the throttle stop keeping the butterfly from closing is not going to have an effect on the max rpm’s from the motor. While you have the air cleaner off, check that the butterfly is opening completely. Also check that the throttle pedal stop will not allow the throttle to try to get past full open. That will put undue stress on the carb. Are the other carb settings now the same as when you sent the engine in?
LAD Specialties customer / tony kart / rotax / kt100