fouled plug on only one cylinder, need help please
 

Rebuilt a Kohler Command 20 (first time, lots of help from YouTube) over the winter. Tractor fired right up and ran fine until about two months ago. Started burning a little oil. Last week it started smoking A LOT and lost quite a bit of power. Pulled both plugs and did a compression test.

Left cylinder, plug dry as a bone, 150 psi
Right cylinder, plug was COMPLETELY covered with carbon, 130 psi

Is 150 to 130 that much of a difference?
The fuel to air ratio can't be off because only one plug was fouled, correct?

Any advice would be greatly appreciated.

fouled plug...
 

Did you replace the coils when you rebuilt the engine? Sounds like one coil is firing erratically (going bad) causing the carbon build up. :bigthink:

Try disconnecting the plug wire on the right side to see if the engine runs with the opposite cylinder connected. Then, pull the wire on the left side leaving the other plug wire connected. The side that runs rough or not at all is likely the problem due to a bad coil. Sometimes the engine will backfire if the coil is bad due to carbon build up (not good for the muffler).

My CH 18 did the same thing. Going to tackle the problem in the fall as I have other projects in the pipeline.

Good luck with your CH20! :biggrin2: