Questionfollowing up on your response, the engine has good power and i don't see a significant change in engine rpm as i adjust the carb at high speed. as far as i know there is no anti-backfire solenoid on the carb, but i've never had it completely disassembled. i did notice that this last time the engine now sounds like it may have a head gasket leak. hope this gives you more insight. -------------------------
Followup To
Question -
i have an john deere 214 tractor with a recently rebuilt kohler. the engine starts fine and runs well for about 1/2 hour. then the exhaust starts to sound reedy or sharp, begins to backfire and sometimes has sparks and flames exit the exhaust. the engine is super heated when this occurs and you can't even hold the spark plug in a gloved hand. after it cools off it's fine. i've tried to adjust the carb thinking it was too lean. the old standard 1 1/4 to 1 1/2, then let it warm up, max throttle and set the other adj until engine stumbles and back it back 1/4 turn. what's next?
Answer -
You are correct, this does sound like a lean issue. You didn't mention if adjusting the carb has much effect on the engine's running and power. If it has little or no effect, the carb could have a blockage. When it is running during the first 1/2 hour, does it have decent power under load? Is the carb equipped with an anti-backfire solenoid? If you can provide this information, I may be able to provide some more insight.
AnswerA bad head gaskey can cause a lean condition as well, yes. As well as leak compression pressure, it can also create an entry point for air on the intake stroke. In light of that information, I would recommend removing the cylinder head to inspect the gasket and mating surfaces. Hope this helps.
