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Balancing a Single Cylinder Engine Crankshaft and Piston/Connecting Rod Assembly to Reduce Dangerous Vibration
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Where Science and Common Sense Come Together for Better Engine Performance
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The basis of improved engine performance is precision workmanship. Every effort must be made to reduce friction and step up power. It must be remembered that extreme accuracy in setting the ignition timing, carburetion, together with a quality valve job, will give better than average performance. Contributing largely to stepped-up performance is precision balancing of the piston assembly and the connecting rod to the crankshaft counterweights. A special dynamic balancing machine or an electronic digital scale is used for balancing the piston assembly/rod to the crankshaft so the total weight of the piston assembly/connecting rod is exactly the same as the crankshaft's counterweights. Also, precision balancing of the rotating assembly and flywheel and low vibration saves wear and tear on internal engine components and attached external equipment.

If bolts, screws or nuts on the engine or tractor frame loosen due to engine vibration, there's no need to apply Loctite on the threads of the fastener. Just install a split lock washer of the correct size that fits the fastener (under the head or nut) then torque the fastener to specs. The lock washer will guarantee the fastener will stay tight. Or a self-locking nut can be used instead.


Here's some important information to remember - (Updated 3/7/18)

First of all, Kohler (and all other engine manufacturers) [obviously] balance their engines at the factory. The crankshafts' counterweights are equally balanced to the weight of the piston assembly to reduce engine vibration. The crankshafts that's are used in the K301, K321, K341 and K361 engines have the same stroke. The crankshaft in the K321 and K341 Kohler engine, and the K361 Kohler engine are identical (except perhaps for the PTO end). Therefore, they're balanced the same and can be used in either engine. All these engines have the same stroke, too. Only the counterweights are different. More metal is removed (drilled and machined off) from the counterweights for the K301 engines, which use a lighter weight piston than the K321, K341 and K361 pistons. The K301 crankshaft and piston assembly are a balanced set. Kohler use the same identical piston in their K341 and K361 engines. Although the connecting rods in these engines are made of different material, they weigh the same. Therefore, the crankshafts are balanced the same. The wrist pin is narrower in the K341 and K361 piston, making them weigh pretty much the same as the K321 piston and wrist pin.

HOWEVER, certain factory-type pistons come with a heavy wall wrist pin (weighs more), and others come with a thin wall wrist pin (weighs less). I believe that all OEM Kohler pistons come with a thin wall wrist pin, and most (or all) imported pistons come with a thick wall wrist pin. I'm not sure if there's a difference in the weight of the pistons themselves, and if this is why the manufacturer included a heavy or lightweight wrist pin to compensate for the weight of the piston to maintain engine balance. Anyway, to reduce the chance of severe engine vibration, use the heavy wall wrist pin in an engine that's going to run up to 4,000 RPM, and use the thin wall wrist pin in an engine that operates at a higher RPM.

The same crankshaft can be used with the K321, K341 and K361 piston assembly. If both counterweights on your crankshaft aren't machined off flat, then it's a 14 or K341 crank. If they are machined off, then it's a K301 crankshaft. And a K301 crank shouldn't be used with a K321 or K341/K361 piston assembly. The engine will vibrate more than usual and because of the heaver piston assembly, the connecting rod could stretch and eventually break. If a K321, K341 or K361 crank is used with a K301 piston, because of the heavier counterweights, the crankshaft could eventually break. Because there's one opposing force working against the other. ("For every action, there's an equal and opposite reaction." - Newton's third law of motion.)

In other words, the K301 crankshaft is balanced differently from the K321, K341 and K361 engine crankshafts. Although the stroke and rod journal are the same, the counterweights on the K301 crank are different. The K301 piston assembly weighs less than the K321 and K341/K361 piston assemblies. Therefore, the K321, K341 and K361 crankshafts require more metal on the counterweights to balance out equally. And K321, K341 and K361 crankshafts are all balanced the same, which means that they're interchangeable between the K321, K341 and K361 engines.

Because of it's shorter stroke, the K241 crankshaft is different from the K301, K321, K341 and K361 cranks. The K301 crankshaft's counterweights are machined flat for the lighter-weight K301 piston/rings assembly, while the K321, K341 and K361 crankshaft's counterweights are rounded for the heavier K321, K341 and K361 piston/rings assemblies. The same crankshaft is used in the K321, K341 and K361 engines because their piston/rings assemblies weigh the same.

The diffence between the 12hp crankshaft and the 14hp and 16hp crankshafts.

There's two types of K301 Kohler crankshafts. One is the early type. Its counterweights are the same width, and they're rounded with holes drilled. (Certain K241 crankshafts are like this, too.) The later K301 cranks have one wide and one narrow counterweight and both of them are machined flat to lighten them.

The crankshaft to the right is the very early model K301 version, because the counterweights are the same width. This crankshaft was produced in 1966-early 1969, before the K321 (and the K341 and K361, which share the same crankshaft because the piston assemblies are balanced the same) came into production. The K321 went into production in late 1969. The counterweights on the crankshaft for the K321, K341 and K361 engines, one is narrow and the other is wide. When the K321, K341 and K361 engines were manufactured, Kohler stopped making this type of crank and used the K321, K341 and K361 crankshafts in the K301. They just machined part of the counterweights off and drilled a few holes to bring it into balance with the lighter weight K301 piston assembly. And I have experienced certain K301 engines vibrate severely for some unknown reason. I had to have the crankshaft dynamically and precision spin-balanced and then the engine ran smooth with a lot less vibration. This goes to show that the technology for single cylinder engine balancing during the 1960's isn't like it is today.

K-series VS Magnum Crankshafts -

A K-series K301 crankshaft cannot be used with a K321, K341 or K361 piston/rings assembly without adding a lot of weight to the counterweights because the K301 crankshaft is balanced too light. The opposite would need to be done if a K321, K341 and K361 crankshaft is used with a K301 piston/rings assembly, or the engine would vibrate more than normal. If a K-series K301 crankshaft is going to be used in a K321, K341 or K361 piston assembly, it would need to precision spin-balanced.

The Magnum crankshafts are interchangeable with the older K-series crankshafts.... but the K301/M12, K321/M14 and K341/M16 Magnum crankshafts are all basically balanced the same... for a K301 piston/rings assembly. Some Magnum engines use three counterbalance gears. Just like the K-series, the two balance gears on the side of the block are to reduce the side-thrust of the counterweights of the crankshaft. But the lower balance gear in the Magnum is used to balance the rotating assembly because the Magnum counterweights are too light for the K321/M14 or K341/M16 piston/rings assemblies. Go here to learn how to align the three balance gears: Kohler Three Gear Balance Gear System Service Bulletin 208.pdf. (require Adobe Acrobat Reader and use Google Chrome web browser for a faster download of web sites with large files.)

For the heavier M14 and M16 Mahle piston/rings assemblies, the bottom balance gear simulates additional weight on the counterweights of the crankshaft so the engine will run with less vibration. If the Magnum balance gears are left out with any model, the engine will vibrate terribly! But if the balance gears are purposely left out, such as for high RPM operation, the rotating assembly would need to be precision balanced to reduce dangerous vibration. The older K-series engines will not vibrate more than it did before without balance gears installed.

And if a Magnum crankshaft is replaced with a K-series crankshaft, the Magnum balance gears shouldn't be used with the K-series crankshaft. If they are used, the engine may vibrate a lot.

If a Magnum (M12, M14 or M16) crankshaft require three balance gears, it can be used without the balance gears in a K-series block if it is precision spin-balanced to reduce the vibration (with the connecting rod and piston/rings assembly) on a crankshaft balancing machine.

And I have no idea why Kohler changed the crankshaft balancing with the Magnum single cylinder engines to a three gear balancing system. It make no sense at all to me. I mean, the way the older K-series engines was balanced worked great. But anyway, it'll be best to leave out the balance gears and have the rotating assembly (crankshaft, piston/rod assembly) dynamically and precision spin-balanced. By having this done, the engine, with no doubt, should run much smoother and possibly last longer.

The early K-series crankshafts have a 3/16" wide slotted [flywheel] keyway and a 5/8" diameter threaded stud w/nut to retain the flywheel, and the later K-series and all Magnum crankshafts have a #5 Woodruff [flywheel] keyway and a 3/8" bolt to retain the flywheel.

The K241/M10 crankshafts have a shorter stroke (2.875") than the K301, K321, K341 and K361 cranks (3.25"). The K241/M10 crankshafts are in a class by themselves. Therefore, they can't be used in combination with a K301, K321, K341 and K361 connecting rod or piston assembly without extensive machine work and precision balancing. And the K301, K321, K341 and K361 cranks can't be used with a K241 connecting rod or piston assembly without extensive machine work and precision balancing.

Identifying the Differences in the K-series Crankshafts -


Kohler's Dynamic Counterbalance System -

Kohler's Dynamic Balance SystemVarious Kohler engine models K241/M10, K301/M12, K321/M14, K341/M16 and K361 use a Dynamic Balance System, which are two out-of-balance gears that rotate on stub shafts that's pressed into the PTO side of the engine block. These counterbalance gears rotate in opposite direction of the crankshaft. These gears reduce the rotating side thrust (vibrating affect) of the crankshaft. Most K241 and M10 engines came from Kohler without balance gears. Only four K241 engines came from Kohler with balance gears installed. These engines have the specification number: 46578, 46590, 46593 & 46718. And only four M10 engines came from Kohler with balance gears installed. These engines have the specification number: 461509, 461513, 461526 and 461534. All other specification numbers for the K241 and M10 engines have no balance gears. However, if your engine vibrates a lot, it should to be precision spin-balanced. But most K241 and M10 engines (without balance gears) run smooth from the factory.

Unless a heavier crankshaft is used (than the original one that came in the engine), in some K241 Kohler engines, it will vibrate more if the balance gears are left out. But the K301, K321, K341 and K361 engines won't vibrate much more without the balance gears. And the balance gears in the K241 engine are the same as the ones used in the K301/M12, K321/M14, K341/M16 and K361 engines. They have the same OEM Kohler part number.

For reasons unknown why Kohler did this, some K301 Kohler engines will vibrate more without balance gears, while others don't vibrate much more without the balance gears. The counterweights on the crankshafts that vibrate more and the ones that don't vibrate as much look almost the same, too. Only the K301 engines experience this. Most K321, K341 or K361 engines don't vibrate much more without balance gears. Anyway, if the balance gears have been removed from a K301 engine, and it vibrates more than before, then the Crankshaft Balance Plate Kit from Kirk Engines http://www.kirkengines.com/index.php#CrankshaftBalancePlateKit can be installed, or have the rotating parts (crankshaft and rod/piston assembly) precision spin-balanced at an automotive speed shop. (A place that balance race car engines.)

For most single cylinder Kohler engines, balance gears isn't necessary.

Leaving out the balance gears shouldn't have a noticeable effect on engine vibration, but sometimes they help to reduce engine vibration. So if you choose to reinstall or leave them in an engine that will never turn more than 4,000 RPM (this is the maximum RPM for pulling in stock classes or for general lawn and garden use), make sure that the bearings in the [balance] gears and the stub shafts that they spin on are in good condition. If the bearings are worn and if the balance gears wobble, they'll wear the crankshaft gear teeth and they could break, possibly destroying the engine. By the way - the balance gears alignment tool (timing gage) is no longer available from Kohler. If you find a good used one or a new one from a Kohler dealer's old stock, the Kohler part numbers are 25 455 06-S, 10355 or Y-357. It's much easier to use this plastic tool when aligning the balance gears in time with the crankshaft. See the animated image to the right for correct identification of this tool.

Once, just for curiosity, after I've rebuilt a K301 Kohler engine, I've ran the engine with the balance gears installed and correctly aligned with the crankshaft. Then I removed the balance gears just to see if the engine would vibrate more. (It wasn't a lot of work to remove the gears. I removed the oil pan, snap rings, washers and spacers, rotated the crankshaft to clear the balance gears, and lifted the gears right out.) Anyway, I found that without the balance gears, the engine vibrated EXACTLY the same as when the balance gears were installed! Wonder why Kohler installed them in the first place. ????

Counterbalance gears does no good to install them. Most Kohler engines don't come with them and they do very little to help reduce engine vibration. When left out, the engine will not vibrate more than usual. Besides, being balance gears are made of cast iron and operate out of balance on a single needle bearing, they've been known to break and destroy the crankshaft, cam and engine block. I've seen this happen a few times. Therefore, I highly recommend leaving them out.

By the way - I've seen balance gears in the K241, K301, K321, K341 and K361 engines, but not every one of these engines have balance gears. I've even seen some Kohler Magnum M16 engines have three balance gears! Anyway, it seems that Kohler was selective in which engines they put them in. Perhaps they only put them in engines that was installed in a "luxury-type" of garden tractor to help reduce operator discomfort. And every balance gear I've ever seen appear to be exactly the same weight and design.

If a stock OEM-type piston assembly and connecting rod is going to be (re)used, there's no need to re-balance the crankshaft/piston/rod assembly if these gears are removed. If you want, leave the balance gears out. Actually, they're more trouble reinstalling and align with the crankshaft than they're worth. You won't notice that much difference in the vibration of the engine, either. It won't damage anything and it won't hurt anything. The engine will operate just fine without them.

The balance gears in a Kohler engine can be removed without removing the crankshaft. Use quality-made heavy duty snap ring pliers with 90° tips to remove the [heavy gauge] snap rings that retain the balance gears. Because these snap rings are actually thicker than ordinary ones which makes them harder to expand. A flat screwdriver may need to be wedged under each snap ring to help them off the stub shafts. (Been there, done that many times. And it's difficult each time.) Be sure to remove the spacers (if equipped) and shims from the shafts, too. The counterweights on the K301 crankshaft are machined off, allowing room to remove the balance gears. But on a K321, K341 and K361 engine, one of the counterweights on the crankshaft may be in the way. If it is, try driving the pins into the crankcase from outside the PTO end of the block. By the way - the shims from removal of the balance gears can be used as camshaft shims to set the cam-to-block clearance on the K241-K361 engines.

Don't (re)install the balance gears in an engine if it's going to turn above 4,000 RPM! (The factory maximum RPM for virtually all small gas engines, including all of Kohler engines is 3,600.) The high RPM or wide open throttle operation could cause them to break and destroy the engine! So when building an engine that's going to turn above 4,000 RPM, these gears (and spacers) MUST be permanently removed! Remember - "An ounce of prevention is worth a pound of cure." It's okay to leave the stub shafts in the block. Or if you want, the balance gear stub shafts can be removed with a hardened 7/16" steel rod and a big hammer to drive them out from the PTO end of the block. They will fall into the block. And don't worry about driving out the stub shafts with a hammer, the engine block will not crack. But using a hydraulic press to drive the pins out could cause the block to crack.

The best and easiest way to plug the stub shaft holes is to cut 3/8" NPT threads into the holes from outside the block, and then install a couple of 3/8" NPT Hex Socket (Allen) pipe plugs. A special tool is required to install 1/2" cup-shaped expansion plugs in the stub shaft holes. And be sure to use RTV silicone sealant with either plug to prevent an oil leak, too.


How To Remove the Crankshaft from a Kohler Engine -

Remove the piston/connecting rod, flywheel, bearing plate and anything that's on the PTO end of the crankshaft. (Not necessarily in this order.) Then very gently, bump the PTO end with a wooden block to remove the crankshaft from the block. And there's no need to reinstall the balance gears. They serve very little purpose.


FYI - A cast iron flywheel with a broken off fin (fan blade) will definitely run out of balance, and cause the entire engine to vibrate badly. At higher RPMs (up to 4,000 RPM), the severe vibration could also cause the sheet metal to crack at the mounting bolt holes, and in rare cases, possibly cause the crankshaft to break at the rod journal. To statically (not spinning or in motion; at rest) put the flywheel back in balance, if the entire fin is broken off, simply break off the fin directly opposite of the broken fin with a hammer. But if only part of the fin is chipped off, use an angled hand grinder or a reciprocating saw / saw saw to remove about the same amount of chipped off material from the opposite fin. Try to make the fins match each other to maintain proper balance. The flywheel should still be safe to use, and the remaining intact fins will provide plenty of fresh air to adequately cool the engine. But the best way to put the flywheel 100% back in balance is to have it dynamically precision spin-balanced with an automotive crankshaft/flywheel balancing machine.


How Fast Can You Spin A Cast Iron Crankshaft?

As long as the piston assembly and connecting rod to the crankshaft counterweights, including the flywheel, starter pulley and clutch components are all precision balanced, you can spin it as fast as you want. Just make sure to have the crankshaft checked for stress cracks (magnafluxed) before using it.


When installing a high-performance [heavier than OEM stock] piston and connecting rod assembly in a single cylinder engine, and to minimize dangerous vibration and to prevent the possibility of self destruction, the crankshaft must be re-balanced (more weight added to the counterweights) to compensate for the difference in weight. If an engine vibrates severely, then the only things that causes the vibration is the piston/rings/wrist pin/clips assembly and/or the connecting rod isn't equally balanced to the crankshaft's counterweights. Another thing would be an out of balance flywheel. Also, if there's a parasitic accessory attached to the crankshaft, such as a bent pulley, it could be causing the vibration.

Note: when using an OEM piston assembly and connecting rod, and if the rod journal (crank pin) on the crankshaft is reground for a smaller diameter bearing, that will not throw off the balance of the rotating assembly. Because the undersized rod bearing will take up the material that was removed from the crankshaft.

FYI - STATIC balancing is when parts are at rest, and DYNAMIC balancing is when parts are in motion. Dynamic balancing is a more precise way to balance anything that spins, but static balancing is a lower cost alternative... also proven very effective. An accurate and precision electronic digital scale that breaks at 1/10th of an ounce (0.1 lb.) or 1 gram to static balance a crankshaft to the piston and connecting rod assembly will be needed. For an example of how much 1/10th of an ounce is, a dime (10¢) weighs exactly 1/10th of an ounce (2.8 grams). But with a single cylinder engine, the engine will still vibrate some due to the side thrust of the counterweights, which is unpreventable.

How to Static Balance a Single Cylinder Engine:

  1. Precision Electronic Digital ScaleAcquire a precision electronic digital scale that can weigh up to around 13 lbs., and one that breaks at 1/10th of an ounce (0.1 lb.) or 1 gram. An accurate and precision balance beam scale can be used to weigh the differences between the stock piston/rod assembly and the high performance piston/rod assembly. An electronic digital scale is more precise for balancing an engine than a mechanical one. But the higher the capacity of an electronic digital scale, the less precise it will be.
  2. Use pencil, paper and arithmetic for this procedure, to make a note of the results. Pencil and Paper
  3. Weigh the stock (preferably std size) piston, rings, pin, clips and connecting rod as a unit. Make a note of the total weight. Be sure the scale is on a flat, level surface. If it's not, an inaccurate reading will result. Weigh the piston, rings, wrist pin, clips and connecting rod that originally came with the crankshaft. If you don't have the original piston/rod assembly, here's the approximate weights for them: The OEM stock K301 piston assembly and rod weighs 29.1 ounces or 823 grams. And the stock OEM K321, K341 and K361 piston assembly and rods weighs 31.4 ounces or 891 grams.
  4. Now weigh the high-performance/aftermarket piston, rings, pin, clips, connecting rod and bearing insert as a unit. Make a note of that weight.
  5. Subtract the two above È weights and make a note of the difference.
  6. Now weigh the crankshaft that was originally used with the stock OEM piston/rod assembly. Make a note of that weight. The average weight of a typical cast iron Kohler K301 crankshaft with a 1" diameter x 3" long PTO end is 151 oz. or 4,280 grams. And the average weight of a typical K321, K341 and K361 crankshaft with a 1-1/8" diameter x 3" long PTO end is 158.2 oz. or 4,485 grams. Remember that the weight of every crankshaft will vary a few ounces depending on the length and diameter of the PTO end, if the PTO end has a drilled and threaded bolt hole, or if the flywheel end has a 3/8" threaded bolt hole or a 5/8" or 3/4" diameter stud. (These numbers are for reference only.)
  7. Add the difference in weight of the two piston/rod assemblies above È to the crankshaft counterweights. To add weight to the crankshaft, fill in the factory drilled holes with lead capped with steel that's held in place with a roll pin driven in crossways; bolt or weld an 1/8"± curved plate steel on the side of the counterweight next to the gear (make sure the balance plate and/or bolts clears the compression release mechanism on the camshaft, if equipped); or if the crankshaft needs a lot of weight, drill holes through the counterweight(s) and install tungsten steel (heaviest metal available) secured in place with beads of welding. Try to add an equal amount of weight to each counterweight so the crankshaft won't it be too heavy on either end. Not doing this may result in crankshaft breakage over time. And remember, crankshaft breakage could destroy other internal parts of an engine as well!

    It must be a high-quality welding job whenever any welding is done on a cast iron crankshaft! Remember, cast iron is porous and absorbs oil. This means the counterweights must be thoroughly heated with an acetylene torch or the crank placed in a special oven furnace and rotated it against large flames to burn the oil out of the metal, then it'll be good for welding.
  8. Weigh the crankshaft again and subtract the difference from the result that was derived in step 4.
  9. The added weight to the crankshaft should now reflect the difference in weight of the two piston/rod assemblies. If it doesn't, it's OK to grind off some weight from the counterweights.
  10. That's it! The crankshaft and piston/connecting rod assembly are now statically balanced. On the average, about 160 grams or 5.64 ounces of weight is added to the counterweights on a Kohler crankshaft to precision balance it for a stock connecting rod and piston/rings assembly.

If a high-performance K301 piston assembly is going to be used in a Kohler engine, a K321, K341 or K361 crankshaft can be used instead for rebalancing. Less weight will need to be added to the counterweights because of the smaller and lighter weight K301 piston assembly.

By the way - Actually, it's best to have the rotating assembly precision and dynamically spin-balanced with a crankshaft balancing machine. Because just bolting on a weight to side of one of the counterweights without spinning the crankshaft to check the balance against it and the rod and piston assembly may add too much weight or not enough and the engine might still vibrate a lot. I've seen this happen several times.

Heavy metal (tungsten steel) and tools that's specifically made for crankshaft balancing can be purchased from GOODSON (http://www.goodson.com) Tools and Supplies for Engine Builders. (Request a catalog from them.)

The reason most [high dollar] billet steel crankshafts break at wide open throttle is because they were not dynamically and precision spin-balanced using a specialized crankshaft/flywheel balancing machine. This happens when the counterweights on the crankshaft weighs much more than the piston and connecting rod assembly. When out-of-balance, the crankshaft flexes a few thousandths of an inch at high RPMs, which weakens the metal and causes fatigue cracks, eventually resulting in breakage. When a crankshaft breaks, it can destroy the camshaft and possibly the engine block. So it's very important that an aftermarket billet steel (and cast iron) crankshaft be dynamically and precision spin-balanced when the engine is ran at very high RPMs. Most manufacturers of billet steel crankshafts do not dynamically and precision spin-balance them. They include counterweights on the crankshaft that's pre-weighed and matched to the weight of the piston and connecting rod assembly to be used with the crankshaft. The counterweights must weigh the same as the piston and connecting rod assembly, with the exception of the weight of the rod journal, which counter-weighs the counterweights. When rotating, the rod journal too, adds weight to the piston and connecting rod assembly. And the same balancing machine that's designed to balance automotive crankshafts and flywheels can be used to balance single cylinder Kohler (and other makes of small engines) crankshafts and flywheels. To balance a crankshaft with a specialized flywheel/crankshaft balancing machine, all that is needed is a bob-weight that clamps on the rod journal. The bob-weight simulates the weight of (and must weigh exactly the same as) the piston and connecting rod assembly that is going to be used with the crankshaft to be balanced. If the piston and connecting rod assembly and/or crankshaft is used with another piston and connecting rod assembly and/or crankshaft, the rotating assembly will be out-of-balance.

But then again, when excessively out of balance, a billet steel crankshaft will not always break. A billet connecting rod will break instead. This happens when the piston and rod assembly weighs much more than the counterweights on the crankshaft. What happens is, as the engine rotates at high RPMs or at wide open throttle, the weight of the piston and connecting rod is sent upward a lot more than the counterweights are sent downward , resulting in two unequal opposing forces, and this places severe strain on the connecting rod cap' bolts. Eventually, the upward force of the piston and rod will cause the bolts to stretch (the 4-bolt hex socket (Allen) head cap screws (bolts) in certain billet rods are more prone to stretching), which will cause the rod to knock, and the continuing stretching of the bolts will cause them to break, ultimately resulting in connecting rod breakage, which can destroy the entire engine block. So it'll be a good idea to definitely spend the extra time and money to have your rotating assembly dynamically and precision spin-balanced.

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.

If the engine still vibrates at high RPM or at wide open throttle after doing the above È, it's either because of the side thrust of the crankshaft counterweights (which is normal in single cylinder engines), or if the vibration is severe, have the flywheel checked for precision balance and/or the clutch assembly trued up in a metal lathe. If you have a garden tractor with rubber motor mounts, these must replaced with solid metal mounts. If the crankshaft/piston/rod are balanced correctly and the flywheel is also balanced, and the tapers are clean, the crankshaft should last the life of the engine. Even when used in high-performance conditions.

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High Quality Inductive Wireless Handheld Small Engine Tachometer. A tachometer helps in setting the correct RPMs of an engine to prevent from over-revving and possible damage to the engine. For gas/spark ignite engines only. Works with magneto and battery-powered ignition systems. High quality and very accurate. This handheld analog tach works great for checking/setting the RPM on various small engines in the shop, and/or for checking/setting the RPM [tech] on stock governored competition pulling engines. Hold sensor (antenna) close to spark plug wire for reading. Operates off a self-contained replaceable 9 volt battery. Has built-in battery voltage check. Reads up to 5,000 RPM on the low scale, and 15,000 RPM on the high scale.
  • $85.00 each, plus shipping & handling.
High Quality Inductive Small Engine Tachometer/Hour Meter. A tachometer is required in setting the correct RPMs (normally 3,200 or 3,600 maximum for small engines) of an engine to prevent over-revving and possible damage to the engine or dangerous flywheel explosion. Very accurate. Can be hand-held to temporarily set engine RPM or permanently mounted to monitor engine RPM at all times. Large 3/8 inch LCD display. Works with all spark ignition engines by selecting engine type using S1 and S2 buttons. Works with magneto and battery-powered ignition systems. If tachometer does not turn on automatically as soon as engine starts, press and hold the two buttons at the same time. Instructions included. Tachometer reads up to 99,999 RPM. Hour meter reads up to 9999:59 hours/minutes then resets to Zero. Programmable maintenance hour setting with service icon, a reminder when to change oil or other service. Can be manually reset to Zero hours. Programmable maintenance hour setting with service icon, a reminder when to change oil or other service. Easy installation: Single wire wraps around spark plug wire and secured with two supplied nylon zip-ties. No wire terminal connections required. Tachometer can be surface-mounted and secured with two screws. Has built-in battery rated up to 4 years. Sealed unit; weather and water resistant. Dimensions: 2" wide x 1-3/4" depth x 3/4" height.
  • $20.00 each, plus shipping & handling.
High Quality Digital Tachometer/Proximity Sensor Kits. A tachometer is required in setting the correct RPMs (normally 3,200 or 3,600 maximum for small engines) of an engine to prevent from over-revving and possible damage to the engine or dangerous flywheel explosion. Will work with single- or twin-cylinder small engines or multi-cylinder automotive engines, gas or diesel. Works with magneto (with a battery to power the proximity sensor and tachometer) and battery-powered ignition systems. Very accurate. Can be used for lawn & garden equipment or competition pulling engines. Designed to be permanently mounted to monitor engine RPM at all times. This precision digital tachometer operates with external power and on the same principle as my crank- or flywheel-trigger ignition systems with a proximity sensor to detect a target, which can be a small ferrous steel screw or pin, or magnet in a rotating disc on the crankshaft or on/in flywheel. Cannot be wired in conjunction with the Dynatek Dyna S or PerTronix Ignitor ignition modules. It must be wired separately or can be used with any of my crank trigger ignition systems that also use a proximity sensor. A sturdy steel or aluminum bracket will need to be fabricated by customer to mount the sensor in close proximity of the detector/trigger target. Set air gap/clearance at .010"-.188". Tachometer works with 8-24 volts DC, proximity sensors works with 6-36 volts DC. Tachometer can be in-dash or panel-mounted. Dimensions for mounting hole: 3" wide x 1-17/32" wide. Tachometer measures 1" in depth. Tachometer works with 8-24 volts DC, proximity sensors works with 6-36 volts DC. Dimensions of each proximity sensor below: 15/32" (12mm) diameter x 1-3/8" thread length. Some proximity sensors have an LED (Light Emitting Diode) on the rear of unit. If the proximity sensor is wired incorrectly, the LED will stay on and go off when activated. Displays up to 9,999 RPM. Very accurate. Tachometer returns to zero [0000] when power (ignition) is turned off. Wiring Instructions: #1 wire on tachometer connects to brown wire on (either) proximity sensor and ignition switch (12 volt power), #2 wire on tachometer connects to blue wire on (either) proximity sensor and engine/chassis ground (battery negative (–) post), and #5 wire on tachometer connects to black wire on (either) proximity sensor. Wires #3 and #4 connects to nothing. Wiring can also be integrated with crank trigger ignition with a proximity sensor. Choice of RED or BLUE numeric display.
  • Tachometer only. Can be used with virtually any Normally Open 3-wire hall effect, inductive or cube-shaped proximity sensor. $12.00 each, plus shipping & handling.
  • Complete Kit with Tachometer and 15/32" Diameter x 2-1/2" Length x 43" Cable Length Hall Effect Proximity Sensor. (Senses the South pole of a small magnet embedded in an aluminum rotating locking collar, disc, or OEM magnet embedded in a flywheel.) $22.00 each, plus shipping & handling.
    • Aluminum Locking Collar w/Embedded Rare Earth Magnet and Allen Set Screw. Please specify diameter of crankshaft PTO end for locking collar w/embedded rare earth magnet. Most common crankshaft PTO end diameters are 1" and 1-1/8", but 3/4", 1-1/4", 1-3/8", 1-7/16" and 1-1/2" are rare. Most billet steel crankshafts have a 1-1/2" diameter PTO end (raised shoulder). Other sizes available. $15.00 each, plus shipping & handling.
  • Complete Kit with Tachometer and 15/32" Diameter x 2-1/2" Length x 43" Cable Length Inductive Proximity Sensor. (Senses the head of a small steel screw in a rotating locking collar, disc or flywheel.) $25.00 each, plus shipping & handling. [Return to previous section]
Solid Motor Mounts for Cub Cadet "Quiet Line" Tractors - Replace Deteriorated "ISO" Rubber Motor Mounts with a Set of Machined Solid Steel Motor Mounts! An original, ingenious, innovative concept invention by Brian Miller, because I was the one who originally thought of, promoted and advertised the use of this product. Please accept no copycat products of this kind.

Details include:

  • These install between the engine mounting cradle and tractor frame. They are an alternative to replacing deteriorated OEM "ISO" rubber engine mounts, which is usually associated with damaged clutch components. Fits Cub Cadet "Quiet Line" models 482, 680, 800, 1000, 1100, 1200, 1204, 1210, 1211, 1250, 1282, 1340, 1450 and 1650. If your tractor has two angled brackets that the engine is mounted on with rubber mounts between the brackets and the tractor frame, then these are what your tractor needs.
  • For competition pulling, heavy towing, pushing snow or general lawn and garden use. A MUST for competition pulling or everyday use because these solid mounts stabilize the engine (and clutch assembly) to prevent severe engine vibration at high RPM or at wide open throttle, which can destroy the clutch disc and driveshaft components, especially with the flexible 3-pin clutch drive plate.
  • Direct replacement with no modifications to the tractor whatsoever. Replaces entire OEM ISO rubber mounts. These install between the tractor frame and engine mounting brackets. A thick flat washer fastens on top of the brackets with the solid mounts between the brackets and tractor frame. Precision machined so they set the engine height at the correct alignment with the driveshaft.
  • By the way - rubber motor mounts are intended for operator comfort from engine vibration only. The ISO-mount tractors with solid motor mounts installed would feel and operate just like the tractors with a solid mounted engine. And some people who installed my solid motor mounts just to mow grass tell me that the mounts don't cause their tractor to vibrate much at all. But others have installed them and said the vibration is unbearable. The engine is obviously not precision spin-balanced because the old Kohlers was machined and balanced in the 1960's-70's with old technology. In this case, the engine should be dynamically and precision spin-balanced. So all I can say is try these solid mounts, and if you don't like them, return them for a full refund, less shipping & handling. Or to minimize the vibration, either have the rotating engine parts dynamically and precision spin-balanced, or install a set of rubber mounts. And the welded enforcement cross bar is required only with rubber ISO mounts. It is not required with solid motor mounts.
  • Can be easily removed if rubber mounts are used instead. If you'd prefer to use new rubber motor mounts, you can install an OEM Cub Cadet ISO mount kit, part # 759-3952, or visit your nearest NAPA auto parts store. They have a variety of rubber mounts. Some shock absorber mounts are the same thing.
  • Weighs about 4 ounces each.


Solid Motor Mounts for Wheel Horse - Replace Deteriorated ISO-Mounts with a Set of Machined Solid Aluminum Motor Mounts! An innovative concept invented by Brian Miller, because nobody else advertise and offer this product for sale. Please accept no other advertised copycat products of this kind.

Details include:

  • An alternative to the deteriorated OEM rubber ISO mounts or for competition pulling. A MUST for competition pulling because they stabilize the engine to prevent severe engine vibration at high RPM or wide open throttle. Fits Wheel Horse models C-81, C-85, C-101, C-105, C-121, C-125, C-145, C-165, C-175 and 512-D.
  • For competition pulling, heavy towing, pushing snow or general lawn and garden use.
  • Direct replacement - replaces the entire rubber mounts. Machined so they set the engine the same height as the OEM rubber mounts. Fastens to engine cradle with included 1/4" grade 8 bolts and locknuts. Reuse OEM center bolt.
  • By the way - rubber motor mounts are intended for operator comfort from engine vibration only. The ISO-mount tractors with solid motor mounts installed would feel and operate just like the tractors with a solid mounted engine. And some people who installed my solid motor mounts just to mow grass tell me that the mounts don't cause their tractor to vibrate much at all. But others have installed them and said the vibration is unbearable. The engine is obviously not precision spin-balanced because the old Kohlers was machined in the 1960's-70's with old balancing technology. In this case, the engine should be dynamically and precision spin-balanced. So all I can say is try these solid mounts, and if you don't like them, return them for a full refund, less shipping & handling. Or to minimize the vibration, either have the rotating engine parts dynamically and precision spin-balanced, or install a set of rubber mounts.
  • Can be easily removed if rubber ISO mounts are desired instead. If you'd prefer to use rubber motor mounts, the Wheel Horse part number is 108309.
    • Solid mounts with wide, thick flat washers and mounting hardware. $40.00 per set of four plus shipping & handling.
Used 9-1/2" diameter genuine OEM cast iron flywheel for Kohler K-series K241-K361 engines. These flywheels are for battery ignition only, not magneto ignition. They're in excellent condition and unaltered. No crack in the keyway, no broken or missing fan blades and no cracked or missing internal magnets for charging system (if used for general lawn and garden use). These flywheels are for stock tractors only; not to be turned above 4,000 RPM!
  • Flywheel with ring gear and internal charging magnets. $125.00 each, shipping included within in the Continental U.S. if purchased separately.
  • Flywheel without ring gear (install your own ring gear) and with or without internal charging magnets. $85.00 each, shipping included within in the Continental U.S. if purchased separately.
  • Flywheel without ring gear (install your own ring gear) and majority of fan blades removed and precision balanced and with or without internal charging magnets. $115.00 each, shipping included within in the Continental U.S. if purchased separately. (Click on picture to the right for a larger view.)
  • Flywheel with ring gear and majority of fan blades removed and precision balanced and with or without internal charging magnets. $135.00 each, shipping included within in the Continental U.S. if purchased separately. (Click picture below for a larger view.)
  • Used ring gear. $25.00 each, plus shipping & handling.
  • Your flywheel - remove majority of fan blades and precision rebalance. $85.00 labor, return shipping extra. Includes cutting most of the fan blades off, chuck it in our lathe to true up the fan blades so they're all even and then balancing it.

Dynamic Precision Spin-Balancing Service -

Balance (cast or steel) flywheel for Kohler K241-K361 engines. $60.00 each labor, plus return shipping & handling.

Balance cast iron (Kohler) crankshaft and matching connecting rod and piston assembly. $200.00 per rotating assembly, plus return shipping & handling. NOTE: I will need to take your parts to the only reputable and trusted automotive machine shop in central Missouri (Jefferson City) that does professional engine balancing. Or you can contact Precision Machine, Inc. (PMI) to have your rotating assembly precision spin-balanced. They are located at 1703 Christy Drive, Jefferson City, MO 65101. Phone: 573-635-7214. Return To Previous Paragraph or Section

Flywheel Retaining NutFlywheel Retaining Nuts for threaded stud on end of K-series and steel crankshafts. IMPORTANT: Apply thin coat of motor oil on threads of crankshaft before installing nut then torque each at 65 ft. lbs.
  • Plain Nut. 5/8-18 UNF threads. Apply medium strength liquid threadlocker on threads to prevent flywheel from possibly loosening. Replaces Kohler part #'s 25 100 02-S, X-119-14. (Discontinued from Kohler.) $1.00 each, plus shipping & handling.
  • OEM-Type Castle/Tapered Seat Self-Locking Nut. 5/8" diameter, fine thread (5/8-18 UNF). A-1 Miller part. Replaces Kohler part #'s 25 100 02-S, X-119-14. (Discontinued from Kohler.) $1.50 each, plus shipping & handling.
  • All-Metal Self-Locking Nut. 5/8" diameter, fine thread (5/8-18 UNF). Replaces Kohler part #'s 25 100 02-S, X-119-14. (Discontinued from Kohler.) $1.50 each, plus shipping & handling.
  • Plain Nut. 3/4-16 UNF threads. Apply medium strength liquid threadlocker on threads to prevent flywheel from possibly loosening. Replaces Kohler part #'s X-89-11, X-119-16. (Discontinued from Kohler.) $1.00 each, plus shipping & handling.
  • OEM-Type Castle/Tapered Seat Self-Locking Nut. 3/4" diameter, fine thread (3/4-16 UNF). A-1 Miller part. Replaces Kohler part #'s X-89-11, X-119-16. (Discontinued from Kohler.) $1.75 each, plus shipping & handling.
  • All-Metal Self-Locking Nut. 3/4" diameter, fine thread (3/4-16 UNF). Replaces Kohler part #'s X-89-11, X-119-16. (Discontinued from Kohler.) $1.75 each, plus shipping & handling.
Flywheel retaining bolt for threaded hole in end of crankshaft. Each are grade 8, 1-1/2" thread length. Torque at 40 ft. lb. Replaces Kohler part # 25 086 253-S.
  • 3/8" diameter, fine thread (3/8-24 UNF). $1.00 each, plus shipping & handling.

Flat washer for retaining flywheel or aluminum clutch hub to flywheelFlywheel / Aluminum Hub Retaining Washers. A thick, wide washer is a must to secure flywheel and prevent clutch/driveshaft aluminum hub adapter breakage! Each made of steel and measures 1-1/4" o.d. x approximately 1/4" thick.

  • Washer w/13/32" hole. Must be used with aluminum hub that has a 3/8" hole.
    • A-1 Miller part. $3.00 each, plus shipping & handling.
    • OEM Kohler part # 12 468 03-S. $3.40 each, plus shipping & handling.
  • Washer w/5/8" hole. To be used with aluminum hub that has a 5/8" hole. A-1 Miller part. (Discontinued from Kohler.) Replaces Kohler part # X-25-104. $3.50 each, plus shipping & handling.
  • Washer w/3/4" hole. To be used with aluminum hub that has a 3/4" hole. A-1 Miller part. (Discontinued from Kohler.) Replaces Kohler part # X-25-71. $3.50 each, plus shipping & handling.
Steel Adapter Step Washers for Centering OEM Cub Cadet or billet aluminum clutch hubs on crankshaft. A must to prevent severe wobble and prevent hub and driveshaft/clutch breakage! NOTE: As long as the rotating clutch components are trued-up in a metal lathe to minimize vibration, and the wide, thick washer is used inside the hub to secure the hub to the flywheel, and the flywheel retaining nut or bolt properly torqued, the OEM cast aluminum clutch hub have been proven to hold up to a wide open throttle pulling engine.
  • Spacer/Bushing. Use with 3/8" washer above È. Dimensions: 3/8" i.d. x 5/8" o.d. x 3/8" height. OEM Kohler part # 47 158 05-S. $1.65 each, plus shipping & handling.
  • Step Washer. Dimensions: 3/8" i.d. x 5/8" o.d. x 1-1/4" o.d. x 1/2" overall height. $9.00 each, plus shipping & handling.
  • Step Washer. Dimensions: 5/8" i.d. x 3/4" o.d. x 1-1/4" o.d. x 1/2" overall height. $9.00 each, plus shipping & handling.
OEM Kohler Aluminum Clutch Hub Adapters. Fits John Deere and all models of Cub Cadet garden tractors.
  • Hub adapter w/5/8" hole and pulley. Used and in excellent condition. No longer available from Kohler. OEM Kohler part # 41 071 01. $40.00 each, plus shipping & handling.
  • Hub adapter w/3/8" hole. Used and in excellent condition. No longer available from Kohler. OEM Kohler part # 52 071 02-S. $40.00 each, plus shipping & handling.
  • Hub adapter w/5/8" hole. Used and in excellent condition. $40.00 each, plus shipping & handling.
  • Hub adapter w/5/8" hole. New. OEM Kohler part # 41 071 03-S. $88.10 each, plus shipping & handling.
New main crankshaft bearings for Kohler K-series and Magnum engine models K141, K160/K161 and K181/M8. These are specifically designed to provide maximum performance by means of precise ball implement selection. Heat treated. 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. Part # 150-960. $10.00 each, plus shipping & handling.
New 8 ball main crankshaft bearings for Kohler K-series and Magnum engine models K241/M10, K301/M12, K321/M14, K341/M16 and K361. These are specifically designed to provide maximum performance through precise ball implement selection. At high RPM or at wide open throttle, bigger balls run cooler which create less rolling resistance than bearings with smaller balls. Heat treated. Made in China, but has the same quality as OEM Kohler bearings for long wear. Dimensions: 1.57" i.d. x 3.54" o.d. x .90" width. Part #150-973. $15.00 each, plus shipping & handling.
NOTE: If you cleaned all the oil out of the crankshaft main [ball] bearings and allowed them to dry, and when 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 then spin them. They should be a lot quieter. The same thing will happen with new ball bearings.


Second Half of Balancing a Single Cylinder Engine to Reduce Dangerous Vibration | [Top of Page]


Important Information About Small Engine Flywheels

Where Science and Common Sense Come Together for Safety and Better Engine Performance
Please visit these other Brian Miller's websites: A-1 Miller's Performance Enterprises - Parts & Services Online Catalog | Hot Rod Garden Tractor and Mini-Truck Pullers Association



First of all, the flywheels on Kohler K-series and Magnum engine models K241/M10, K301/M12, K321/M14, K341/M16 and K361 will interchange, because the tapers and keyway widths are the same. The only difference is the type of starter and ignition system used. Some engines with a rope starter have magneto ignition and a 9-1/2" flywheel with no ring gear; other engines with a starter/generator and battery ignition, use either a 8" or 9-1/2" flywheel with no gear ring; some early engines with magneto ignition have a 9-1/2" flywheel with no ring gear; while most later K-series engines have battery ignition, and a 9-1/2" ring gear flywheel with internal magnets for an alternator charging system. Also, all Kohler Magnum M10-M16 engines use the same flywheel. The Kohler KT-series twin cylinder flathead engine models KT17, KT17 series 2, KT19, KT19 series 2 and KT21 (which is a snowmobile engine) use the same flywheel. And the Kohler Magnum twin cylinder flathead engine models M18 and M20 use the same flywheel.

Four types of flywheels were used on the K241-K361 K-series Kohler engines. They are as follows:

  1. From 1960 to 1973, many of the K241 and K301 engines came with an 8" diameter flywheel. The engine had battery-powered ignition, and a starter/generator provided the cranking source to start the engine and then it produced the power source to recharge the battery and power any electrical accessories. These were popular with the narrow- and wide-frame (with solid-mounted engine) IH Cub Cadets.
  2. Very few of the early K241 and K301 engines came with a 9-1/2" diameter flywheel with an unmachined edge for a starter ring gear, and there's no way to install a ring gear. These engines had a magneto ignition system. There's two magnets attached to inside the flywheel, the ignition coil is fastened on a stator to the bearing plate and a rope was used on a large notched pulley that's attached to the flywheel to crank the engine. There is no battery and no charging system involved. These were used on self-contained, stand-alone engine units, such as truck-mounted air compressors, generator/welders, water pumps, etc., and they were popular with the U.S. Military because there was no recoil starter and very few ignition parts to give trouble. Certain ignition coils are no longer available from Kohler for these engines.
  3. Another 9-1/2" diameter flywheel with an unmachined edge for a starter ring gear was also used on very few of the early K241 and K301 engines. There's no magnets inside the flywheel and no [magneto] stator. The engine had battery-powered ignition, and a starter/generator provided the cranking source to start the engine and then it produced the power source to recharge the battery and power any electrical accessories. These are popular with certain models of Case garden tractors.
  4. In 1974, the K241-K361 engines came with a 9-1/2" diameter flywheel with a machined edge for a starter ring gear and a ring of magnets on the inside. The engine had battery-powered ignition, and a small, gear type starter motor cranks the engine to start it and an alternator charging system produced the power source to recharge the battery and power any electrical accessories. These were popular with the wide-frame "Quiet Line" IH-built Cub Cadets and certain spread-frame MTD-built Cub Cadets.

And the K-series and Magnum flywheels have the same overall dimensions. The only difference is, the K-series flywheel has integrated fins (fan blades) and the Magnum flywheel use a bolt-on plastic fan blade unit, and it has an integrated magnet for the solid state ignition. The starter ring gear will also interchange between the two flywheels. As a matter of fact, the same ring gear fits the K241/M10-K341/M16 and K361 K-series and Magnum single cylinder engines, and the KT-series and Magnum twin cylinder engines.

FYI - A cast iron flywheel with a broken off fin (fan blade) will definitely run out of balance, and cause the entire engine to vibrate badly. At higher RPMs (up to 4,000 RPM), the severe vibration could also cause the sheet metal to crack at the mounting bolt holes, and in rare cases, possibly cause the crankshaft to break at the rod journal. To statically (not spinning or in motion; at rest) put the flywheel back in balance, if the entire fin is broken off, simply break off the fin directly opposite of the broken fin with a hammer. But if only part of the fin is chipped off, use an angled hand grinder or a reciprocating saw / saw saw to remove about the same amount of chipped off material from the opposite fin. Try to make the fins match each other to maintain proper balance. The flywheel should still be safe to use, and the remaining intact fins will provide plenty of fresh air to adequately cool the engine. But the best way to put the flywheel 100% back in balance is to have it dynamically precision spin-balanced with an automotive crankshaft/flywheel balancing machine.


The Safe and Correct Way to Remove a Small Engine Flywheel -

(Added 5/16/18) On a Kohler K-series engine with a 5/8" threaded crankshaft stud and with a starter/generator that comes in an IH-built Cub Cadet garden tractor, sometimes the aluminum clutch hub adapter that's mounted in front of the flywheel can be very stubborn to remove. This part must be removed before the flywheel shroud can be removed. So to safely remove the hub without damaging it, use the same harmonic balancer puller tool as shown below Ê to remove the hub that is used to remove the flywheel, except use two long 1/4" coarse thread grade 8 bolts with flat washers.

After the hub is removed, sometimes the 1/4" steel dowel pin will remain in the flywheel. This pin only purpose is to prevent the hub from slipping on the flywheel when engine power (torque) is applied. Anyway, when the pin gets stuck, either use locking Vise-Grips to remove the pin, or drive the pin out from the backside of the flywheel with a steel punch and hammer. When the pin is removed, it'll be a good idea to drill-out or enlarge the hole in the flywheel to 17/64" to prevent the pin from being stuck (again) if the hub needs to be removed again. If the pin fits loose in the hub, use high strength liquid threadlocker to secure the pin in the hub. And do not drill-out or enlarge the 5/8" hole in the hub! It must fit on the 5/8" crankshaft stud snug to prevent the hub from wobbling and running out of balance on the crankshaft.

To remove the flywheel from a Kohler (or virtually any) small engine, remember, the retaining nut or bolt have right-hand threads. And there's either 5/16-18 UNC (coarse thread) (small flywheels) or 3/8-16 UNC (coarse thread) (large flywheels) bolt holes for use with grade 8 bolts with a flat washer and a quality-made gear puller to remove the flywheel from the crankshaft. A hand tap may need to be used to clean the dirt and debris from the threads in the bolt holes. Remove the flywheel with a quality-made automotive harmonic balancer/vibration damper puller tool (Lisle Corporation makes a quality puller) that have fine threads and with a quality-made 1/2" impact wrench (with a large capacity [minimum 30 gallon] air compressor reservoir tank) to literally "pop" the flywheel off the crankshaft taper. Be sure the puller bolt is centered on the crankshaft, too. Avoid using an low-quality imported puller because it might move sideways when under pressure and break off the stud or bend the bolt. Use the protective cap that's supplied with the puller to prevent from damaging the threads on the end of the crankshaft. Apply grease or motor oil on the threads of the center threaded shaft to increase the pulling torque. The puller tool require either two 5/16" or two 3/8" diameter grade 8 coarse thread bolts with a thick flat washer under each bolt head so the head won't pull through the puller's slots. And use bolts that's long enough so the threads can penetrate the entire length of the threaded holes in the flywheel to prevent the threads from being pulled out. Use a tap to clean the threads in the flywheel if necessary. And although some flywheels are stubborn to remove, just remember, it'll eventually come off. It's not made on the crankshaft!

Personally, I use a quality-made 1/2" impact wrench running off of 150 psi of pressure with a 60 gallon air compressor tank and a Lisle harmonic balancer puller with grade 8 bolts w/flat washers threaded deep into the flywheel threads to remove Kohler flywheels. I ain't never had one that was so stubborn it took a lot of effort to remove. My set up pops them off every time with very little effort! You can hear the air impact wrench when it gets under a severe strain, it starts to slow down and then POW, the flywheel pops loose.

On most aluminum block engines, such as Briggs & Stratton, Tecumseh, etc., a flywheel knock-off tool can be used to remove the flywheel. You can get a knock-off tool at virtually any place that sells small engine parts, and they come in 4 different sizes: 1/2" hole for older B&S engines, 7/16-20 UNF, 1/2-20 UNF (fine thread) and 5/8-18 UNF.

To use the knock-off tool, for an older B&S engine with the crankshaft that has a long unthreaded shaft that protrudes into the starter clutch, the tool is placed on the end of the shaft, and for all other engines with a threaded stud on the end of the crankshaft, the tool is threaded onto the stud. A crowbar or pry bar is wedged under the flywheel against the engine block to provide extra leverage (and to prevent breaking the rod journal on the crankshaft if it's cast iron or bending the crankshaft if it's steel), then a 2-3 lb. hammer is used to sharply strike the tool perpendicular to literally "pop" the flywheel free from the crankshaft taper. To prevent from damaging the threads in the tool and on the crankshaft stud, always thread the tool all the way on the stud, and then back it off 1/2 turn. And don't strike the knock-off tool at an angle, or the stud on the crankshaft could get bent or break off!

But on flywheels with no threaded holes to use the automotive harmonic balancer/vibration damper puller tool, a knock-off tool of the correct thread size with a pry bar wedged under the flywheel and a 2-3 lb. hammer can be used to remove the flywheel. Be sure to strike the tool perpendicular, too!

IMPORTANT! The Incorrect and Dangerous Way To Remove A Small Engine Flywheel -

Most Kohler crankshafts are made of somewhat brittle cast iron material. So NEVER hit or strike the end of the crankshaft with a big hammer to remove a flywheel! And DO NOT attempt to use a wrecking bar (crowbar) to "pry" the flywheel off the crankshaft! Also, never use a large [2 or 3 jaw] outside gear puller to remove a flywheel. Doing any of these could break or crack the crankshaft and/or possibly crack the flywheel or break it in half. AND DEFINITELY DO NOT USE A KNOCK-OFF TOOL WITH A BIG HAMMER ON A KOHLER CRANKSHAFT WITH THE 5/8" STUD TO REMOVE THE FLYWHEEL! Being the crank is made entirely of cast iron, the stub will likely to break off!

A true story: One of my customers brought his walk-behind rotary lawn mower with a 3.5hp Tecumseh engine (model LAV35) to me just to have the flywheel removed. When I had the mower on my work table to remove the flywheel, I noticed the flywheel was wobbly but still tight on the crankshaft. Then I found that the crankshaft was broken in two at the connecting rod journal. I thought, "This is odd." So I called my customer to tell him about this, and he said his neighbor tried to "pop" the flywheel off with a 10 lb. sledge hammer. (This obviously happened with the mower on the ground and the threaded end of the crankshaft was hit by the hammer at full swing.) Reminds me of the old joke: "Hold my beer and watch this!"


About Crankshafts Breaking at High RPM -

A stock crankshaft should be fine as long as the engine isn't over-revved for a long period of time, which could cause it to go into harmonic vibrations, which would cause it to break in two. But if dynamically precision spin-balanced, a cast or billet steel crankshaft should survive as high as 7,000 RPM for a long time if they've been precision-balanced to the connecting rod and piston assembly using a dynamic balancing machine. Some cast cranks break, and steel crankshafts are prone to breaking, too. When they do break, it's usually due to: being in an engine that broke the connecting rod and the rotating assembly came to a "sudden stop", and the flywheel kept wanting to spin, but cracked the crank instead; an out of balance flywheel (even CNC-machined steel flywheels should be dynamically precision spin-balanced, too); and/or an out of balance starter pulley on the PTO end (which should also be precision-balanced). An out of balanced flywheel or pulley will cause the crankshaft to flex a few thousands of an inch at high RPM. When they flex, this causes metal fatigue, which creates a microscopic crack next to the rod journal, and they eventually break. Kind of like bending a piece of wire back and forth by hand, until it eventually breaks. I heard that the Magnum crankshafts are tougher than the old K-series cranks when precision-balanced. And when a crankshaft breaks at high RPM, it can also break a cast cam or bend a billet steel cam, which could crack the engine block at the cam pin on the flywheel side.


Always Use a Steel Flywheel on a Pulling Tractor Engine That Turns Above 4,000 RPMs!

The smaller (8") steel flywheels require that a billet pulley be installed on the PTO end of the crankshaft and a starter cart w/V-belt be used to crank the engine to start it. (Which can be a major inconvenience if you have no assistance.) And the bigger (9") steel flywheels will accept a ring gear and can be used with a gear starter fastened on the side of the engine block. (Which I think is much more convenient.) Also, the heavier (31 lb.) 9" flywheel is more suitable for stock engines that turn around 4,000 RPMs, and the lighter (19 lb.) 9" steel flywheel is ideal for engines that run at wide open throttle.

Most of the time a heavier-than-stock, custom-made, machined steel flywheel will add more "grunt" or more torque to an engine when pulling. In our experience, a light-weight flywheel will cause an engine to lose power toward the end of a pull. Light-weight flywheels are actually made for high speed racing applications, such as for drag racing or race cars. A lightweight flywheel works great for circle track racing because they allow the engine to accelerate quicker and regain the RPM after coming out of the turns. A heavy flywheel will "bog" an engine down and make it sluggish upon acceleration.

Pulling tractors on the other hand need ground speed (momentum) to do well in a pull, with the use of a heavier-than-stock flywheel. Once a heavy flywheel is spinning, it's hard to stop it or slow it down. A heavy flywheel may somewhat cause a [stock] engine to rev up slower, but once it's revved up, and because of the greater momentum force or increase of weight in the rotating mass, it'll "hold" the RPM longer, allowing a tractor to pull the sled right out the gate.

Remember, there's only two things to be gained by using a heavy steel flywheel; 1: the safety of steel versus cast iron, and 2: the increase in rotating mass with use of a heavier-than-stock flywheel. This means that a heavy flywheel will help an engine to produce more torque at higher RPM, which is very important for a pulling engine. A heavy flywheel (heavier-than-stock) will, without a doubt, will add more lugging power to an engine. That's why they're used on the large farm tractors. By the way - the average 9-1/2" diameter OEM (Original Equipment Manufacturer) cast iron flywheel for the single cylinder K241-K361 Kohler K-series engines with the starter ring gear and full integrated fins (fan blades) weighs 23-24 lbs.

By the way - covering a shiny (new) billet steel flywheel with clear gloss enamel acrylic coating will help identify it visually as made of steel. Otherwise, if it's covered with colored paint, it'll be somewhat difficult to tell right away rather if it's a factory cast iron or steel flywheel. The enamel coating will also help protect the steel flywheel from rusting over time. (I think a nicely painted pulling engine looks good with a shiny [clear coated] steel flywheel.) Actually, the best way to determine if an engine has either a cast iron or steel flywheel (if they look the same) is to tap it with a small hammer or wrench. Cast iron will make a "clunk" sound, and steel will have a high pitch ring to it.

Here's the dimensions if you want to fabricate a 9-1/2" diameter steel flywheel for the K241-K361 single cylinder Kohler engine:

If the above dimensions are somewhat confusing, then perhaps it's best to acquire a Kohler flywheel and take the measurements off of it.

By the way - the flywheels for Kohler K-series and Magnum engine models K241/M10, K301/M12, K321/M14, K341/M16 and K361 will interchange because they all have the same size taper on the crankshaft and in the flywheel, and most of them have two or four threaded holes for driving accessories, and for using an automotive harmonic balancer/vibration damper puller tool to remove the flywheel from the crankshaft. Also, the same flywheel ring gear (gear starter) for Kohler engine models K241/M10, K301/M12, K321/M14, K341/M16, K361, KT17, KT17 series 2, KT19, KT19 series 2, MV16, M18, MV18, M20 and MV20 will interchange. They are all identical.

And adding a heavy pulley on the PTO end of the crankshaft would help add torque to the engine at high RPM. But if/when the engine bogs down upon launch at the starting line or several feet from the starting line, it may be hard to get it to rev back up due to the extra spinning weight. So you gain one thing, but may lose another.


IMPORTANT! NEVER INSTALL A DIRTY FLYWHEEL ON A DIRTY CRANKSHAFT!

Before installing the flywheel on a crankshaft, always thoroughly clean both tapers with a clean cloth (white in color, to see the dirt) or clean shop towel to remove any dirt, oil or debris from the crankshaft taper and most importantly, inside the flywheel taper. It's okay to use electrical contact cleaner, brake parts cleaner, cleaning solvent or paint thinner to clean the tapers because these products leave no oily residue when they dry. And use emery cloth to remove any light rust on the surface of the tapers. Clean both tapers thoroughly. This is very important because there must be direct metal-to-metal contact between the two tapers for a secure bonding of the parts. Because the flywheel must keep up with the rapid acceleration (torque or driving force) of the piston via the crankshaft. Do not use anti-seize compound for easy removal of the flywheel later! This includes any type of flywheel, steel, cast iron or aluminum. For assurance, high strength liquid threadlocker (Red Loctite, Permatex or equivalent) can be applied inside the flywheel taper or on the crankshaft taper to prevent the flywheel from slipping on the crankshaft. Thorough cleaning of the tapers should still be performed even with the use of the threadlocker. Be sure to allow the threadlocker to fully cure (dry/harden) overnight at room temperature before starting the engine because if the threadlocker is still in liquid form, the rapid torque of the acceleration of the engine could cause the flywheel to slip slightly and possibly loosen on the crankshaft.

If the threadlocker is used, an acetylene torch will be required to soften the threadlocker in order to remove the flywheel. If the flywheel needs to be removed later, use a quality gear puller and an air impact wrench or some muscle. Any oil, dirt or debris trapped in the tapers, or even anti-seize, will, without a doubt, allow the flywheel to slip or rock back and forth on the crankshaft, in which will shear the key, wallow out both keyways and possibly crack or break the flywheel and/or crankshaft. Dirt/oil on the tapers is the main reason why most custom-made billet steel high-performance crankshafts break. And if the flywheel use a Cub Cadet or billet aluminum clutch hub adapter, be sure to install the [1-3/8" o.d.] thick flat washer under the retaining nut or bolt and then torque the nut or bolt to the proper specs.

NOTE: As long as the rotating clutch components are trued-up in a metal lathe to minimize vibration, and the wide, thick washer is used inside the hub to secure the hub to the flywheel, and the flywheel retaining nut or bolt properly torqued, the OEM (Original Equipment Manufacturer) cast aluminum clutch hub have been proven to hold up to a wide open throttle pulling engine. IMPORTANT: If you don't feel comfortable using a metal lathe, please consult a professional and experienced machinist with a lathe.


The Best Way to Torque the Flywheel Retaining Bolt or Nut - Top of Page

Personally, I use an air impact wrench to lightly snug the flywheel nut or bolt against the flywheel, then I finish torquing it with a torque wrench. The flywheel won't rotate with an air impact wrench. If an air impact wrench isn't available, and if the flywheel has a starter ring gear, clamp Vise Grips on the edge of the ring gear, allow it to bump against the bolt boss on the bearing plate and then the flywheel nut or bolt can be loosened to be removed, or when installing, torqued to specs. But if the flywheel doesn't have a ring gear, clamp the Vise Grips on the PTO end of the crankshaft, install a long bolt in one of the bolt holes on the PTO end of the block, and allow the Vise Grips to bump against the bolt to loosen or torque the flywheel nut or bolt. As easy and simple as this may be, do not place a steel bar through the fins of the flywheel to loosen or torque the bolt or nut! Being the fins are made of brittle cast iron, doing this could cause a fin to break off. If a fin breaks off, this will cause the flywheel to be dangerously out of balance, and the engine will vibrate badly.

With the tapers clean, and when the flywheel nut or bolt is tightened or torqued to specs, the "squeezing" action of the flywheel taper actually "grips" it to the crankshaft, guaranteeing positive metal to metal contact, with no slip whatsoever. Torque the 15/16" nut at 65 ft. lb., and the 3/8" bolt at 40 ft. lb., but do not overtorque it! (As with an air impact wrench.) And Kohler's flywheel [castle] nut is self tightening. Therefore, a lock washer isn't necessary. But sometimes the nut will wear and tend to loosen over time. When this happens, the flywheel could loosen, and the keyway in both the flywheel and crankshaft will become damaged beyond repair. Therefore, a new all metal self locking nut is required for a professional repair. But use a split lock washer on the bolt. And use a grade 8 bolt, nothing less.


IMPORTANT! A cast iron flywheel with a crack in it, even a small crack, should never be used on any engine!

Oil, grease, dirt on the crankshaft and/or flywheel tapers or even an overtorqued nut or bolt could cause the center in a cast iron flywheel to crack in the keyway or the threaded stud of the crankshaft to break off. Cast iron flywheels always crack at the weakest point, which is at the keyway. If the crack is welded, and when the flywheel is installed on the crankshaft, and the nut or bolt is torqued to specs, the taper would still split next to the weld. But steel flywheels don't crack (or break).

A crack in a flywheel will cause an engine to vibrate severely, plus it'll be noisy. (It'll make a "clunk, clunk" sound at idle.) The crack will get worse over time, causing the flywheel to split in half at high RPM. If this happens, the two halves could cause severe bodily injury or possibly death if they were to become airborne and strike an innocent bystander.

The only valuable part on a cast iron flywheel with a crack in the keyway would be the starter ring gear. It can be installed on a [good] cast flywheel or a steel flywheel. Cast iron flywheels that's in good condition works great up to 4,000 RPM. (The factory setting of maximum RPM for virtually all small gas engines, including all of Kohler engines is 3,600.) Above 4,000 RPM, a steel flywheel is highly recommended for safety.

To minimize damage to the keyways, do not use a steel flywheel key. A heat-treated hardened key would be even a worse thing to use. An soft aluminum (4041 hardness) key works best. To keep a keyway in a cast flywheel from splitting, it's best to use soft aluminum key. The reason for this is if the connecting rod breaks resulting in instant crankshaft lockup, the soft key will prevent damage to the flywheel and crankshaft. The aluminum key will shear in two, allowing the flywheel to slip on the crankshaft, preventing damage to either the flywheel or crankshaft. A steel key will cause a cast iron flywheel to crack or break, or if a flywheel loosens on the crankshaft, it'll wallow out the keyways. But if an aluminum V-belt starter pulley with ignition timing degree marks is installed on the PTO end of the crankshaft, there's really no need to install a flywheel key. The only reason most small engines use a flywheel key is to time the ignition, and not to prevent the flywheel from slipping on the crankshaft.


Removing the Majority of the Integrated Fins from the Flywheel to Reduce Drag on Engine and Boost Horsepower -

One sure way to increase the power output about 30% of a 4,000 RPM stock pulling engine is to reduce the amount of [air] drag that the flywheel fins cause. To do this, the majority (about 3/4) of the fins will need to be removed from the flywheel. For competition pulling, the flywheel will still provide plenty of fresh air to sufficiently cool the engine. When the engine can stay cool from the short fins on the flywheel while pulling, this will help the engine produce more power. Because excessive heat can rob an engine of horsepower. Steel flywheels don't offer this advantage. Shortening the fins on a flywheel shouldn't be done on an engine that's used for general lawn and garden use, heavy towing or pushing snow because the engine could run hotter than normal after running for a long period of time, which could cause premature engine wear.

How to Remove the Integrated Fins -

A heavy duty 14" electric chop saw with a metal cut-off wheel, like the one that most automotive muffler shops use, can be used to remove the majority of the fins from the flywheel. An alternative is with a large metal cutting CNC machine, this would work better. The fins would be the same height and the cutting process would be much safer. But to manually cut the flywheel fins off using a heavy duty electric chop saw with a metal cut-off wheel...

  1. First of all, wear eye protection or safety glasses and a dust and particle mask or surgical face mask to keep from breathing in the cast iron and cutting wheel dust particles. (If you don't wear a mask, you may wish you did.)
  2. Position the flywheel in alignment with the cutting wheel, firmly hold the flywheel with one hand and carefully bring the cutting wheel down even with the outside taper in the flywheel. Cut a few fins, then rotate the flywheel, and keep doing this until all the fins are removed. Try to keep all the fins even and in alignment, too.
  3. Now chuck the flywheel in a large metal lathe to true up the fins so they'll all be the same height. (This require less effort to rebalance.) IMPORTANT: If you don't feel comfortable using a metal lathe, please consult a professional and experienced machinist with a lathe.
  4. To spin-balance the flywheel, a 1-1/2" diameter x approximately 24 mild steel rod machined with a precision-machined taper to match the angle of the taper in the flywheel, and a threaded bolt hole in the end to retain the flywheel will need to be fabricated for chucking the flywheel in the metal lathe. This shaft is also used to spin-balance the flywheel afterwards. IMPORTANT: If you don't feel comfortable using a metal lathe, please consult a professional and experienced machinist with a lathe.

IMPORTANT! Due to the brittle material, a cast iron flywheel (altered or unaltered) shouldn't be used on an engine that runs at high RPM or at wide open throttle. Due to the combination of severe centrifugal force and engine vibration, the flywheel could explode, causing serious injury or possible death to a bystander. The Kohler Magnum plastic flywheel fan shouldn't be ran above 4,000 RPM either, because it can explode, too.

A stock Kohler flywheel with about 3/4 of the fines removed will allow the engine to have approximately 30% increase in horsepower. And DEFINITELY without a doubt (and using common sense), any flywheel with the majority of the fins removed should definitely be dynamically precision spin-balanced with an automotive crankshaft/flywheel balancing machine. The same machine for balancing the crankshaft to the connecting rod/piston assembly can be used to balance flywheels, too. The flywheel should be balanced to within 1/10th of an ounce (0.1 lb.) or 1 gram. For an example of how much 1/10th of an ounce is, a dime (10¢) weighs exactly 1/10th of an ounce (or 2 grams).

NEVER use an automotive tire bubble balancer to balance a flywheel! Also, make sure the flywheel has all the internal magnets intact (for the charging system) or remove the magnets altogether if using no charging system. And do not spin a cast flywheel (on the engine) no faster than 4,000 RPM! Or better yet, install a billet steel flywheel and an electric fan to cool the engine.


IMPORTANT! IMPORTANT! IMPORTANT! IMPORTANT!
Below Ê are the results of a OEM Kohler cast iron flywheel that is out-of-balance, with a crack in the keyway, a broken-off fin, and/or when spun at wide open throttle

The photos below Ê are the results of a 9-1/2" diameter cast iron Kohler flywheel when it was spun at wide open throttle in a garden pulling tractor. This was a very serious accident that could have been a life-threatening tragedy. Remember: a well-constructed and precision-balanced steel flywheel is cheap compared to hospital bills, rehabilitation or funeral costs and not to mention the seemingly never-ending lawsuits!

The guy (name withheld) had just recently bought the Pro Stock motor. He already had the clutch setup on the flathead Kohler twin he was running. According to what a friend of his told me (that also has a Pro tractor) the guy called him and asked would it be ok just to start the motor so he could hear it run. He was told not to turn it over 3,000 RPM. There is no question the guy knew he needed a steel flywheel and safety shields on the tractor before pulling it. I am confident those measures would have been on it before he pulled it the first time. There "was" someone standing by the tractor - the guy that owns it. He was working the throttle standing right in-line with the cast iron flywheel. You can see what it did to the air filter. Apparently it hit the carburetor and filter on its way to hitting him. It wasn't his leg that got the brunt of the piece of flywheel!

He just got too eager to find out what he had purchased and made a bad decision. It's an injury that will be with him the rest of his life. The point of putting these pictures on this site is so other pullers would not make the same mistake. I'm confident he is embarrassed by his actions...but he didn't have to share those pictures, ya know. I admire him for sharing these photos, and he's still suffering from the accident. - Story by Ron Ethridge

Also, check out this video: Farmall 1206 Breaks in Half when flywheel Explodes - YouTube (https://www.youtube.com/watch?v=y7gKbk0jyyM).

IMPORTANT! It's highly recommended that all flywheels, despite the material it's made of, be dynamically precision spin-balanced with an automotive crankshaft/flywheel balancing machine. The same machine to balance a crankshaft can be used to balance a flywheel, too. And never use an automotive tire balancer or "bubble balancer" to balance a flywheel! They are NOT precision enough for a flywheel!

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If you would like to purchase any of the parts or services listed in this website, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO (Missouri) 65203-9136 USA | Phone: 1-573-256-0313 (shop) | 1-573-881-7229 (cell). Please call Monday-Friday, except holidays, 9am to 5pm, Central time zone. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) A-1 Miller's shop is open to the public from 9am to 5pm, including weekends, except holidays. Please call before coming so I'll be here waiting for your arrival. E-mail: pullingtractor@aol.com. Directions to our shop | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. If you're the kind of person who don't trust delivery/shipping companies (mis)handling your high-dollar and fragile merchandise, you can make the long drive to A-1 Miller's shop to personally drop off and/or pick up your carburetor, clutch assembly, engine, transaxle, tractor, etc. "The road to a friend's house (or shop) is never long." (We're planning to relocate to other property with a bigger and better shop so we can provide many more parts and services.) Please click here to place an order.
High Quality Inductive Handheld Small Engine Wireless Tachometer. A tachometer is required in setting the correct RPMs (normally 3,200 or 3,600 maximum for small engines) of an engine to prevent from over-revving and possible damage to the engine or dangerous flywheel explosion. For gas/spark ignite engines only. Works with magneto and battery-powered ignition systems. Very accurate. This handheld analog tach works great for checking/setting the RPM on various small engines in the shop, and/or for checking/setting the RPM [tech] on stock governored competition pulling engines. Hold sensor (antenna) close to spark plug wire for reading. Operates off a self-contained replaceable 9 volt battery. Has built-in battery voltage check. Reads up to 5,000 RPM on the low scale, and 15,000 RPM on the high scale.
  • $85.00 each, plus shipping & handling.
High Quality Inductive Small Engine Tachometer/Hour Meter. A tachometer is required in setting the correct RPMs (normally 3,200 or 3,600 maximum for small engines) of an engine to prevent from over-revving and possible damage to the engine or dangerous flywheel explosion. Very accurate. Can be used for lawn & garden equipment or competition pulling engines. Can be hand-held to temporarily set engine RPM or permanently mounted to monitor engine RPM at all times. Large 3/8 inch LCD display. Works with magneto and battery-powered ignition systems. Works with all spark ignition engines by selecting engine type using S1 and S2 buttons. If tachometer does not turn on automatically as soon as engine starts, press and hold the two buttons at the same time. Instructions included. Tachometer reads up to 99,999 RPM. Hour meter reads up to 9999:59 hours/minutes then resets to Zero. Programmable maintenance hour setting with service icon, a reminder when to change oil or other service. Can be manually reset to Zero hours. Programmable maintenance hour setting with service icon, a reminder when to change oil or other service. Easy installation: Single wire wraps around spark plug wire and secured with two supplied nylon zip-ties. No wire terminal connections required. Tachometer can be surface-mounted and secured with two screws. Has battery that last up to 4 years. Sealed unit; weather and water resistant. Dimensions: 2" wide x 1-3/4" depth x 3/4" height.
  • $20.00 each, plus shipping & handling.
High Quality Digital Tachometer/Proximity Sensor Kits. A tachometer is required in setting the correct RPMs (normally 3,200 or 3,600 maximum for small engines) of an engine to prevent from over-revving and possible damage to the engine or dangerous flywheel explosion. Will work with single- or twin-cylinder small engines or multi-cylinder automotive engines, gas or diesel. Works with magneto (with a battery to power the proximity sensor and tachometer) and battery-powered ignition systems. Very accurate. Can be used for lawn & garden equipment or competition pulling engines. Designed to be permanently mounted to monitor engine RPM at all times. This precision digital tachometer operates with external power and on the same principle as my crank- or flywheel-trigger ignition systems with a proximity sensor to detect a target, which can be a small ferrous steel screw or pin, or magnet in a rotating disc on the crankshaft or on/in flywheel. Cannot be wired in conjunction with the Dynatek Dyna S or PerTronix Ignitor ignition modules. It must be wired separately or can be used with any of my crank trigger ignition systems that also use a proximity sensor. A sturdy steel or aluminum bracket will need to be fabricated by customer to mount the sensor in close proximity of the detector/trigger target. Set air gap/clearance at .010"-.188". Tachometer works with 8-24 volts DC, proximity sensors works with 6-36 volts DC. Tachometer can be in-dash or panel-mounted. Dimensions for mounting hole: 3" wide x 1-17/32" wide. Tachometer measures 1" in depth. Tachometer works with 8-24 volts DC, proximity sensors works with 6-36 volts DC. Dimensions of each proximity sensor below: 15/32" (12mm) diameter x 1-3/8" thread length. Some proximity sensors have an LED (Light Emitting Diode) on the rear of unit. If the proximity sensor is wired incorrectly, the LED will stay on and go off when activated. Displays up to 9,999 RPM. Very accurate. Tachometer returns to zero [0000] when power (ignition) is turned off. Wiring Instructions: #1 wire on tachometer connects to brown wire on (either) proximity sensor and ignition switch (12 volt power), #2 wire on tachometer connects to blue wire on (either) proximity sensor and engine/chassis ground (battery negative (–) post), and #5 wire on tachometer connects to black wire on (either) proximity sensor. Wires #3 and #4 connects to nothing. Wiring can also be integrated with crank trigger ignition with a proximity sensor. Choice of RED or BLUE numeric display.
  • Tachometer only. Can be used with virtually any Normally Open 3-wire hall effect, inductive or cube-shaped proximity sensor. $12.00 each, plus shipping & handling.
  • Complete Kit with Tachometer and 15/32" Diameter x 2-1/2" Length x 43" Cable Length Hall Effect Proximity Sensor. (Senses the South pole of a small magnet embedded in an aluminum rotating locking collar, disc, or OEM magnet embedded in a flywheel.) $22.00 each, plus shipping & handling.
    • Aluminum Locking Collar w/Embedded Rare Earth Magnet and Allen Set Screw. Please specify diameter of crankshaft PTO end for locking collar w/embedded rare earth magnet. Most common crankshaft PTO end diameters are 1" and 1-1/8", but 3/4", 1-1/4", 1-3/8", 1-7/16" and 1-1/2" are rare. Most billet steel crankshafts have a 1-1/2" diameter PTO end (raised shoulder). Other sizes available. $15.00 each, plus shipping & handling.
  • Complete Kit with Tachometer and 15/32" Diameter x 2-1/2" Length x 43" Cable Length Inductive Proximity Sensor. (Senses the head of a small steel screw in a rotating locking collar, disc or flywheel.) $25.00 each, plus shipping & handling. . [Return to previous section]


Shielding of the Flywheel is Important!

I remember years ago, I was reading a club's rules, and it stated that all tractors must have a steel flywheel, and it must be shielded 360º with minimum 1/4" thick steel. I asked one of the pullers of the club, "why shield a steel flywheel? It's not going to break." And he told me: "There's a possibility that the end of the crankshaft could break off."

Actually, it's not rare that this kind of thing happens. It's happened to various pullers. The end of a crankshaft, despite if it's steel or cast iron, can break off next to the flywheel. It's a slight possibility. But then again, it could happen. Like the old saying goes: "A bad apple will spoil the bunch." And remember Murphy's Law? Must be prepared for the unexpected. So need to shield them flywheels folks, before a catastrophe happens.


Advertisement: (Updated 7/9/18)
If you would like to purchase any of the parts or services listed in this website, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO (Missouri) 65203-9136 USA | Phone: 1-573-256-0313 (shop) | 1-573-881-7229 (cell). Please call Monday-Friday, except holidays, 9am to 5pm, Central time zone. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) A-1 Miller's shop is open to the public from 9am to 5pm, including weekends, except holidays. Please call before coming so I'll be here waiting for your arrival. E-mail: pullingtractor@aol.com. Directions to our shop | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. If you're the kind of person who don't trust delivery/shipping companies (mis)handling your high-dollar and fragile merchandise, you can make the long drive to A-1 Miller's shop to personally drop off and/or pick up your carburetor, clutch assembly, engine, transaxle, tractor, etc. "The road to a friend's house (or shop) is never long." (We're planning to relocate to other property with a bigger and better shop so we can provide many more parts and services.) Please click here to place an order.
9-1/2" Lightweight Steel Flywheel. Has machined step for installation of Kohler starter ring gear. Weighs 19 lbs. w/ring gear. Approximately same weight as OEM Kohler flywheel w/ring gear. Ideal for wide open throttle competition pulling engines (Hot Stock, Stock Altered, Pro Stock, Super Stock, Modified) for more top-end power and torque. Precision CNC-machined in the USA with lazer-etched timing marks. Does not include ring gear - reuse ring gear from an OEM Kohler flywheel.
  • $205.00 each, plus shipping & handling.
9-1/2" Heavyweight Steel Flywheel. Has machined step for installation of Kohler starter ring gear. Weighs 32 lbs. w/ring gear. Approximately 13 lb. heavier than stock OEM Kohler flywheel. Provides additional horsepower and torque. Ideal for 4,000± RPM stock competition pulling engines for more low-end lugging power and torque. Precision CNC-machined in the USA with lazer-etched timing marks. Does not include ring gear - reuse ring gear from an OEM Kohler flywheel.
  • $205.00 each, plus shipping & handling.
Kohler K181 Flywheel for the 5-1/2" 15/20 Amp Charging Stator. Replace damaged flywheel, or use this type of flywheel with the 5-1/2" stator to convert a K181 engine with a stator containing a failed magneto ignition coil integrated with a weak output 10 amp charging coils under the flywheel to the battery-powered ignition system. OEM Kohler part # 41 025 17-S.
  • Used and in excellent condition. $250.00 each, plus shipping & handling. (When available.)
  • New. $505.08 each, plus shipping & handling.
8" diameter OEM Kohler flywheel for engine models K241-K361. Used and in excellent condition. With full fins. Use with starter/generator for general lawn and garden use. This flywheel is for battery ignition only, not magneto or solid state ignition, but can be used with my PerTronix Ignitor crank trigger ignition system. In excellent condition and unaltered. No crack in the keyway, no broken or missing fins. This flywheel is for stock engines only; not to be turned above 4,000 RPM! Discontinued from Kohler. OEM Kohler part # 47 755 02-S.
  • $50.00 each, plus shipping & handling. (When available.)


9-1/2" diameter OEM Kohler flywheel for engine models K241-K361. Used and in excellent condition. With full fins, with internal charging magnets for 5-1/2" o.d. stator. For general lawn and garden use. Has narrow edge. This flywheel is for points/condenser ignition only, not Breakerless, magneto, solid state ignition or crank trigger ignition. In excellent condition and unaltered. No crack in the keyway, no broken or missing fins. This flywheel is for stock engines only; not to be turned above 4,000 RPM! Discontinued from Kohler. OEM Kohler part #'s 47 025 22-S or 47 025 24-S.

  • Flywheel without ring gear. Customer installs own ring gear. $50.00 each, plus shipping & handling. (When available.)
  • Flywheel with ring gear for the 10 tooth starter gear. $70.00 each, plus shipping & handling. (When available.)


9-1/2" diameter OEM Kohler flywheel for engine models K241-K361. Used and in excellent condition. With internal charging magnets for 5-1/2" o.d. stator. For general lawn and garden use. Has 3/4" wide edge. This flywheel is for battery ignition, not Breakerless, magneto or solid state ignition, but can be used with my crank trigger ignition system. In excellent condition and unaltered. No crack in the keyway, no broken or missing fins. This flywheel is for stock engines only; not to be turned above 4,000 RPM! Discontinued from Kohler. OEM Kohler part #'s 47 025 22-S or 47 025 24-S.

  • Flywheel without ring gear. Customer installs own ring gear. $75.00 each, plus shipping & handling. (When available.)
  • Flywheel with ring gear for the 10 tooth starter gear. $100.00 each, plus shipping & handling. (When available.)


9-1/2" diameter OEM Kohler flywheel for engine models K241-K361. Used and in excellent condition. With full fins and internal charging magnets for 5-1/2" o.d. stator. Has projection (hump) for BreakerLess Ignition or crank trigger ignition. For general lawn and garden use. This flywheel is for battery- or Breakerless-ignition, not magneto or solid state ignition, but can be used with my crank trigger ignition system. In excellent condition and unaltered. No crack in the keyway, no broken or missing fins. This flywheel is for stock engines only; not to be turned above 4,000 RPM! Discontinued from Kohler. OEM Kohler part # 47 025 28-S.

  • Flywheel without ring gear. Customer installs own ring gear. $100.00 each, plus shipping & handling. (When available.)
  • Flywheel with ring gear for the 10 tooth starter gear. $125.00 each, plus shipping & handling. (When available.)


9-1/2" diameter OEM Kohler flywheel for engine models K241-K361. Majority of fins removed, dynamically precision spin-balanced with an automotive crankshaft/flywheel balancing machine. Without internal charging magnets. A stock Kohler flywheel with about 3/4 of the fines removed will allow the engine to have approximately 30% increase in horsepower. This flywheel is recommended for stock competition pulling engines only; not to be turned above 4,000 RPM! Click picture to the right for a larger view.

  • Flywheel without ring gear. Customer installs own ring gear. $135.00 each, plus shipping & handling. (When available.)
  • Flywheel with ring gear for the 10 tooth starter gear. $160.00 each, plus shipping & handling. (When available.)


Used ring gear for the 10 tooth starter gear for 9-1/2" diameter OEM Kohler or steel flywheel. $25.00 each, plus shipping & handling. (When available.)


Your OEM Kohler flywheel - Remove majority of fins and precision spin-balance. Includes remove most of the integrated fins, chuck it in our metal lathe to true up the fins so they're all even and then precision spin-balance it. Recommended for stock competition pulling engines only; not to be turned above 4,000 RPM! $85.00 labor, return shipping extra.

Internal Flywheel Magnets for Alternator Charging System. Fits aluminum and cast iron block single and twin cylinder Kohler engine models K141, K161, K181, K241, K301, K321, K341, K361, KT17/KT17 series 2, KT19/KT19 series 2, KT21, M8-M16, MV16, M18, MV18, M20, MV20, K482, K532, K582, CH1000, CH11-CH26, CH430, CH450, CH620-CH682, CH730-CH752, CH940, CH980, CV1000, CV11-CV25, CV430-CV493, CV620-CV682, CV725, CV730-CV940, CV960, CV980, ECV630-ECV680, ECV730-ECV749, ECV630-ECV680, ECV730-ECV749, ECV850-ECV880, ECV940, ECV980, FCV740, KT610, KT620, KT715-KT745, LH430, LH640-LH690, LH750, LH755, LV625-LV680, PCH680, PCH740, PCV680, PCV740, PCV850, PCV860, SV470-SV480, SV530-SV590, SV600-SV620, SV710-SV740, SV810-SV840, TH16, TH18, TH575, ZT710-ZT740, except certain early John Deere with a single cylinder Kohler engine with the 4-1/4"± charging stator, and larger Tecumseh engines with an alternator charging system having the 5-1/2" diameter stator. Magnet(s) may come in 3/4" or 7/8" height, but will work the same. Comes with North-South poles identified. Not available separate from Kohler. Used and in excellent condition.
  • $10.00 each, plus shipping & handling. (When available.)
  • $50.00 per set of 6 magnets, plus shipping & handling. (When available.)
Reconditioned OEM Kohler Crankshafts - [When available.]

Available for Kohler engine models K241/M10, K301/M12, K321/M14, K341/M16 and K361. These cast iron cranks are genuine Kohler, used and in excellent condition. They have either a 1" or 1-1/8" diameter x 3-1/2 PTO shaft w/1/4" wide keyway. They have good gear teeth and may have a worn or unworn connecting rod journal in either STD size or undersize. Which can be reground to .010", .020" or .030" undersize. Although .030" is rare, it's still very safe to use. FYI - To be honest, these are old, used crankshafts. So if you need one with an unworn STD size rod journal, you'll probably have a better chance of winning the lottery than finding a used Kohler K-series or Magnum single cylinder crankshaft with an unworn STD size journal. And if you're going to use a pulley, clutch, etc., on the PTO end, then I will need to know the exact dimensions of the PTO end on your crankshaft so I can match it to one that I may have in stock. For accuracy, measure the length from the oil seal shoulder out. If you have the engine's original model and specification numbers, go to kohlerplus.com (require Internet Explorer), to find the correct part number for the crankshaft, then find the dimensions and specifications of the crankshaft is here: CRANKSHAFT REFERENCE MANUAL. (require Adobe Acrobat Reader and use Google Chrome web browser for a faster download of web sites with large files.) Shipping weight: 12 lbs.

  • Crankshafts for Kohler engine models K241/M10. $100.00 each, plus shipping & handling. (When available.)
  • Crankshafts for Kohler engine models K301/M12. $125.00 each, plus shipping & handling. (When available.)
  • Crankshafts for Kohler engine models K321/M14, K341/M16 and K361. $150.00 each, plus shipping & handling. (When available.)
  • NOTE: Once installed and in use, there is no warranty or guarantee of any kind on any crankshaft purchase!

Dynamic Precision Spin-Balancing Service -

Balance (cast or steel) flywheel for Kohler K241-K361 cast iron block engines. $60.00 each labor, plus return shipping & handling.

Balance cast iron (Kohler) crankshaft and matching connecting rod and piston assembly. $200.00 per rotating assembly, plus return shipping & handling. NOTE: I will need to take your parts to the only reputable and trusted automotive machine shop in Jefferson City, Missouri that does professional engine balancing. Or you can contact Precision Machine, Inc. (PMI) to have your rotating assembly dynamically precision spin-balanced. They are located at 1703 Christy Drive, Jefferson City, MO 65101. Phone: 573-635-7214. Return To Previous Paragraph or Section

  • Regrind Crankshaft Journal - $50.00 per journal. On a twin cylinder crankshaft, $100.00 total, plus return shipping & handling. Note: The K241-K361 Kohler crankshafts can be ground as far as .030" and still be safe to use with a matching undersized bearing insert installed in the rod. And all crankshafts, rather if they're automotive or small engine, are checked for straightness before grinding. If they're bent or twisted, sometimes they can be straightened.
  • On the Kohler engine models K141, K160/K161 or K181/M8 and other makes and models of engines, if the crankshaft is worn beyond .010" and needs to be reground again, the journal can be reground to .020" and then the connecting rod can be resized so it'll fit the smaller undersize journal. I do this sometimes on engines when a .020" undersize rod isn't available. This hurts nothing and it lasts as long as an ordinary STD rod and crank journal. Price for doing this is $75.00, plus return shipping & handling. I will need your crankshaft and connecting rod.
  • Repair a broken off stud in crankshaft on flywheel end: $20.00. I drill and cut threads for a hardened 3/8" or 5/8" diameter bolt in the end of the crankshaft to secure the flywheel. And a steel bolt is much stronger than a cast iron stud. Because cast iron is brittle and steel is flexible.
  • Drill and cut 7/16-30 UNF (fine thread) threads in the PTO end of the crankshaft for a retaining washer and bolt. $20.00.
Flywheel Retaining Nuts for threaded stud on end of K-series and steel crankshafts. IMPORTANT: Apply thin coat of motor oil on threads of crankshaft before installing nut then torque each to 65 ft. lbs.
  • OEM-Type Slotted/Tapered Seat Self-Locking Nut. 5/8-18 UNF (fine thread) threads. A-1 Miller part. Discontinued from Kohler. Replaces Kohler part # 25 100 02-S. $1.50 each, plus shipping & handling.
  • All-Metal Self-Locking Nut. 5/8-18 UNF (fine thread) threads. $1.50 each, plus shipping & handling.
  • OEM-Type Slotted/Tapered Seat Self-Locking Nut. 3/4-16 UNF (fine thread) threads. Used on older K241 crankshafts and most billet steel crankshafts. A-1 Miller part. Discontinued from Kohler. Replaces Kohler part #'s X-89-11, X-119-16. $1.75 each, plus shipping & handling.
  • All-Metal Self-Locking Nut. 3/4-16 UNF (fine thread) threads. Used on older K241 crankshafts and most billet steel crankshafts. $1.75 each, plus shipping & handling.
Flywheel Retaining Bolt and Washer Kit for threaded hole in end of newer K-series and all Magnum crankshafts. Bolt: 3/8-24 UNF (fine thread) threads, grade 8 material w/split lock washer. Washer: 3/16"± thickness x 1-1/4" diameter. Torque bolt to 40 ft. lb. IMPORTANT: For proper torque and before installing, apply thin coat of oil on threads of bolt or inside threaded hole.
  • All high quality A-1 Miller aftermarket parts. $4.00 per kit, plus shipping & handling.
  • All OEM Kohler part #'s 25 086 24-S (bolt; $2.22), 12 468 03-S (thick washer; $3.69). $5.91 per kit, plus shipping & handling.
Extra Thick Flywheel / Aluminum Hub Adapter Retaining Washers. A must to secure flywheel and prevent OEM Cub Cadet or billet aluminum hub adapter breakage. Each made of steel and measures approximately 1/4" thick x 1-1/4" o.d.
  • Washers with 13/32" center hole. To be used with a crankshaft that has a 3/8" bolt, and/or aluminum hub adapter that has a 3/8" center hole.
    • A-1 Miller part. $3.00 each, plus shipping & handling.
    • OEM Kohler part # 12 468 03-S. $3.80 each, plus shipping & handling.
  • Washer with 5/8" center hole. To be used with a crankshaft that has a 5/8" stud, and/or aluminum hub adapter that has a 5/8" center hole. A-1 Miller part. Discontinued from Kohler. Replaces Kohler part # X-25-104. $5.00 each, plus shipping & handling.
  • Washer with 3/4" center hole. To be used with a crankshaft that has a 3/4" stud, and/or aluminum hub adapter that has a 3/4" center hole. A-1 Miller part. Discontinued from Kohler. Replaces Kohler part # X-25-71. $5.00 each, plus shipping & handling.
Steel Adapter Step-Washer for installing Cub Cadet cast aluminum clutch hub with 5/8" center hole to Kohler Magnum crankshaft with a 3/8" bolt. A must to center hub and prevent hub breakage! NOTE: As long as the rotating clutch components are trued-up in a metal lathe to minimize vibration, and the wide, thick washer is used inside the hub to secure the hub to the flywheel, and the flywheel retaining nut or bolt properly torqued, the OEM cast aluminum clutch hub have been proven to hold up to a wide open throttle pulling engine.
  • $12.00 each, plus shipping & handling.
Steel Rectangular Flywheel Key for early Kohler K-series engine models K241, K301, K321 with the 8" diameter flywheel and starter/generator. Dimensions: 3/16" wide x 1/4" tall x 1-3/8" length. Discontinued from Kohler. OEM Kohler part # X-366-1-S.
  • Used and in excellent condition. $3.00 each, plus shipping & handling. (When available.)


Square Flywheel Keys for Kohler K-series engine models K141, K160, K161, K181, M8, K241, K301, K321, K341, K361, KT17, KT17 Series II, KT19, KT19 Series II, MV16, M18, MV18, M20 and MV20. Dimensions: 3/16" square x 1-3/8" length.
  • Steel Flywheel Key. High quality aftermarket. $1.00 each, plus shipping & handling.
  • Steel Flywheel Key. OEM Kohler part # X-286-17-S. $1.70 each, plus shipping & handling.
  • Aluminum Flywheel Key. Made of 6061 alloy; medium-grade hardness aluminum. Replaces Kohler part # X-286-17-S. $5.00 each, plus shipping & handling.


Steel Woodruff (Semicircular) Flywheel Key for early Kohler engine models K160, K161, K181 and later 10-16hp K-series and all Magnum single cylinder engines. 3/16" wide x 1" length.
  • High quality aftermarket. $1.00 each, plus shipping & handling.
  • OEM Kohler part # X-46-3-S. $1.85 each, plus shipping & handling.


Steel Woodruff (Semicircular) Flywheel Key for most OHV aluminum block Kohler engines. 3/16" wide x 5/8" length.
  • High quality aftermarket. $1.00 each, plus shipping & handling.
  • OEM Kohler part # X-42-15-S. $1.60 each, plus shipping & handling.
Flat washer for retaining flywheel or aluminum clutch hub to flywheelFlywheel / Aluminum Hub Retaining Washers. A thick, wide washer is a must to secure flywheel and prevent clutch/driveshaft aluminum hub adapter breakage! Each made of steel and measures 1-1/4" o.d. x approximately 1/4" thick.
  • Washer w/13/32" hole. Must be used with aluminum hub that has a 3/8" hole.
    • A-1 Miller part. $3.00 each, plus shipping & handling.
    • OEM Kohler part # 12 468 03-S. $3.40 each, plus shipping & handling.
  • Washer w/5/8" hole. To be used with aluminum hub that has a 5/8" hole. A-1 Miller part. (Discontinued from Kohler.) Replaces Kohler part # X-25-104. $3.50 each, plus shipping & handling.
  • Washer w/3/4" hole. To be used with aluminum hub that has a 3/4" hole. A-1 Miller part. (Discontinued from Kohler.) Replaces Kohler part # X-25-71. $3.50 each, plus shipping & handling.
Steel Adapter Step-Washer for installing Cub Cadet cast aluminum clutch hub with 5/8" center hole to Kohler Magnum crankshaft with a 3/8" bolt. A must to center hub and prevent hub breakage! NOTE: As long as the rotating clutch components are trued-up in a metal lathe to minimize vibration, and the wide, thick washer is used inside the hub to secure the hub to the flywheel, and the flywheel retaining nut or bolt properly torqued, the OEM cast aluminum clutch hub is capable of holding up to a wide open throttle pulling engine.
  • $12.00 each, plus shipping & handling.
1/4" Steel Dowel Pin for aluminum clutch hub. 3/4. Secures above hub to flywheel to prevent slippage.
  • $1.00 each, plus shipping.
Flywheel grass/safety steel screen for use in IH-built Cub Cadet garden tractors with Kohler engine models K161 and K181. 5-9/16" diameter.
  • New Old Stock or Used and in excellent condition. Discontinued from Kohler. OEM Kohler part # 231819-S. $20.00 each, plus shipping & handling.
Flywheel grass/safety steel screen for use in IH-built Cub Cadet garden tractors with Kohler engine models K241 and K301. 7" diameter.
  • Used and in excellent condition. $120.00 each, plus shipping & handling.
  • New. OEM Cub Cadet part # KH-235190 and OEM Kohler part # 235190-S. $240.00 each, plus shipping & handling.

How to Fix/Repair a So-Called "Broken" 12 Volt Bilge Blower Fan - (Added 6/7/18)

The 12 volt bilge blower fans, like the ones pictured to the right, are not designed to be used on a garden pulling tractor. They must be reinforced to withstand normal high speed engine vibrations. Therefore, when a fan of this type is used on a garden pulling tractor and fails, what usually happens is one or both of the small screws that secures the electric motor to the plastic housing loosens and falls out, rendering the fan inoperable. Well, here's how to fix or repair the fan so chances are, it will not fail again when used on a garden pulling tractor:

  1. Use a mini pry bar / tack puller (like the one pictured to the right) and a small hammer to remove the fan blade assembly from the motor. Drive the fan blade assembly off the motor with the curved end of the mini pry bar / tack puller from inside the fan housing. To prevent from breaking the fan blade assembly, rotate it 1/3 at a time while driving it off the motor shaft. (It has a press-fit.)
  2. Remove the two small screws securing the motor to the plastic housing (if one screw haven't already dislodged and is missing).
  3. IMPORTANT - Install a #4 split lock washer on each screw [4-40 UNC screws], and tighten the screws securely.
  4. Reinstall the fan blade assembly on the motor shaft with the small hammer. (It has a press-fit.)
  5. Install the blower fan in the tractor securely with 1/4" bolts. Use flat washers under the bolt heads and split lock washers on the nuts or use locknuts. Now the fan should work better than ever and last for many years. And there's no need to use rubber mounting grommets. These will serve no purpose whatsoever. See below if you need a new reinforced high velocity 12 volt engine cooling fan.
High Velocity 12 Volt Engine Cooling Fans. Use an electric cooling fan when engine has a steel flywheel with no cooing fins. Draws 2.6 amps, produces 145 CFM. Measures 3" diameter and 5" length. Best to fasten fan on a sturdy angle steel support bracket in front of engine or behind grille in a Cub Cadet garden tractor. Motor is 100% secured and reinforced in plastic fan housing tube to withstand severe engine vibrations. Motor will not loosen or become inoperable when pulling. No need to install rubber mounting grommets. These will serve no purpose whatsoever. IMPORTANT: Do not run fan while pulling because the internal brushes could break due to normal engine vibration. Turn fan on ONLY between pull-offs or when tuning engine.


The same flywheel ring gear (gear starter) for Kohler engine models K241/M10, K301/M12, K321/M14, K341/M16, K361, KT17, KT17 Series 2, KT19, KT19 Series 2, MV16, M18, MV18, M20 and MV20 will interchange. They are all identical. To swap a starter ring gear from one flywheel to another, first of all, Kohler don't sell just the ring gear by itself. You will need to acquire a used flywheel with a good ring gear on it.

  1. To remove the ring gear from a flywheel, it's not necessary to heat it. Instead, place the flywheel with the fins facing up on a steel top work table, bench or concrete floor, then use a drift punch tool or steel rod and a 2-3 lb. hammer to remove the ring gear from the flywheel. Gently tap equally around the entire circumference of the gear to avoid distorting or bending it. It should eventually fall off.
  2. To install the ring gear on a flywheel, position the flywheel with the fins facing down on a fire-proof steel top work table, bench or concrete floor, and place the ring gear on the flywheel with the beveled edge of the gear teeth facing upward. This allows the starter gear teeth to engage more easily without causing binding, damage or wear to the teeth.
  3. Use an oxy-acetylene torch to heat the ring gear 360º to expand it so it'll install on the flywheel. (A propane torch may not get hot enough.) This should only take a few minutes. Do not use a hammer for assistance! Once the gear drops in place, it'll have a loose fit until it cools. Allow it to air-cool. Do not cool it with water. Once cooled, it'll have a tight, secure fit on the flywheel. NOTE: NEVER attempt to install (pound) a [cold] ring gear onto the flywheel with a hammer! Doing this will bend it badly out of shape and ruin it for use.
  4. Click here to watch various YouTube videos of this process: How to swap or flip a ring gear off a flywheel - YouTube (https://www.youtube.com/results?search_query=How+to+swap+or+flip+a+ring+gear+off+a+flywheel).


How to Widen the Frame Rails on a Narrow Frame Cub Cadet for Use of a Large Flywheel with a Gear Starter - (This is much easier to do on a platform work table.)

On a garden pulling tractor, it's best to use a gear starter with the larger diameter flywheel, because a starter/generator will rob the engine of valuable horsepower, which needs to be put through the rear tires. It'll be better to spin the tires than the starter/generator. As an added bonus, the bigger (heavy, steel) flywheel will add horsepower and torque to the engine at high RPMs.

The larger 9-1/2" diameter flywheel with a starter ring gear, larger K-series bearing plate and K-series flywheel housing can be installed on any K241-K361 Kohler engine for use with the gear starter, as long as there's an indention in the block just above the starter motor's mounting holes (when using the upper-mount type starter). (The small flywheel is 8" in diameter.) If the engine is being installed in a narrow frame Cub Cadet (models 70, 71, 72, 73, 100, 102, 104, 106, 122, 124 and 126), the frame rails must be widened to accept the larger flywheel, bearing plate and flywheel housing. No charging system is required or recommended for a pulling tractor because it'll rob horsepower and add unnecessary weight and extra wiring. Read below for information on how to convert a narrow frame Cub Cadet.

If you want to do away with the old, heavy, battery draining, power-robbing starter/generator on a narrow frame Cub Cadet and install a lightweight gear starter along with the larger 9-1/2" diameter geared flywheel on a Kohler engine, you'll have to widen the frame rails. To do this, with the engine removed, cut a slot halfway down into the frame where the front of the flywheel shroud sits. For the rear cut, measure 17" back from the front of the frame (to where the metal bends for the clutch cover), and then make the cut there. Then using a large pipe wrench or very large Crescent wrench (I found either of these work great), bend or spread the frame rails outward 11" from the front of the frame. Use a (large) flywheel shroud as a gauge to determine how wide the rails will need to be. This will eliminate having to put the engine in and take it out again. Spread the frame 5" forward (towards front of tractor) from where the slot was cut. Check to see that the frame rails are bent upward from spreading out the metal. (Hold a straight edge tool under each frame rail to check for straightness.) If the widening process was performed correctly, then they shouldn't be bent. If they are bent, they will need to be straightened so the driveshaft/clutch will be in correct alignment with the engine. It'll be best to securely weld two full-length 1/4" thick x 1-1/2" wide steel pieces under each frame rail to reduce the chance of bending. Then securely weld a 1/8" thickness mild steel gusset plate (angle reinforcement brace) into each wedge/cut) opening. A Magnum flywheel housing and bearing plate would require a lot more widening of the frame rails to install in a narrow frame Cub Cadet.

Widening the frame rails as mentioned above and then properly welding in the gussets (reinforcement angle braces) shouldn't weaken it. But make sure that the frame is in fact straight before welding in the gussets. Because sometimes it can bend during the process of widening the frame. To prevent the frame from bending overtime when doing ground-pounding wheelies, weld in the gussets on both the inside and outside of the frame. Put down a good bead of weld, too. If the frame is bent, only slightly, this will interfere with the operation and proper alignment of the clutch and driveshaft. The Cub Cadet model 147 is the only narrow frame tractor that came from the factory with widened places in the frame for the large flywheel. This is also the last narrow frame Cub Cadet manufactured before the wide frame models were produced. There's no need to widen the frame rails on a wide frame Cub Cadet (models 86, 108, 128, 800, 1000 and 1200), because the large flywheel and gear starter will clear the rails.

The parts needed to convert a K241-K341 Kohler K-series engine with a starter/generator into a gear starter are as follows:

To install a gear starter on a K241-K341 Kohler engine in a narrow frame Cub Cadet...

  1. The engine will need to be removed.
  2. The frame rails will need to be cut and widened (enough to clear the [9-1/2"] flywheel shroud), and a couple of gusset plates will need to be welded in for strength.
  3. Install the large diameter bearing plate, (9-1/2") flywheel with a starter ring gear and flywheel shroud on the engine.
  4. A gear starter motor will need to be bolted on the side of the engine block. The block will need to have an indention for the starter.
  5. Then there's the wiring, starter solenoid and push-button starter switch that needs to be installed.

But if you prefer to use the starter/generator when pulling, remember this: the generator part require less than 1hp of engine power to charge a fully drained battery. Therefore, if you were to install an OFF/ON toggle switch to turn off the field windings in the starter/generator, this will prevent it from charging the battery. Which will allow the engine to produce more power.

After installing the flywheel shroud and if the hub adapter, flywheel or starter cup screen rubs part of the shroud on one side. This means the big hole in the shroud is out-of-alignment with the centerline of the crankshaft. It needs to be tweaked to put it in alignment. Sometimes I have the same problem with my customer's engines. To fix it, install all the mounting bolts in the shroud, but leave them loose, then place a soft 2x4 board against the shroud, and then hit the board with a big hammer or heavy rubber hammer to force the shroud over until it's centered with the screen. This is the only way I know how to fix it. I don't know how they get out of alignment in the first place, unless it came that way from the factory and haven't been noticed before. Heck, when rebuilding and/or reassembling an engine, you tend to notice a lot of new things about it. It's kind of like painting your own house on the outside. The owner don't notice maybe a cracked window, loose siding, etc., until they get up-close with it.

Installing a 10-16hp Single Cylinder Kohler Magnum Engine in an Older Cub Cadet Garden Tractor -

With the flanges on a Kohler Magnum engine model M10, M12, M14 or M16 block cut off and with a narrow Cub Cadet oil pan installed, the Magnum will install in a spread-frame Cub Cadet with little to no modifications. But it won't fit in a narrow- or wide-frame Cub Cadet, because the Magnum flywheel shroud and bearing plate are too wide to fit between the frame rails, even when the frame rails on a narrow frame Cub Cadet are widened. Therefore, a large flywheel shroud, bearing plate and upper mount gear starter from an older K241-K341 Kohler K-series engine will need to be installed on the Magnum engine and then the Magnum should install in a narrow- or wide-frame Cub Cadet with little to no modifications.


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If you would like to purchase any of the parts or services listed in this website, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO (Missouri) 65203-9136 USA | Phone: 1-573-256-0313 (shop) | 1-573-881-7229 (cell). Please call Monday-Friday, except holidays, 9am to 5pm, Central time zone. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) A-1 Miller's shop is open to the public from 9am to 5pm, including weekends, except holidays. Please call before coming so I'll be here waiting for your arrival. E-mail: pullingtractor@aol.com. Directions to our shop | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. If you're the kind of person who don't trust delivery/shipping companies (mis)handling your high-dollar and fragile merchandise, you can make the long drive to A-1 Miller's shop to personally drop off and/or pick up your carburetor, clutch assembly, engine, transaxle, tractor, etc. "The road to a friend's house (or shop) is never long." (We're planning to relocate to other property with a bigger and better shop so we can provide many more parts and services.) Please click here to place an order.

A-1 Miller's Fully Computerized Stuska Water Brake Engine Dynamometer (Dyno) Service with DPM Data Logger Software!

For performance testing engines up to 200hp at speeds up to 12,000 RPM. The only engine dyno service in Missouri for Kohler pulling engines! Fully operational and 100% accurate, customers can rent dyno time, fine tune and make adjustments or changes to their engines to gain maximum horsepower and torque, and print-out the results so their tractor(s) will be truly competitive on the track. NOTE: A fresh-built engine may not produce full power until it's broke-in. This is when the valves wear-in with the seats to completely seal in the compression. The rings will likely hold the compression, but the valves may leak slightly until they wear into the seats. This is normal for all engines and may take several hours or pulls to happen, then the valves will be able to hold full compression. Lots of pullers tell me after I've built their engines that it seems to pull stronger every time they pull it.

Engine Dyno Rental Fee: $50.00 per hour run time from the moment the engine is started. No setup fee for Cub Cadet engines with a 3- or 6-pin/stud clutch driver. An adapter may need to be needed or fabricated for other makes and models of engines. Only engines with the narrow base oil pan can be tested. Engines with the wide base (tall) oil pan cannot be tested at this time.


To place an order and/or for FREE professional and honest technical assistance and support, please contact:

If you would like to purchase any of the parts or services listed in this website, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO (Missouri) 65203-9136 USA | Phone: 1-573-256-0313 (shop) | 1-573-881-7229 (cell). Please call Monday-Friday, except holidays, 9am to 5pm, Central time zone. If no answer, please try again later. (When speaking with Brian, please be patient because I stutter.) A-1 Miller's shop is open to the public from 9am to 5pm, including weekends, except holidays. Please call before coming so I'll be here waiting for your arrival. E-mail: pullingtractor@aol.com. Directions to our shop | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. If you're the kind of person who don't trust delivery/shipping companies (mis)handling your high-dollar and fragile merchandise, you can make the long drive to A-1 Miller's shop to personally drop off and/or pick up your carburetor, clutch assembly, engine, transaxle, tractor, etc. "The road to a friend's house (or shop) is never long." (We're planning to relocate to other property with a bigger and better shop so we can provide many more parts and services.) Please click here to place an order.

To place an order, please call the number below Ê or send an email with your name, complete and correct postal address and phone number and so I can figure the total with shipping cost and USPS Tracking. For payment options for parts ordered or services performed, or to make a donation to my websites, I accept cash (in person), USPS Postal Money Orders, cashier's checks, business checks, MasterCard, VISA, Discover, American Express (please add 2.5% to the total for the credit/debit card processor's surcharge), Western Union Money Transfer, MoneyGram Money Transfers or Popmoney. (If a part for a specific purpose is special ordered, your debit/credit card may be charged for the full amount or as a deposit right after your order is placed; please do not send your debit/credit card information in email!) Or you can pay me through PayPal. (My PayPal account name is my email address. And be sure to mention in PayPal a description of what the payment is for.) If sending a money order, please include a note in the envelope with your name, complete and correct postal address, phone number and a description of what the payment is for. My mailing address and phone number are below Ê . I'll make a note of your order, and I may have to order some of the parts, which should take a few days to come in, but I will send the parts to you as soon as I have everything in stock after I receive your payment.

IMPORTANT - When sending your part(s) to me for rebuilding or repair, package everything securely so the item(s) won't get damaged in shipping and please include a note in the box with your name, mailing address, phone number (in case I have any questions) and a description of what you want done. When shipping heavy parts, it's best to put a slightly smaller box inside a larger box, to double the strength and integrity of the package. Because the clumsy "gorillas" or incompetent and uncaring workers that work for certain delivery services mishandle the heavy packages and don't care. And when the work is completed, I'll either call or email you an invoice with the total including shipping & handling.

To figure the shipping cost, I weigh the package with the parts, then I go online to the USPS Postage Rate Calculator website. I type in the weight, my zip code and your zip code, then it shows me the prices for various ways to ship the package. I always choose US Postal Service because I believe that's the most fastest, economical and reliable method.

Shipping: (United States and it's territories)
To save you shipping charges, item(s) in a package or cushioned envelope weighing less than 13 oz. is sent by First Class Mail for a 2-6 day delivery. Most packaged item(s) weighing over 13 oz. is sent by US Priority Mail for a 2-3 day delivery. To save you even more on shipping heavy items, I always try to use the US Postal Services' Flat Rate Priority Mail envelope and boxes (if the item(s) can fit inside the envelope or boxes). Some heavy items weighing no more than 70 lbs. is sent by US Mail Parcel Post. Item(s) weighing over 70 lbs. is sent by FedEx Ground. Again, if you're the kind of person who don't trust delivery/shipping companies (mis)handling your high-dollar and fragile merchandise, you can make the long drive to A-1 Miller's shop to personally drop off and/or pick up your engine, transaxle, tractor, etc.

We Ship to Canada and Worldwide -
Item(s) in a package or cushioned envelope weighing less than 1 lb. is sent by US Postal Service Airmail Letter Post for a 4-7 days delivery. Packaged item(s) weighing over 1 lb. and up to 66 lb. is sent by US Postal Service Airmail Parcel Post for a 4-10 days delivery. I cannot use the US Postal Services' Flat Rate Priority Mail envelopes and boxes to ship outside U.S. territories. Item(s) weighing over 67 lbs. or more is sent by FedEx Ground or equivalent services.



We Accept PayPal, Visa, MasterCard, American Express & Discover Credit & Debit Cards
(When placing an order through PayPal, please provide a list of which parts you need.)

To make a payment to me through PayPal, go to PayPal's secure website ( https://www.paypal.com/ ) and click on Send and Request -> Pay for goods or services. Type in my email address, or copy and paste this: pullingtractor@aol.com, the amount and follow the directions. Be sure to mention in PayPal a description of what the payment is for. After you've finished, PayPal will send me an email notifying me that you have made a payment to me for the product(s) or services and amount entered. Then I go to their website and direct PayPal to deposit the money in my bank account. And I will send the parts to you as soon as I receive your payment. But I may have to order some of the parts if they're not in stock, which should take a few days. In that case, I will send you the parts as soon as they come in. PayPal protects your financial privacy and security. With PayPal, privacy is built in. It's a way for you to pay without exposing their financial information.


Coming Soon - Detailed Illustrated Plans on How to Construct a Professional Pull-Back Garden Tractor Pulling Sled, and a Motorized/Self-Propelled Garden Tractor Pulling Sled. FYI - My professionally-built motorized/self-propelled pulling sled, Track Master (click the picture to the right to see a larger image of my sled), is the only one I've ever built and I got it right the first time, with very few changes that had to be made to it. I guess I'm just one of those kind of guys that knows what he's doing. Pullers really like pulling my sled, too. They say it's the best sled they've ever pulled. (Not bragging, just stating the truth.) By the way - Track Master sled is engineered so well (by Brian Miller), that other sled builders/owners have copied my well thought-out and proven design. Anyway, I have lots of work to do in my shop and I work on the sled plans in my spare time. As soon as my plans with an inventory list of parts to use are perfected, I'll post the update in my websites. Remember - Perfection takes time. If it's worth having, it's worth waiting for. Also, I plan to acquire a bigger shop and I may build high quality garden tractor pulling sleds in the future to offer for sale. Please call me at 573-256-0313 (shop) or 573-881-7229 (cell), or email me at pullingtractor@aol.com or pullingtractor@yahoo.com if you're interested. - Brian Miller


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