My Poulan 42cc from a Craftsman saw turned a MA 18/8 at 7980 RPM steady. Have a WT289 carb and a G10 carb block I made for it. Didn't even taper the cylinder side. Could probably get away with a little bigger carb as the formula for carb size I made on Excel indicates a little over 12 MM size at 8000 RPM.