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:
- 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, 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 to the bearing plate and a rope was used on a large pulley that was attached to the flywheel to pull-start 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. The engine had battery-powered ignition, and a small, gear type starter 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 hammer to remove a flywheel! 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 the above 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
has 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 - I once had a customer bring his lawn mower with a Tecumseh engine to me just remove the flywheel. When I was working on it, I find that the crankshaft was broken in two at the connecting rod journal. So I called my 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 my 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 24 lb.
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. Make the surface for the ring gear on the flywheel .015" - .020" bigger than the i.d. of the ring gear itself. 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 steel 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 flathead engines and the 18hp over head valve single cylinder Kohler K-series and Magnum flywheel will all 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 a gear puller 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. 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 a flywheel
on the 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. 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. This is very, very
important! 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 an aluminum key or with a steel key, would 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.
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 another [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 required mainly for a safety reason.
Click Here To See the Results of a Cast Iron Kohler Flywheel When Spun Well Above 4,000 RPM.
When the flywheel nut or bolt
is tightened or torqued down, the "squeezing" action of the flywheel taper
actually "grips" it to the crankshaft, guaranteeing positive metal to metal
contact, with no slip. 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 nut is self tightening. Therefore, a lockwasher isn't
necessary. But sometimes the nut will wear out and tend to loosen over time.
When this happens, the keyway in both the flywheel and crankshaft will become
damaged beyond repair. Therefore, a new locking nut is required for a rebuild.
But use a split lockwasher on the bolt.
The best type of flywheel key to use in virtually any engine is soft aluminum (4041 hardness). The reason for this is if the connecting rod in an engine breaks resulting in instant engine lockup, the soft key will prevent damage to the flywheel. The aluminum key will shear, allowing the flywheel to slip on the crankshaft, preventing damage from either the flywheel or crankshaft. 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 for the flywheel. The only reason Kohler engines (and a few others with camshaft-driven ignition points) uses a flywheel key is to align the flywheel to the crankshaft for the ignition timing degree marks, and not to prevent the flywheel from slipping on the crankshaft.
Advertisement:
| If you need any of the services performed or items listed
below, please contact me, Brian Miller, at A-1 Miller's
Small Engine & Specialty Shop (1501 West Old Plank Rd., Columbia,
Missouri. 65203 | Phone: 1-573-875-4033). Please call any day between 12
noon and 8:00 p.m. Central time, and please be patient because I stutter.
Fax: 1-573-449-7347. You can also contact me through Yahoo! Messenger:
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 Flywheel retaining nuts for threaded stud on end of crankshaft.
Self-tightening jam nuts. Guaranteed to stay tight!
Available in....
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 Flywheel retaining
bolts for threaded hole in end of crankshaft. Grade 8, 1-1/2" long.
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 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. |
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 Steel adapter step-washer for mounting the aluminum clutch
hub with a 5/8" hole to the Kohler Magnum crankshaft with a 3/8" bolt. A
must to prevent hub breakage! $8.00 each, plus shipping.NOTE: I can also custom machine other adapter washers to fit your particular application. All I need is the dimensions. $10.00 each, plus shipping. |
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 Used
OEM Aluminum Clutch Drive Hubs with either a 5/8" or 3/8" center hole. $20.00
each, plus shipping. (When available.)
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How to Reinstall Loose Magnets Inside the Flywheel -
First of all, the magnets needs to be polarized. This means the North and South ends of each magnet must placed N-S-N-S-N-S, etc. To find the North and South ends of the magnets, tie a string around each magnet and allow it to dangle in midair. The ends should face the North and South of the earth. (Use a compass to find true North.) Then mark each magnet and the rest you can figure out. Use contact cement to adhere the magnets to the flywheel.
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. This is why most race cars don't run a fan blade. 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!
Personally, I 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 I chuck the flywheel in my metal
lathe to true up the fins so they'll all the same height. And then I ALWAYS
have my 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 me, Brian Miller, at
A-1 Miller's Small Engine & Specialty Shop
(1501 West Old Plank Rd., Columbia, Missouri. 65203 | Phone: 1-573-875-4033).
Please call any day between 12 noon and 8:00 p.m. Central time, and please
be patient because I stutter. | Fax: 1-573-449-7347. You can also contact
me through Yahoo! Messenger:
Balancing Service -
You can also have your flywheel and crankshaft/piston/rod assembly professionally dynamically precision balanced at:
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Cooling the Engine -
Using a steel flywheel with no cooling fins will without a doubt allow an 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 some what cool, but the engine will still run hot from lack of a cooling system. Excessive heat will cause an engine to lose power, too. 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 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 can be mounted
between the grill 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.
Another fan that works great 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, at your local Bass Pro Shops (or order online) and from Midwest Super Cub. Return to a previous page or paragraph.
And I'm not sure what the temperature should be on a Kohler engine. I 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 the Tractor Frame for Use of a Large Flywheel and Gear Starter -
The larger 9-1/2" diameter flywheel with a starter ring gear,
larger bearing plate and 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, 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 more information on how to convert your narrow frame tractor.
The parts needed to convert a Kohler K-series engine with a starter/generator to a gear starter are as follows:
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If you want to do away with the old heavy, battery draining, power-robbing
starter/generator on a narrow frame Cub Cadet (models 70, 71, 72, 73, 100,
102, 104, 106, 122, 124 and 126), 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.
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.
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
me, Brian Miller at A-1 Miller's
Small Engine & Specialty Shop (1501 West Old Plank Rd., Columbia,
Missouri. 65203 | Phone: 1-573-875-4033). Please call any day between 12
noon and 8:00 p.m. Central time, and please be patient because I stutter.
Fax: 1-573-449-7347. You can also contact me through Yahoo! Messenger:
|
||
Used 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!
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 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.]
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 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.]
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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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[Non-Pulling Information Below]
Converting the old starter/generator charging system to the newer, alternator-equipped charging system: First off, all of the 10, 12, 14, 16 and 18hp single cylinder Kohler flywheels will interchange. The crankshaft tapers are the same. They're the same weight, too. The stator-type charging system will also work on a narrow frame Cub Cadet, but the frame must be widened to accept the larger diameter flywheel, bearing plate and shroud. The larger bearing plate will accept the stator/charging ring. And you'll need an electronic voltage regulator that's capable of handling the amount of amps that the stator produce. Stators come in 15, 25 and 30 amp output. But the 15 amp ones are the most common. To identify the amount of amps a stator produces, the 15 amp one have 18 posts, but only 16 are used (wrapped with wire) and has 2 wire leads (or connectors). The 25 amp stator have 18 posts, all of them are used and has 2 wire leads. The 30 amp stator have 12 posts, which are wrapped heavily with wire and have 4 wires leads. If you use a regulator made for a smaller [amperage] output, it'll burn up in no time. Remember, the higher the amperage of a charging system, the more power it'll draw from the engine (when under a severe load). For wiring diagrams of various Cub Cadets, see this web site: http://www.ihregistry.com/ref/wire.htm.
Linked pages to my parts & services:
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