i think i have a 16X10 master airscrew prop. only 15 dollars. and i have a stock ryobi 31cc out of a weedwacker. i trimmed the flywheel by taking everything but the magnets and counter weight and backing because there is no need for the extra weight and resistance from the blades. i noticed some rpm increase. and for the backing plate the plastic just has to get trimmed. it is an easy engine to convert and there are prop hubs and mounts avaiable out there for it. oh this is a biggie... need an 11mm carb with 2 adjustments (high and low). a world of a difference. maybe 1500 with stock carb and a prop. 11mm carb wow...