High RPM Backfire when fully warmed

Huh? Not true at all. Timing mark in the bend is light for max power/efficiency
how is it not true and then good for one setup? do you know what his build is? how would it be not true if we don't know the setup? We are looking for examples that lead to his issue. For a max power and efficent engine, the timing could be better...


I will add that timing is NOT the main issue right now, but it could be better. The issue looks like fuel, that plug looks like it could be practically new or not idling much.