Important Information About Small Engine Flywheels

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Three types of flywheels were used on the 10hp-16hp K-series Kohler engines. They are as follows:

  1. Very few of the early 10hp and 12hp engines came with a 9-1/2" diameter flywheel with an unmachined edge, but no ring gear for the starter motor, and there's no way to install a ring gear. These engines used 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 pulley that was attached to the flywheel to crank the engine. There is no battery and no charging system involved. These were popular engines for the U.S. Military because there were very few parts to give trouble. The ignition coil is no longer available from Kohler for these models.
  2. Many of the early 10hp and 12hp 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.
  3. In later years, the 10hp through 16hp 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.

And the K-series and Magnum flywheels have the same overall dimensions. The only difference is, the K-series flywheel has integrated fins and the Magnum flywheel uses a bolt-on plastic fan, 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 10-16hp K-series and Magnum single cylinder engines, and the KT-series and Magnum twin cylinder engines.


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

To remove the flywheel from a Kohler (or virtually any) small engine, remember, the retaining nut or bolt have right-hand threads. 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 requires 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 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 NF, 1/2-20 NF and 5/8-18 NF.

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 prybar 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 lawn mower on my work table to remove the flywheel, I noticed that the flywheel was wobbly but still tight on the crankshaft, then I found the crankshaft was broken in two at the connecting rod journal. I thought this was odd , so I called the customer and told him about this, and he said his neighbor tried to "pop" the flywheel off [by hitting the threaded end of the crankshaft] with a 10 lb. sledge hammer!

About Crankshafts Breaking at High RPMS -

A cast or billet steel crankshaft should survive as high as 7,000 rpms for a long time if they've been precision-balanced to the connecting rod and piston assembly. 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 (steel flywheels should be precision-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 rpms. 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 rpms, 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 Heavy [Steel] Flywheel on a Pulling Tractor!

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 cast iron flywheel for the single cylinder 10-16hp Kohler K-series engines with the starter ring gear and full fins weighs 23-24 lbs.

Here's the dimensions if you want to fabricate a 9-1/2" diameter steel flywheel for the 10-18hp 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 flywheel for the 10, 12, 14, 16hp flatheads and the 18hp OHV single cylinder Kohler K-series and Magnum engines will interchange. They all have the same taper in the center, and most of them have two or four tapped holes for accessories, and for using an automotive harmonic balancer/vibration damper puller tool to remove the flywheel from the crankshaft.

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.

And adding a heavy pulley on the PTO end of the crankshaft would help add torque to the engine at high rpms. 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!

NEVER INSTALL A DIRTY FLYWHEEL ON A DIRTY CRANKSHAFT!

Before installing the flywheel on a crankshaft, always use a clean cloth (white in color, to see the dirt) to remove any dirt, oil or debris from the crankshaft taper and most importantly, inside the flywheel taper. Use cleaning solvent (paint thinner) or brake cleaner because these leave no oily residue when they dry. And use emery cloth to remove any light rust. 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 (or driving force) of the piston via the crankshaft. Do not use anti-seize for easy removal of the flywheel later! And there's no need to apply liquid threadlocker on the tapers to install a flywheel to keep it from slipping on the crankshaft. If either of these are used, an acetylene torch will be required 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.


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.


IMPORTANT! IMPORTANT! IMPORTANT! IMPORTANT!
Below are the results of a cast iron Kohler flywheel with a crack in the keyway and/or when spun well above 4,000 rpm (wide open throttle) Ê

The photos below 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 rpms. 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

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

Go here to purchase a nice, in-dash small engine tachometer: Veethree 0-4000 rpm Back-lit Panel Mount Tachometer or here: tachometer proximity sensor | eBay.


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 360° 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.


Torquing the Flywheel Nut or Bolt - 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 wrench either.

But if an air 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 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 side of the block, and allow the Vise Grips to bump against the bolt to torque the flywheel nut or bolt.

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.

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If you need any of the parts or services listed below, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203-9136 USA | Phone: 1-573-875-4033. 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.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. Send a message with Yahoo Messenger: | Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. Click here for more of our parts and services. | NOTE: To place an order, please call or send an email with a list and description of the parts or services you need. Because as of right now, we're not set up to accept orders through our web sites online. Due to the rising cost of... everything, prices are subject to change.
Precision, Dynamic Spin-Balancing Service -
  • Balance flywheel (steel or cast) - $50.00 labor, plus return shipping & handling. & handling..
  • Balance cast crankshaft - $125.00 labor (mallory extra), plus return shipping & handling. To balance an engine, we will need the crankshaft, piston/rings, pin, clips, connecting rod and bearing inserts. The flywheel is balanced separately.
  • Balance steel crank - $150.00 and up (mallory extra), plus return shipping & handling.
  • Regrind Crankshaft Journal - $50.00 per journal. On a twin cylinder crankshaft, $100.00 total, plus return shipping & handling. Note: The 10hp-16hp and the 18hp OHV single cylinder 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 7hp and 8hp Kohler and other makes 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 NF threads in the PTO end of the crankshaft for a retaining washer and bolt. $20.00.
Flywheel Retaining NutAll-Metal Self-Locking Flywheel Retaining Nuts for threaded stud on end of of early K-series and all steel crankshafts. Each torque at 65 ft. lbs. IMPORTANT: For proper torque, apply thin coat of oil on threads of crankshaft before installing nut.
  • For 5/8" diameter stud (5/8-18 NF). $1.50 each, plus shipping & handling.
  • For 3/4" diameter stud (3/4-16 NF). $1.75 each, plus shipping & handling.
Flywheel retaining bolts for threaded hole in end of later K-series and all Magnum crankshafts. Each are grade 8, 1-1/2" long. IMPORTANT: For proper torque, apply thin coat of oil on threads of bolt or inside hole before installing.
  • 3/8" diameter, fine thread (3/8-24 NF). (Torque at 40 ft. lb.) .50¢ each, plus shipping & handling.
  • 5/8" diameter, fine thread (5/8-16 NF). (Torque at 65 ft. lb.) $1.00 each, plus shipping & handling.
Steel Rectangular Flywheel Key for early Kohler K-series engine models K241, K301, K321 with the 8" diameter flywheel. Dimensions: 3/16" wide x 1/4" tall x 1-3/8" long. OEM Kohler part # X-366-1-S.
  • Used. $1.00 each, plus shipping & handling. (When available.)
  • New. $2.25 each, plus shipping & handling.

Aluminum Rectangular Flywheel Key for Kohler K-series engine models K141, K160, K161, K181, K241, K301, K321, K341, K361 and Magnum M8. Made of 6061 alloy; medium-grade hardness aluminum. Dimensions: 3/16" square x 1-3/8" long. Replaces Kohler part # X-366-1-S.

  • $5.00 each, plus shipping & handling.

Steel Square Flywheel Key for Kohler K-series engine models K141, K160, K161, K181, K241, K301, K321, K341, K361 and Magnum M8. Dimensions: 3/16" square x 1-3/8" long. Kohler part # X-286-17-S.

  • Aftermarket. $1.00 each, plus shipping & handling.
  • OEM Kohler part. $1.50 each, plus shipping & handling.

Aluminum Square Flywheel Key for Kohler K-series engine models K141, K160, K161, K181, K241, K301, K321, K341, K361 and Magnum M8. Made of 6061 alloy; medium-grade hardness aluminum. Dimensions: 3/16" square x 1-3/8" long. Replaces Kohler part # X-286-17-S.

  • $5.00 each, plus shipping & handling.

Steel Woodruff Flywheel Key for early Kohler engine models K160, K161, K181 and later 10-16hp K-series and all Magnum engines. 3/16" wide x 1" long. Kohler part # X-46-3-S.

  • Aftermarket. $1.00 each, plus shipping & handling.
  • OEM Kohler part. $1.50 each, plus shipping & handling.
Flat washer for retaining flywheel or aluminum clutch hub to flywheelExtra Thick Steel Washers for retaining flywheel and/or Cub Cadet aluminum clutch adapter hub to flywheel. A must to prevent hub breakage! Available in 3/8", 5/8" or 3/4" diameter center hole x 1-1/4" o.d. x approximately 1/4" thick. $3.00 each, plus shipping & handling. (The 3/8" washer is the same used for the solid motor mount kit.) Steel Adapter Step-Washer for mounting Cub Cadet aluminum clutch hub with 5/8" center hole to Kohler Magnum crankshaft with a 3/8" bolt. A must to center hub and prevent hub breakage! $8.00 each, plus shipping & handling.
Used OEM Aluminum Clutch Drive Hubs with either a 5/8" or 3/8" center hole. $20.00 each, plus shipping & handling. (When available.) 1/4" Steel Dowel Pin for aluminum clutch hub. 3/4" long. Secures above hub to flywheel to prevent slippage. $1.00 each, plus shipping.

Removing the Majority of the Fins from the Flywheel to Reduce Drag on Engine -

One sure way to increase the power output 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 pulling competition, the flywheel will still provide plenty of fresh air to sufficiently cool the engine. This shouldn't be done on an engine for general yard work only because the engine could run hotter than normal, causing premature wear.

How to Remove the Fins -

A 14" chop saw, like the one that most automotive muffler shops use, can be used to remove the majority of the fins from the flywheel. To cut the flywheel fins off with a chop saw...

  1. First of all, wear eye protection or safety glasses and a surgical mask to keep from breathing in the cast iron and cutting wheel dust particles.
  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 requires less effort to rebalance.)
  4. To spin-balance the flywheel, a 1-1/2" diameter x approximately 24" long 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.

Then without a doubt (and using common sense), any flywheel with the majority of the fins removed should definitely be dynamically precision spin-balanced using 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 the 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! Go here to purchase a nice, in-dash small engine tachometer: Veethree 0-4000 rpm Back-lit Panel Mount Tachometer or here: tachometer proximity sensor | eBay.

Or better yet, install a billet steel flywheel and an electric fan to cool the engine.

Advertisement:
If you need any of the parts or services listed below, please contact A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203-9136 USA | Phone: 1-573-875-4033. 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.) Fax: 1-573-449-7347. E-mail: pullingtractor@aol.com. Send a message with Yahoo Messenger: | Directions to our shop | Yahoo! Maps, 1501 W. Old Plank Rd., Columbia, MO | 1501 West Old Plank Road, Columbia, MO - Google Maps or Map of 1501 West Old Plank Road, Columbia, MO by MapQuest. Click here for more quality parts and services | NOTE: To place an order, please call or send an email with a list and description of the parts or services you need. Because as of right now, we're not set up to accept orders through our web sites online.
Used 9-1/2" diameter genuine OEM cast iron Kohler K-series flywheel for 10hp-16hp K-series flathead and 18hp OHV 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 fins and no cracked or missing internal magnets for charging system (if used for yard use). These flywheels are for stock tractors only; not to be turned above 4,000 rpms!
  • 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 fins 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 fins 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 fins and precision rebalance. $85.00 labor, return shipping extra. Includes cutting most of the fins off, chuck it in our lathe to true up the fins so they're all even and then balancing it.


Cooling the Engine with an Electric Fan -

Using a steel flywheel with no cooling fins will, without a doubt, allow any engine to operate at a much higher temperature. If you're burning methanol fuel and full synthetic motor oil, they'll help keep the engine somewhat cool, but the engine will still run hot from lack of a cooling system. Excessive heat will cause an engine to lose power and eventually "wear out." Therefore, installing an electric fan to cool the engine, especially between pull-offs, wouldn't be a bad idea. Pulling tractors that have a smaller engine (8hp or 10hp) usually don't go very fast down the track will really benefit from an electric cooling fan. Acquire a quality fan that can handle a lot of vibration, and mount it securely!

One type of fan that works great for cooling a pulling engine is the Attwood Turbo 3000. It measures 3" in diameter x 5" in length, draws 2.6 amps, and has 145 cfm air flow. It can be securely mounted on the clutch cover or between the grille and PTO end of the engine and aimed toward the exhaust area of the engine, because that's the hottest part of any engine. The Attwood Turbo 3000 is available on eBay and from other places. Return to a previous page or paragraph.

Because this fan draws power from the battery, which could weaken the spark for the engine, use an electric only to cool the engine after a pull, while driving the tractor around, or between pull-offs. And if the cooling fins on the engine block are clean (free of debris), if the throttle shaft isn't worn in the carburetor, if the ignition timing is set at 20 degrees BTDC, and if there's plenty of air blowing over the engine, then it should operate at a cool temperature.


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, it's not necessary to heat it. Instead, place the flywheel with the fins facing upward on a steel top work table or bench, use a 2-3 lb. hammer to remove the ring gear. Gently tap evenly around the entire gear to avoid warping or bending it. It should eventually fall off.
  2. Position the other flywheel face down, and lay the ring gear on it with the beveled edge of the gear teeth facing upward. (This allows the starter gear teeth to engage more easily.)
  3. Use an oxy-acetylene torch to heat the ring gear 360° to expand the steel so it'll install on the new flywheel. Once 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. NEVER hammer a [cold] ring gear onto the flywheel! Doing this will bend it badly out of shape and ruin it for use.

By the way - the same flywheel ring gear fits the Kohler K-series and Magnum 7hp through 18hp OHV single cylinder engines and the aluminum block/cast iron cylinders twin cylinder engines. The flywheel itself on the 7 and 8hp engine is different. It's taper that fits on the crankshaft is smaller.


Differences in Kohler's flywheel
  shroudsWidening a Narrow Frame Cub Cadet for Use of a Large Flywheel and Gear Starter -

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 10-18hp 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.

Widening the frame for use of a large flywheel & gear starter 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 equivalent, 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 would need to be. This will eliminate having to put the engine in and take it back out again. Spread the frame 5" forward (towards front of tractor) from where the slot was cut. Then weld a gusset into each wedge (or cut) opening. Use 1/8" thickness mild steel to widen the frame rails. A Magnum flywheel housing and bearing plate would require a lot more work to 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 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.

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 10-16hp Kohler K-series engine with a starter/generator to a gear starter are as follows:

But if you prefer to use the starter/generator when pulling, remember this: the generator part requires 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.


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