20hp Kawasaki twin cylinder. Engine runs perfect for about 20 min. then will instantly start to spit, sputter, & puff black smoke. If I shut off deck & idler back it usually recovers. Start mowing again, then it will continue to happen on & off. It might run fine for 5min. or 20min. but continues to act up. Seems to set it off by going on an incline. Action so far, rebuilt carb & adjusted float. Tried to duplicate by removing one plug wire but it doesnt act the same.
Any help would be greatly appreciated, Thank you! Farmboy