum alloy. They're the strongest of any rods that's
used in Kohler engines.
If
you're going to turn your engine no faster than 4,000 rpm, an ordinary 12hp
or 14hp "two color" rod should suit it just fine. But higher rpms requires
a stronger rod. 16hp rods are good for up to around 6,000 rpm. But the 18hp
rod is good for well above 6,000 rpm. By the way, the new 16hp rod is designed
for the new-style 16hp piston, but it'll work with any 12hp or 14hp piston
with no problems. Also, all 16hp rods come with a long oil dipper.
So if you're using a flat bottom oil pan, you'll need to cut half of the
dipper off with a hacksaw and smooth up the rough edges with a flat file.
Be sure to sharpen the edge of the dipper with the file so it'll slice through
the oil with less resistance. It'll still provide plenty of lubrication,
too. (A "blunt" dipper has a tendency to rob horsepower.) And it's safe to
reuse a stock rod in a 10hp engine. They're strong rods. And being the engine
is going to be operated at a maximum of 4,000 rpm, there's no need for bearing
inserts.
Install an OEM camshaft that's
originally made for Kohler's model K361 18hp Over Head Valve engine. NOTE:
The "18hp cam" originally came in the model K361 18hp single cylinder Kohler
engine that have the valves in the cylinder head but the camshaft in the
crankcase. This particular cam has the same lift as the 10-16hp flathead
engine cams (.324"), but increased duration from 223º (flathead cam)
to 256º (18hp OHV cam), which will produce more power and torque at
4,000 rpm when used in a flathead engine. This particular cam makes it's
most power and torque up to 4,000 rpms, which works great in a stock engine.
If an engine is going to be turned faster, then a cam with more lift and
duration should be used for best performance. And when installing this cam,
align the timing marks (on both the crankshaft teeth and cam teeth) as you
would with virtually any other engine, and use a thick shim (.010") and/or
a thin shim (.005") on the flywheel end so the cam will be in proper time
in relation with piston travel. It's important that the compression relief
mechanism on the camshaft is functioning properly, too. The compression relief
mechanism is required to relieve some of the higher compression at cranking
speeds so the engine will crank over easy to start it. FACT: The 18hp OHV
cam works so well in the 10-16hp flathead engines, many clubs are outlawing
it in their stock class(es). And to swap out the cam, you must first disassemble
the entire engine. The pin that the cam rides on must be driven out from
the PTO side of the block. (It comes out toward the flywheel end.) VERY IMPORTANT
- Before installing any Kohler camshaft, be sure to lubricate the pin and
the inside of the camshaft before reinstalling! And if the base of the lifters
aren't worm or scored, they can be re-used. By the way - the lifters in the
10, 12, 14 and 16hp flathead engines and the 18hp OHV engine are all the
same. The 18hp camshaft comes with a compression relief. By the way - the
18hp cam doesn't have enough duration to make the engine have a "loping"
sound at idle. It makes the engine sound like a stock short-duration
cam.
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. But doing the things below should boost the horsepower of these engines about 2-3hp more at 4,000 rpm.
* 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 rpms.
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 the characters K301 embossed in the casting above 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. In other words, they're like the 13-fin 16hp block.
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 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.
If built to stock specs, it'll produce about 14hp at 4,000 rpm. But if it's built to the max, it'll produce about 22hp 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:
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How to Create a 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.
If built to stock specs, it'll produce about 11-1/2hp at 4,000 rpm. But if it's built to the max, it'll produce about 16-1/2hp 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:
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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:
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:
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. |
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 rpms, 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. We 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 of Midwest Super Cub (http://www.midwestsupercub.net/) |
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 assembly. But there's really no need to do this, and it won't give it 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 good 12hp engine will actually pull you back in the seat when you punch the gas. Not only because the 12hp has an 1/8" larger bore than a 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 because the 12hp use a cylinder head with the same size combustion chamber as the 10hp. But there's not that much of a noticeable difference in power and torque between a 12hp engine and a 14hp, 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 because they use a cylinder head with the same size combustion chamber as the 12hp.
A longer-than-stock stroke works better for more engine torque because at very high rpms (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 rpms 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 the same principles. Racing engines requires horsepower (speed) and pulling engines requires 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 ran out of power, the stroker engine will keep on lugging on out the gate.
Example: The 7hp and 8hp Kohler engines 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. 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:
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, I recommend that
the cylinder should 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 my engines, I don't install threaded rods in the block itself. 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:
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.)
The .003" interference fit makes for a perfect press fit. Do not make it
any tighter or the cylinder could split or crack!
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 engine and then bore it for a STD size piston assembly. |
If methanol is going to be burned in the engine, and because the engine will
have a thinner cylinder wall with increased compression, I highly recommend
fastening the cylinder 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, I'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.
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.
Install an Auxiliary Crankcase Breather for Better Engine Venting Above 4,000 rpms...
The factory crankcase breather alone
isn't adequate for all high-performance single cylinder engines, especially
big cubic inch engines running at all-out rpms. They build up more pressure
in the crankcase due to the longer stroke. The downward movement of the piston
will force air out of the crankcase. At very high rpms (well above 4,000
rpms), 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 stock breather at
very high rpms, it will sometimes take some crankcase oil with it, spewing
an oily mess on the track. So if your engine has this problem (not all engines
spew oil at high rpms), 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 (click on it for a larger view), 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 up, the less time air has to exit
and re-enter the crankcase. In other words, at very high rpms, 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. Besides, the breather has a filter in it. So
if any [dusty] air does enter in the crankcase, it's filtered air.
By the way - this auxiliary crankcase breather doesn't help to make more horsepower. It just keeps oil off the track and in your engine
How to make an auxiliary breather for better crankcase venting above 4,000 rpms...
Universal
crankcase oil breather cap (Mr. Gasket part # 9810 or equivalent) or a MOPAR
crankcase breather (oil filler cap) that's made for a 1972-1989 Chrysler
or Plymouth, 1971-1998 Dodge car or light truck, or a 1993-1997 Jeep vehicle.
These are nothing but a small air filter with a 1-1/16" o.d. fitting. See
images to the right for correct identification.
è
Using the hammer and pointed
chisel, or use the hammer and long 3/8" diameter steel rod to remove the
welch plug from inside the crankcase, remove the welch (expansion) plug from
the PTO end of the [Kohler] engine block. See the picture to the right for
location of this plug. è Completely disassemble the engine before performing this
step, as metal cuttings will enter the crankcase and cause excessive wear
to the internal moving parts!
If you connect a breather hose from the crankcase to the exhaust pipe, to relieve crankcase pressure to act as a scavenging effect, you will need to also install a one-way check valve. (Like an automotive PCV valve.) Because as your engine backfires, it could set the oil on fire inside the engine, or cause a crankcase explosion. Especially if there's a lot of methanol or gas mixed with the oil.
And if there's a problem with motor oil seeping or blowing out of the crankcase breather, attach a hose to the breather and route it down under the tractor, let the oil drain on the ground. Because the oil will ruin the pleated paper air filter if it was attached to the air filter breather assembly.
Prepping the Block for Installation of the Piston Assembly -
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, and glides over the oil on its way up and scrapes it on it's way down. 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 more or less square edge. If a piston is worn in the cylinder, this will cause the edge of 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.
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Installation of rings on the piston are as follows:
Never attempt to install piston rings in reverse order or they might break upon installation!
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. That's why it's called the expander. It "expands" the two thin oil lubricator rings so they can press against the cylinder wall to work better.
Make sure the middle ring is installed correctly! This step is very important! It 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. If the middle ring came with an expander (rippled spring-like ring), install it under the ring. It helps to stabilize the piston in the cylinder.
NOTE: I've seen second rings where they have the word TOP scribed on them with the chamber facing upward. This gets confusing because of all the second rings that I've seen over the years with no indication of how they're installed, the instructions says that the chamfer faces downward. But there's a reason why the manufacturer would stamp their rings or want them installed a certain way. So I guess just install it the way the manufacturer recommends and hope for the best.
As for the top ring, if it has square edges with no chamfer or bevel, then there's no certain way how it installs on the piston, being it just holds the compression. If any of the rings have a dot or small indention stamped into them, the dot or indention always faces upward. Or they may have the wording "TOP" laser-etched on them.
NOTE: If the top and/or middle rings were installed incorrectly, and if the engine smokes, the rings can be removed and installed in their correct position and be reused. Because very little wear has occurred to them. There is need to purchase a new set of rings due to improper installation. Because installing rings upside-down doesn't necessarily cause them to wear more, they just may cause the engine to smoke out the exhaust.
Instructions on how to install the rings should be on or in the box that 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 them a little longer to seat and they last a lot longer. Go here for more information: http://www.totalseal.com/howdoo.html.
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 assembly 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 rpms.
Advertisement:
| If you need a new ring set or a new piston/rings assembly, please
contact me, Brian Miller, at A-1
Miller's Small Engine and Specialty Shop (1501 West Old Plank Rd., Columbia,
Missouri. 65203 | Phone: 1-573-875-4033. Please call any day between 12 noon
and 8:00 p.m. Central time, and please be patient because I stutter. Fax:
1-573-449-7347. You can also contact me through Yahoo! Messenger:
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| NOTE - I can get complete engine rebuild kits, but a kit cost me more than if I were to order the parts individually. So please email me or call me with a list of which parts you need, and I'll get back to you with a total including shipping. And if you need a part or parts that's not listed here or for other make and model of engines, please contact me and I'll see if I can get it at a reasonable price. Please contact me 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 noise in the engine. A series of events will then soon happen:
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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 rpms. And yes, when properly balanced, even a cast iron crankshaft will flex a few thousands of an inch at high rpms 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:
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/), Nichols Performance (http://nicholsperformance-online.com) 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:
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 rpms.
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. If the crank has too much end play on a horizontal shaft engine, the piston will wobble side to side in the cylinder and the rod will also wobble on the crank (much like the clapper in a bell). Also, on engines such as the cast iron block Kohler with helical (angled) teeth on the crankshaft and cam gear, too much crankshaft end play will effect the valve timing. On vertical shaft engines, the piston will operate diagonally in the cylinder. This diagonal movement of the piston will cause the rings, wrist pin and rod bearing surface to wear unevenly and prematurely. At high rpms, the crankshaft can move back and forth so quickly, the wrist pin in the piston couldn't react quick enough to compensate for the excess movement. Too little crankshaft end play will also cause "bearing whine or howl," which sounds like a whining or howling noise coming from the engine at faster speeds. The engine may also slow down at high rpms. But if the crankshaft has too little end play, the main bearings will run tight, causing the crankshaft to bind and the engine to slow down when the 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 spin the same rpms
as the engine. If there's not enough crankshaft end play, and the faster
the engine runs, the balls in the main bearings will spin 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
run hotter yet. And when this happens, they swell a few thousands of an inch.
As they swell, crankshaft end play is taken up and crankshaft binding occurs,
which effects engine performance. When rebuilding an engine, this is why
it's so important to set proper crankshaft end play. I think that OEM Kohler
8-ball main bearings works best in a high performance engine. Kohler engineers
knew what they were doing when they designed the Kohler engine.
The gaskets on the bearing plate of a Kohler engine are also shims. Add or subtract gaskets until the proper clearance for crankshaft end play is gained. 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 clearance. To set the clearance, install several thick (.030") and/or thin (.015") gaskets between the crankcase and bearing plate until the desired clearance is achieved. The end play on the 10-16hp flathead Kohler engines and the 18hp OHV Kohler engine 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 engine 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.
If you were to wash all the
oil out of the crankshaft main [ball] bearings with cleaning solvent and
allow them to dry, and then later you spun the bearings by hand, and if the
bearings isn't worn much or at all, they might make a rattle sound and feel
"rough." The noise or roughness isn't necessarily because the bearing is
worn. The noise is mainly caused by the balls running dry on the races because
there's no oil to separate them. Apply a small amount of motor oil to the
balls/races and then spin them by hand. They should be a lot quieter now.
The same thing will happen with new ball bearings. And if the bearings have
very little play in them, like they're worn, don't worry about this. The
metal will swell up as the engine rpms increase and when the motor oil warms
up. Even new bearings have little play in them for this reason.
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.
Advertisement:
| If you need a new or used 10hp, 12hp, 14hp, 16hp or 18hp connecting
rod, or if you wish to have your 10hp-18hp connecting rod fitted with bearing
inserts, please contact me, Brian Miller, at
A-1 Miller's Small Engine and
Specialty Shop (1501 West Old Plank Rd., Columbia, Missouri. 65203 |
Phone: 1-573-875-4033. Please call any day between 12 noon and 8:00 p.m.
Central time, and please be patient because I stutter. Fax: 1-573-449-7347.
You can also contact me through Yahoo! Messenger:
IMPORTANT: Install connecting rod on crankshaft with match marks aligned and oil hole towards camshaft. And if using a shallow oil pan, cut half of the dipper off the rod. It won't hurt a thing.
New STD size 8hp (K181 & M8) K-series and Magnum flathead engine connecting rod. Replaces Kohler part # 41-067-10. Bearing inserts are not available for this particular rod. $30.00 each, plus shipping.
10hp Connecting Rod -
12hp, 14hp and 16hp Connecting Rods -
If you need a new 18hp (K361) OHV Kohler engine
ALCOA connecting rod,
visit your local Kohler engine dealer or contact Elson Nichols of Loop 70
Auto Parts &Machine, 14 Bus. Loop 70 East, Columbia, Missouri 65201.
Phone: 1-573-449-0893. Email:
vjnen@centurytel.net. Genuine Kohler
part # 45-067-15S (STD) or 45-067-17 (.010" undersize, with no bearing) comes
with a long dipper. Very strong rod! Good for up to 6,000+ rpm!) Comes with
no bearing inserts, but I can bore rod and install bearings if you wish.
5.3" length. NOTE: Comes with no bearing inserts, but I can bore rod and
install bearings if you wish. Machine Work:
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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 rpms. 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.
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 -
If an 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 bearing inserts wear [only due to lack of proper lubrication], 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 before it breaks.
If this happens, turn the engine off immediately and replace the damaged
bearing, and then install the proper grade of oil to the full level! But
the hole in the rod can become oblong or "egg-shaped" after taking a pounding
from a worn bearing. So it may have to be re-bored (resized) first to make
the hole a perfect circle again. It'll be wise to check the rod for stress
cracks with a strong magnifying glass or better yet, a microscope. 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.
Remember this: due to lack of lubrication and/or at very high rpms, an ordinary aluminum surface connecting rod will most likely score the crank journal, and the rod will likely break, sometimes destroying the engine. As long as the crankcase is full of oil (splash oiling system) or adequate oil gets to the bearings (oil pump system), and as long as the they have adequate oil clearance, bearing inserts will hold up to unlimited engine rpms. Return to previous paragraph. È
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 rpms 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 rpms. 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 rpms.
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.
Fitting a Connecting Rod with Bearing Inserts -
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.
By the way - I'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+ rpms. So it's a safe thing to do. Besides, I wouldn't have mentioned it here if it didn't work.
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 rpms). 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.
Inserting bearing inserts in a Kohler rod doesn't weaken it 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 rpms.
Installing bearing inserts in a rod for a Kohler engine would cost much less than purchasing a new or even used crankshaft and/or rod, 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 on the crank journal.
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. One bearing manufacturer is Clevite 77. Their part numbers are CB-278 P or CB-279 P. (Clevite 77 bearings are also sold under brand names Sealed Power and Muskegon.) Another manufacturer is Federal-Mogul. Their part numbers are 9885CP or 9885CPA. Undersized bearings are indicated by adding either 10 (.010"), 20 (.020") or 30 (.030") after the part number. The difference in the two part numbers is the locking tangs are located opposite than the other.The difference in the two part numbers is the locking tangs are located opposite than the other. These bearings are available in STD, .010", .020" and .030" undersizes. Add either 010, 020 or 030 after the part number to indicate the correct undersize bearing that's needed. One brand of bearing is just as good as the other. 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 engine.
You can get quality Clevite or Federal Mogul bearing inserts from virtually any place that sell automotive engine parts or high-performance aftermarket garden tractor engine parts (A-1 Miller, Lakota Racing, Midwest Super Cub, Vogel Manufacturing Co., Sterling Bearing, Inc. 601 Truman Rd. Kansas City, MO 64102 Phone: 1-800-821-5148, 1-816-842-1887, fax: 1-816-842-8447) and most auto parts supply stores can also get these bearings. Actually, any place that sell automotive bearings should be able to get these bearings. If they say they can't get them, then they're not looking hard enough. They retail for about $12.00-$13.00 each.
FYI - 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) for installation of the bearing.
How to install bearing inserts in the 10hp-18hp Kohler connecting rods -
First of all, make sure that the rod and cap are both clean, and that the cap is installed correctly on the rod. There should be alignment marks on the cap and rod. Then torque the cap to the rod according to factory specifications.
There are two methods to accurately bore Kohler connecting rods. Method one is with a vertical milling machine...
First,
the centerline of the big end of the rod must be at an exact vertical plane
with the centerline of the spindle in the milling machine. In other words,
they must be perfectly inline with each other, unless the table is moved
.020", then the rod bearing will be offset in the rod .020" for piston pop-out.
Center the rod with the spindle using a "step" plug alignment tool. Fabricate
this tool with a 1.500" diameter plug for STD size rods, and 1.490" plug
for .010" undersize rods. Make sure the rod is perpendicular with the spindle,
too.
NOTE: Sometimes after the boring process, the
hole will be offcenter, to the side (which will effect nothing by the way)
and one of the rod bolts or studs may interfere with the bearing. If this
happens, grind away part of the bearing shell so it'll clear the bolt or
stud.
After drilling the oil hole, the
burr of metal inside the bearing will need to be chamfered and removed with
a small pocket knife. Removal of the burr is very important to prevent it
from possibly ruining the bearing, rod and scoring the crank
journal!
Another method to bore Kohler rods is with a specially-designed machine that's used to remove the babbitt material from Model A Ford connecting rods. (These particular bearings fit the Model A Ford rods too, with the rods bored and honed to 1.625".) First use this machine to cut the majority of the metal from the rod until the hole is enlarged just under 1.625", then finish-hone the bore with a connecting rod honing machine to 1.625".
When installing the rod and piston in the block and after the rod is connected to the crankshaft, sometimes there can be a clearance problem with the rod hitting the edge of the cylinder. That's because of the offset of the bearing in the rod. To fix this problem, just grind away part of the cylinder until the rod clears. Remove just enough metal from the cylinder wall so a .050" diameter wire can clear between the cylinder wall and connecting rod. That's all the clearance it needs. Return to previous paragraph. È
And if a rod burns on the crankshaft in an engine, the causes are either:
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 rpms. At high rpms, 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 rpms 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 rpms.
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:
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
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 I said above is what most manufacturers suggest to use [non-detergent oil] in their non-filtered small engines, which does make sense. And I guess 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 rpms (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 my 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.
Synthetic oil is mainly used in high-revving and high-performance engines that operate at higher rpms 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 rpms 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. An engine will still wear out. In this world, nothing lasts forever. Everything eventually wears out. Besides, if oil refineries thought that an additive would help an engine last longer, they would go ahead and put it in their oil. Additives is just something to get people's money, nothing more.
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."
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 rpms. 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 check that the dipstick is calibrated correctly, on the single cylinder 10hp-16hp Kohler engines, with the dipstick in the tube, hold them next to the outside of the block and observe where the FULL mark is. The FULL mark should come to about 1/2" above the oil pan gasket flange. If it's not right, then the dipstick or tube may have to be shortened or lengthened. And always fill an engine with oil to the FULL mark on the dipstick. Return È
Checking the Compression Pressure on a Stock and High-Performance Engine -
First of all, the compression release (or relief, as it is sometimes called) is either a small lump (B&S, Tecumseh, etc.) or mechanical lever (Kohler, 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. It releases about half of the combustion chamber pressure at cranking speed so the engine will start with fixed advanced ignition timing. If the compression release isn't working, the engine would "kick back" every time when trying to start it because of the fixed advanced ignition timing.
On OEM camshafts with a working compression relief mechanism and if the valves are adjusted to specs, the compression relief relieves about half the compression from the combustion chamber at cranking speeds. 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. 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 has. And 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, I multiple 100 by 285 (duration of cam that's in the engine) and then I divide the answer by 223 degrees (duration of a stock OEM cam), which gives me 128 psi.
How To Prepare an Engine for Wintertime or Long-Term Storage -
How to Tell the Differences Between the 10hp, 12hp, 14hp and 16hp Kohler Engine Blocks -
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 me, Brian
Miller, at A-1 Miller's Small Engine & Specialty
Shop (1501 West Old Plank Rd., Columbia, Missouri. 65203 | Phone:
1-573-875-4033. Please call any day between 12 noon and 8:00 p.m. Central
time, and please be patient because I stutter. Fax: 1-573-449-7347. You can
also contact me through Yahoo! Messenger:
Balancing Service -
Engine Block -
Valve Train Related -
Cylinder Head Work -
Crankshaft Repairs-
Connecting Rod -
|
Advertisement:
Brian Miller's Engine Rebuilding and Build-Up
Service - (updated 8/8/07)
| If you need your engine rebuilt or built up for pulling
competitively or so it'll produce more power and torque, please contact me,
Brian Miller, at A-1 Miller's
Small Engine and Specialty Shop (1501 West Old Plank Rd., Columbia, Missouri.
65203 | Phone: 1-573-875-4033. Please call any day between 12 noon and 8:00
p.m. Central time, and please be patient because I stutter. Fax: 1-573-449-7347.
You can also contact me through Yahoo! Messenger:
|
|||
 Bare Kohler K-series Engine Blocks (when available) -
Top of page
|
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| I rebuild ordinary stock engines and build high performance 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 to 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.
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 maximum horsepower and torque, or the factory-rated horsepower and last a long time. I do what the repair manual says plus some. 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. I also rebuild ordinary lawn & garden equipment engines too, such as single cylinder and twin cylinder flathead and v-twin OHV Briggs & Stratton, Kohler, Tecumseh and 2-cycle LawnBoy.
Engine Refreshening Service -
|
|
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Details below are as follows for a complete(±) engine or shortblock: (updated 9/28/07)
NOTES:
The higher prices include rebuilding everything on and in the engine; includes the carburetor reworked, exhaust header pipe, ignition components, starter, etc., depending on rules requirements, what you want done and how "hot" you want your engine to perform. A deposit is required on all engine rebuilds. If you decide to ship an engine to me, enclose it in a wooden crate or cardboard box fastened on a wooden pallet. To build a sturdy 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 around and above the engine (cover the engine with plastic or a garbage bag first) 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 me in person, sit it in an old tire to keep it from moving around during transportation. And please let me know first so we 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 me, first off, do not use the US Mail Service, UPS or FedEx Express! Their 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. Here's a great web site that calculates freight charges. Go here: http://www.shipgooder.com/ and type in your zip code, my zip code (65203) and the crated weight of a typical complete 10-16hp Kohler engine (145 lb.). 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. 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 I say this is because I 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. To ship an engine, freight companies require it to be in an enclosed wooden or plastic crate, or a sturdy cardboard box. It's best to securely fasten it with the oil pan bolts on a pallet made of 2 x 4's and fasten the boards together with long drywall screws, not nails. Then place a 2 x 2 wooden frame around the pallet and fasten 1/4" plywood with a 2 x 2 frame work. Run cross-braces which encompasses the top portion of the cylinder of the block. This will support or stabilize the top of the block and keep the engine from getting ripped off the base. Put a lid on the top and then load it in the trucking company's truck when it arrives with a tow motor. You shouldn't have any problems shipping an engine this way.
For other high performance engine builders, contact either Lakota Racing - Quarter Scale Performance (http://www.lakotaracing.com), Midwest Super Cub (http://www.midwestsupercub.net), Nichols Performance (http://nicholsperformance-online.com) or Vogel Manufacturing Company (http://www.vogelmanufacturing.com). |
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I don't build 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. They can answer your questions.
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 @ 4,000 rpm) | K141 (early)
(6.6hp) K161 (late) (7hp) |
K181 (8hp) | K241 (10hp) | K301 (12hp) | K321 (14hp) | K341 (16hp) |
K361 (18hp) (Over Head Valve) |
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| 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.) |
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| 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 (early) K91 (late) (4) |
K141 (early) K161 (late) (7) |
K181 (8) | K241 (10) | K301 (12) | K321 (14) | K341 (16) | K361 (18) (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 (early) K91 (late) (4) |
K141 (early) K161 (late) (7) |
K181 (8) | K241 (10) | K301 (12) | K321 (14) | K341 (16) | K361 (18) (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.
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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
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
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. 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 these rings will not fit
Mahle pistons that originally come in Magnum engines. $14.00 each
set.
8hp Connecting Rod -
New STD size 10hp (K241, M10)
K-series and Magnum flathead engine connecting rod. Replaces Kohler part
# 47-067-13; comes with a long dipper. Strong rod. Comes with no bearing
inserts, but I can bore rod and install bearings if you wish. 5.558" length.
Used "two color" STD size connecting
rod. Fits 12hp (K301, M12), 14hp (K321, M14) and 16hp (K341, M16) Kohler
K-series and Magnum flathead engines. Genuine Kohler part # 47-067-09; 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 no bearing inserts, but I can bore rod and install bearings
if you wish. 5.3" length. $15.00 each, plus shipping. [When available.]
New 12hp (K301, M12), 14hp (K321,
M14) and 16hp (K341, M16) Kohler K-series and Magnum flathead engine connecting
rods. Replaces Kohler part # 45-067-22; comes with a long dipper and 3/8"
thread-in bolts. Strong rod. These were in stock engines that never exceeded
3,600 rpm for a long period of time. Comes with no bearing inserts, but I
can bore rod and install bearings if you wish. 5.3" length. Your choice of
either STD size or .010" undersize (no bearing inserts). $32.00 each,
plus shipping.
Quality Clevite 77 connecting rod bearing inserts:
$13.00 each, plus shipping. (Federal Mogul no longer available.)
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.
K301 embossed on the PTO end.
(Extra thick cylinder wall.). $100.00 each, plus shipping.
3hp to 5hp Briggs & Stratton
flathead aluminum block engine
(horizontal or vertical shaft) rebuild to OEM factory specifications @ 3,600
governed rpms (for general yard work only)
flathead
aluminum block engine (horizontal or vertical shaft) rebuild to OEM factory
specifications @ 3,600 governed rpms (for general yard work only)
2-cycle engine
(lawn mower models C, D & F) rebuild to OEM factory specifications @
3,200 governed rpms (for general yard work only)
flathead cast iron block engine rebuild to OEM factory specifications @ up
to 4,000 governed rpms (for general yard work or mild competitive pulling)
Stroked Kohler
Briggs & Stratton