Important
Information About Small Engine Flywheels
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- Widening a Narrow Frame Cub Cadet for Use of a Large Flywheel and Gear Starter
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Three types of flywheels were used on the 10hp-16hp K-series Kohler engines. They are as follows:
- 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.
- 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.
- 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.
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! Besides, the crankshaft could break or crack because it's made of somewhat brittle cast iron, too. And DO NOT attempt to use a wrecking bar (crowbar) to "pry" the flywheel off the crankshaft! And never use a large gear [2 or 3 jaw] puller to remove a flywheel. Doing any of these things could break or crack the crankshaft and possibly crack the flywheel or break it in half.
The Correct and Safe Way to Remove a Small Engine Flywheel -
To remove a flywheel from a
Kohler (or virtually any) small engine, remember, the retaining nut or bolt
have right-hand threads. To remove the flywheel, it's best to use a 1/2"
impact wrench (with a large capacity [minimum 30 gallon] air reservoir tank)
and a quality-made automotive harmonic balancer/vibration damper puller tool
that has fine threads. (This works every time for me.) A harmonic balancer
puller requires two, 3/8" diameter, grade 8 bolts to literally pull or "pop"
the flywheel off the crankshaft taper. Be careful not to damage the threads
on the end of the crankshaft! Although some flywheels are stubborn to remove,
just remember, it'll come off. It's not made onto the crankshaft.
On smaller engines such as Briggs
& Stratton and Tecumseh, it's best to use a flywheel knockoff tool to
remove the flywheel. You can get one at virtually any place that sells small
engine parts, and they come in 3 different thread sizes: 7/16-20, 1/2-20
and 5/8-18. It threads onto the end of the crankshaft and using a prybar
to provide support under the flywheel, you sharply and squarely hit the tool
with a medium size hammer to literally knock the flywheel free from the
crankshaft. And to prevent from damaging the threads in the tool and on the
crankshaft, thread the tool all the way on the crankshaft, and then back
it off 1/2 turn.
By the way - we once had a customer bring his lawn mower with a Tecumseh engine to us just remove the flywheel. When we were working on it, we find that the crankshaft was broken in two at the connecting rod journal! So we called the customer and told him about it, and he said that his neighbor tried to "pop" the flywheel off with a sledge hammer!
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 rpms 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 rpms 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 rpms, 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 9-1/2" diameter OEM cast iron flywheel with the starter ring gear and full fins for the single cylinder 10-16hp Kohler K-series engines 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:
- Overall diameter is 9-1/2".
- Total thickness is 2.250" (2-1/4").
- Diameter of the machined edge where the ring gear fastens onto is 9.250" (9-1/4").
- Degree of taper is 3.575º (most common) or 7.15º.
- Distance of inner taper to backside edge of flywheel is .875" (7/8").
- Length of taper is 1.375" (1-3/8").
- Diameter of small end of taper is 1.0625" (1-1/16").
- Distance from small end of taper to the edge where the ring gear butts up against is 1.71875" (1-23/32").
- Width of keyway is .1875" (3/16").
- When installing the ring gear on the flywheel, I'm not sure what the interference fit should be, but the normal rule of thumb is .001" per inch of the i.d. of the ring gear. This means that the surface for the ring gear on the flywheel should be .015"-.020" bigger than the i.d. of the ring gear. But make it somewhat large to begin with, and if the ring gear has trouble fitting, it can be turned it down .005". This rule applies to all flywheels.
If the above dimensions are somewhat confusing, then perhaps it's best to acquire a Kohler flywheel and measure everything on 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.
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 or oil from the crankshaft taper and most importantly,
inside the flywheel taper. Use cleaning solvent if you must. And use emery
cloth to remove any light rust or scale. Clean both tapers thoroughly. This
is very, very important! 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. Any oil or dirt trapped in or on the tapers will allow the
flywheel to slip or rock back and forth, in which will shear the key, will
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 uses
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.
A cast
iron flywheel with a crack in it, even a small one, 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 was welded,
and when the flywheel is installed on the crankshaft, and the nut or bolt
is torqued, the taper would still split next to the weld. But steel flywheels
don't crack (or break).
A crack in a flywheel will make an engine vibrate severely, plus it'll be noisy. (It'll make a "clunk, clunk, etc." 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.
Click Here To See
the Results of a Cast Iron Kohler Flywheel When Spun Well Above 4,000
RPM.
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 to 65 ft. lb., and the 3/8" bolt to 35 ft. lb., but do not overtorque
it! (As with an air impact wrench.) And Kohler's flywheel [castle] nut is
self tightening. Therefore, a lockwasher 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 self-tightening jam nut is required
for a professional repair. But use a split lockwasher on the bolt. And use
a grade 8 bolt, nothing less.
The best type of flywheel key to use in virtually any small engine is soft aluminum (4041 hardness). 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.
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 USA |  Phone:
1-573-875-4033. Please call any day, 9am to 5pm, Central time. If no answer,
please try again later. (When speaking with Brian, please be patient because
I stutter.)  Fax: 1-573-449-7347.
 E-mail:
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|
|
|
 Flywheel retaining nuts for threaded stud on end of crankshaft.
Self-tightening jam nuts. Guaranteed to stay tight!
Available in....
|
|
 Flywheel retaining
bolts for threaded hole in end of crankshaft. Grade 8, 1-1/2" long.
|
|
 Steel flat washer for retaining flywheel and/or aluminum Cub
Cadet clutch hub adapter to flywheel. A must to secure flywheel and to prevent
hub breakage! Available in 3/8", 5/8" or 3/4" diameter center hole. 1-1/4"
o.d. x approximately 1/4" thick. $3.00 each, plus shipping & handling. |
|
 Steel adapter step-washer for mounting the aluminum clutch
hub with a 5/8" hole to the Kohler Magnum crankshaft with a 3/8" bolt. A
must to prevent hub breakage! $8.00 each, plus shipping &
handling.NOTE: We can also custom machine other adapter washers to fit your particular application. All we need are the dimensions. $10.00 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.
How to Reinstall Loose
Magnets Inside the Flywheel -
When a magnet comes loose inside the flywheel, it can be Super Glued back in place. But first, be sure to thoroughly clean both the flywheel and magnet (use brake cleaner or cleaning solvent (paint thinner) to dry out any oily residue), and make sure that the poles of the magnet(s) are in the right postion. North-South-North-South-North-South-North, etc. To find which poles are north and south on the loose magnet, tie a string around the center of the magnet and allow it to dangle in mid-air. The poles will attract to the natural magnetic poles of the Earth. Then write on the magnet which poles are which. Then, when installing the magnet in the flywheel, be sure the poles are opposite of each other. If they attach, it's in the right position. Go here for more information on this subject: Flywheel Magnets.
Removing the Majority of the Fins from the Flywheel for Added Power -
One
sure way to increase the power output of an engine is to reduce the amount
of drag that the flywheel fins cause. To do this, you'll need to remove the
majority of the fins from the flywheel. The flywheel will still provide plenty
of air to cool the engine, too. And then
definitely have the flywheel dynamically precision balanced, and do not spin
it above 4,000 rpms!
Personally, we use a 14" chop saw, like the ones that most auto muffler shops use, to remove the majority of the fins from Kohler flywheels. Then we chuck the flywheel in our metal lathe to true up the fins so they'll all the same height. And then we ALWAYS have our flywheels dynamically precision balanced!
Or better yet, install a machined steel flywheel. But make sure that the steel flywheel doesn't have no more than 4 short cooling fins on it, or little will be gained in power. If fins are installed on a steel flywheel, make sure they're welded- or bolted-on very securely with at least grade 8 bolts! A flywheel with full fins (and no operating governor) will allow an average engine to rev up to about 4,500 rpm. But depending how an engine is built, a flywheel with few or no fins will allow an engine to rev up anywhere from 6,500 to 9,000 rpm.
Advertisement:
| If you need your crankshaft and piston/rod assembly and/or flywheel
precision dynamically balanced, please contact A-1 Miller's Performance
Enterprises | 1501 W. Old Plank Rd. | Columbia, MO 65203 USA |
Phone: 1-573-875-4033. Please
call any day, 9am to 5pm, Central time. If no answer, please try again later.
(When speaking with Brian, please be patient because I stutter.)
Fax: 1-573-449-7347.
E-mail:
pullingtractor@aol.com. You can
also contact us through Yahoo! Messenger:
Precision Dynamic Balancing Service - To balance a rotating assembly, we need the crankshaft, piston/rings, pin, clips, connecting rod and bearing inserts. The flywheel is balanced separately.
|
Cooling the Engine -
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 In-Line Blower, (part # 38-560-424-00
[4" diameter]). It's 5" in length, has 145 cfm air flow, and can be mounted
on the clutch cover and aimed toward the exhaust area of the engine. These
are available on
eBay and
Midwest Super Cub.
Another fan that works great for cooling a pulling engine is a 12 volt computer cooling fan. Although an ordinary computer fan will work well, a high-performance fan, such as the Vantec 92mm Tornado Fan, will work even better. Most computer fans are small and compact, and on a Cub Cadet, can be mounted between the grille and PTO end of the engine, and be sure to aim it toward the exhaust area, because that's the hottest part of an engine. The Vantec 92mm Tornado Fan (part # TD9238H) that's pictured here, measures 3-13/16" x 3-13/16" x 1-1/2", weighs 6.6 oz., draws 1 amp of power, has 119 CFM air flow, turns at 4,800 rpms and the motor is supported by double, precision, high-speed sealed ball bearings. But the fan will need to be wired separately from the ignition (and fuel pump) circuits. If the fan operates while the tractor is pulling, engine vibration could damage it. Use it only to cool the engine between pull-offs. They're available on eBay and at most local computer parts supply stores. Return to a previous page or paragraph.
And we're not sure what the operating temperature should be on a running Kohler engine. We do know that if the cooling fins on the block are clean, 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 have to acquire
a used flywheel with a good ring gear on it.
- With the flywheel facing upward, use a large hammer to remove the ring gear from the flywheel. Tap gently and evenly around the entire gear to avoid warping or weakening the [ring gear] metal.
- Position the other flywheel face down, and lay the ring gear on it with the beveled edge of the gear teeth facing upward.
- Use an acetylene torch to heat the ring gear and it'll eventually drop down on the flywheel. This will expand it so it'll install on the new flywheel with ease. Do not hammer the gear onto the flywheel! Once in place, allow it to air cool.
By the way - the same starter ring gear fits the 8hp, 10hp, 12hp, 14hp, 16hp and the OHV (Over Head Valve) 18hp single cylinder Kohler K-series and Magnum engines. Only the 8hp flywheel itself is different. It's taper is smaller.
Widening 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.
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:
- Large diameter (9-1/2") flywheel with a starter ring gear.
- Large diameter bearing plate that's designed for flywheel above and a K-series gear starter and charging stator.
- K-series flywheel shroud for flywheel, bearing plate and starter above (for either an upper-mount or lower mount gear starter).
- K-series gear starter. (Lower mount for 7-8hp engines, and lower mount on the 10-16hp engines if the gas tank is in the way - not for Cub Cadets. Upper mount only on 10-16hp engines for Cub Cadets.)
- Starter solenoid (if your particular tractor/equipment requires one).
- Charging system (stator and solid state voltage rectifier/regulator).
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.
Advertisement:
| If you need any of the items listed below, please contact
A-1 Miller's Performance Enterprises | 1501 W. Old Plank Rd. | Columbia,
MO 65203 USA | Phone:
1-573-875-4033. Please call any day, 9am to 5pm, Central time. If no answer,
please try again later. (When speaking with Brian, please be patient because
I stutter.) Fax: 1-573-449-7347.
E-mail:
pullingtractor@aol.com. You can
also contact us through Yahoo! Messenger:
|
||
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!
|
||
 Used flywheel shrouds for
Kohler K-series 10hp-16hp K-series flathead engines with the 9-1/2" flywheel
and the upper mount gear starter. These are in good condition, not damaged,
cracked or rusted out. $35.00 each, shipping included within in the
Continental U.S. if purchased separately. [When available.]
|
 Used large aluminum
bearing plate for the 9-1/2" flywheel and battery ignition on 10hp-16hp Kohler
K-series flathead engines. These are in good condition, not damaged. Comes
without bearing and oil seal. $35.00 each, shipping included within
in the Continental U.S. if purchased separately. [When available.]
|
|
All the parts needed to convert your 10hp-16hp single cylinder
Kohler K-series flathead engine from the small flywheel with the
starter/generator to the large flywheel with the ring gear starter.
The flywheel is for stock tractors only; not to
be turned above 4,000 rpms! Includes the following parts: [When
the used parts are available.]
NOTE: These are the older K-series flathead engine parts, not Magnum. All used parts are in excellent condition. And if you have a narrow frame tractor, the frame rails MUST be spread or widened for these parts to fit. Because there's no other way to make them work. And this conversion kit is meant mainly for pulling tractors. |
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