Well I'll tell you something.I just overhauled an onan last week.It would smoke alittle for 2min and quit for 10 min and smoke again.I was told that it had vacuum leak.Replace the o-ring at the bottom oil tube, and also at the top,don't forget to check rubber hose which operates the fuel pump from vacuum off the engine.Put a vacuum gage on the engine while its running.Try That