Small Engines (Lawn Mowers, etc.): I have an 416 Allis Chalmers..., allis chalmers tractor, kohler engines

Question
I have an 416 Allis Chalmers tractor w/42''deck after mowing for about 5 to 10 min. It will start to stall like it is over loader.  I have replaced all bearings in the mowing deck, coil, rebuilt carb.does not burn or throw out oil It has about 1500 hrs runs smooth until hot then starts giving problem bring to idle shut off blades let idle runs smooth restart blade runs ok for about 50' starts all over again.   16 Horse power Kohler engine

Answer
CARL, I HAVE VERY LITTLE KNOWLEDGE OF KOHLER ENGINES.  IT SOUNDS TO ME LIKE THE BLADE CLUTCHING ASSEMBLY MIGHT BE THE CULPRIT.  IF YOU NEVER ENGAGE THE BLADES AT ALL AND JUST TOOK OFF DOWN THE ROAD IN HIGH GEAR SHE'D RUN FINE?  THEN IT HAS TO BE SOMETHING LIKE THAT.
I WISH I COULD BE OF MORE HELP TO YOU.
GEORGE