I have replaced the points, condenser, air filter, spark plug, fuel filter and carburator (brand new) and this engine just won't run right. It starts up right away, but if I take the choke fully off, it will surge constantly. I can also hear sputtering/very small backfires in the carb. It seems to be blowing out the carb a bit too...like pressure coming out of it when I take the air filter off. I have pulled the head, and the cylinder looked ok, so I think the rings are good...and it doesn't burn oil. The valves didn't look warped, and I adjusted them per kohler spec. This all seems like a majorly lean condition...any thoughts? This is an engine that I have only this experience with. It is on an older allis chalmers. I forgot to mention that cutting grass under load it seems to smooth out the surging problem??? wierd.