MY MOTOR ONLY RUNS FOR SHORT PERIOD OF TIME BEFORE IT BOGS DOWN. IT WILL STAY RUNNING BUT I AM LIMITED ON POWER. I CAN VARY SPEEDS BUT ONLY SLOW SPEEDS AT FULL THROTTLE. IT RUNS GREAT IN THE DRIVEWAY BUT NOT GOOD UNDER LOAD. I HAVE CHANGED THE FUEL PUMP, SPARK PLUGS, REMOVED FUEL FILTER INCASE...