Stick on a fresh rebuild could be bad communication between engine builder and racer. Builder sets it up thinking it will get a long break in and the customer thinks it’s ready to race.
If I don’t know what’s going to happen to the engine after it leaves the shop I put in extra clearance.
Ignition could be set up with too much advance and too little rotor clearance. Might be a contributing factor.
Did you put oil in the gas?
FAA certified jet engine and aircraft technician,
Nicholson Speedway class champion 2001,
Yamaha KT100 Service Center,
41 years karting experience