MWSC FAQs: Single Cylinder K-Series Kohler Engines

Posted by Devin Daniels on Aug 08, 2019

What’s the pin height of each piston?
0.750” pin height pistons for the V-Twin
0.875” pin height pistons for the 1 Cylinder K-Series
On the 0.750” pin height pistons, Oil Rail Supports are used to support the oil ring as it passes over the wrist pin area. These are installed with the dimple on the Oil Rail facing downward and located in the wrist pin area.
The Oil Rails don’t touch anything and therefore won’t wear out, so they don’t need to be replaced when installing new rings. (Oil Rails are also used on the 0.875” pin height pistons for the 1 Cylinder K-Series.)

What length connecting rod do I need if I’m running a K-Series 12-16 HP factory piston?
5.300”

What is the stock pin height for a 1 Cylinder K-Series?
1.700” for the 12, 14, and 16 HP. 1.620” for the 10 HP and the 18 HP (Model K361). These both require a 5.300” connecting rod with a stock crank.
A 1.125” pin height piston requires a 5.875” connecting rod.
A 0.875” pin height piston requires a 6.125” connecting rod.
These combinations will bring the piston flush with the deck of the block.
If you want to pop the piston out a certain distance then order the corresponding rod. (Example: If 5.875” is flush, then 6.000” connecting rods would pop it out 0.125”.

How do I install a starter ring gear on the flywheel?
Simply heat the ring gear up with a torch (or put it in the oven) until hot. Then drop ring gear on the flywheel with the chamfer on the ID facing downward.
To remove the starter ring gear, use a punch and tap it off, or use an air chisel.

How do the “internals” (pistons, rods, and crank) differ between the Kohler 10, 12, 14, and 16 HP?
The 10 HP piston has a compression height of 1.620”. The rod (when measured from the center-line of each hole) is 5.562” in length. The crank has a stroke of 2.875”, and the wrist pin size is also different.
The 12, 14, and 16 HP pistons have a compression height of 1.700”. The rod (when measured from the center-line of each hole) is 5.300” in length, and the crank has a stroke of 3.250”.
The 10-16 HP Kohler blocks all have the same deck height 8.625” (when measured from the center-line of the main bearings to the top of the block). Our crank trigger bracket is made for two different bolt patterns; the larger pattern is a bolt circle of 5.625”, and the smaller pattern is 5”. The crank trigger bracket holes won’t line up with these blocks, so you can either drill and tap the block or modify the bracket if you have room.

On a 1 Cylinder K-Series Kohler, which direction does the rod cap go on the MWSC rod? And do you use a bearing?
Either the ½” dish cut, oil hole in rod cap, or thin side goes toward the cam. The longer bolts go on this side as well. (In other words, the thin side of the rod goes toward the cam.)
All of our rods are made for use with a rod bearing, we offer: Standard, 0.10, 0.20, and 0.30 under.

On a 1 Cylinder K-Series Kohler, what is the minimum valve clearance to the head?
0.030” to 0.050”

Is a 10 HP (connecting) rod different than 12-16 HP engines?
Yes. The 10 HP rod length is different, 5.562” long and has a smaller wrist pin of 0.859” (the others are 0.875”).

What size socket goes on the MWSC rod cap bolt?
A 5/16” 12 point socket, which you can easily pickup at Sears, Matco Tools, or SnapOn. MWSC rod bolts are torqued to 20 ft-lbs and are typically engraved on the rod.

For a stock or stock altered tractors, what should the plug gap be set at?
Start at about 30-35, not terribly important where. The gap can vary from 0.010” to 0.075”. We’ve tested a number of different plugs and they don’t seem to make any difference on the dyno.

I received my MWSC Rotating Assembly for a 1 Cylinder K-Series Kohler and my counterweights aren’t marked. Does it matter what weight goes on what side of the crank?
No, the crank doesn’t know the difference; just make sure the weight clears the cam.

Will the MWSC steel flywheels accept the stock charging system?
No, the stock charging system is not needed for tractor pulling or racing.

What’s Sr’s best advice when it comes to attempting an engine build?
Sr likes to “dummy assemble” every engine he builds. This helps eliminate error and repeated steps. Here’s some quick steps to follow:

Install the crank stick and bearing closure plate
Put a light coat of oil (or assembly lubricant) on the bearing surface
Remove rod cap (Pay attention to the cap bolt location)
Install the chamfered rod bearing (We recommend putting a light coat of oil on the backside of the bearings to ease assembly.)
Oil the freshly honed bore (Note: No rings are needed at this time.)
Rotate the crank stick so the journal is all the way up, aka “top dead center”.
Slip the piston and rod into each bore (Remember: Thin side toward cam)
Spin crank stick to bottom dead center, and install rod cap.
Tighten the 5/16” 12 point bolts to where they’re snug (Torque spec not needed yet)
Check connecting rod to cylinder clearance using a cutoff wheel
Degree your cam, or at least check the timing marks if using the cast crank and cam.
Check all other clearances (at least the ones listed below):

cam lobe to connecting rod
cam lobe to lifter
cam lobe to counter weight
connecting rod side
crank stick end play
valve to cylinder head
cam end play
gap rings to piston manufacturers specs

After all measurements are confirmed and everything seems “happy”, take it all apart and clean each part for final assembly.

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