I have a 20 hp kohler with 900 hours. It has been using oil for a while. I noticed that there was a small leak at the OHV cover just about the spark plug. Yesterday it would not start, so I checked the carburetor to make sure the fuel pump was working. It was okay. I then looked at spark plugs. The front plug was totally gummed up around the outside of the plug around the fins of the cylinder. I replaced plug and it still wouldn't start. A couple of times it backfired while I was trying to start it. I checked the compression and found the bad cylinder to be 120 psi and 150 psi on the other cylinder. If I try to start it, it will hit every once in a while but just cant get started. Any suggestions.