Have a craftsman tractor model 917.259580 with a kohler engine model cv15s, type # ps41525. Started having problems last year. It would run normal for a while then backfire and stop and won't start. After sitting for a couple of hours it would start again run for a little while and stop again. Since then I have replaced the air filter, the gas filter, the carburreator and the fuel pump. Any ideas on what may be wrong? Beginning the think the problem may be the ethanol in the gasoline.

You can also have a burned valve in the engine. Have you tried checking the compression on your engine?

Hi,
Try the ignition coil. Classic symptom of a bad coil is described here.
Peace,
Clarke