Could someone, maybe, please help me with my old reliable Case lawn tractor. Its a sturdy Case 446 with a Onan B43M motor. I have had it over 20 yrs. and I am a very capable mechanic. Rebuilt the motor 5 yrs ago. Ran great until last year, until it developed a bad surge..,I rebuilt the carb..., and got thru the year. Now.. no surge (purrs like a kitten at idle), but power fad and spitting at full throttle. Won't run with load on (mower deck). Re-checked carb float level and high speed jet (good and good)(fine mist coming in) just wants to conk out unless I play the choke. Govener is not stuck and seems to play along with the throttle. Any Ideas.., Thanks