I found that some fly wheels are too small and are a pain to bump start I have 2 gt2 one with a traxxas 3.3 pull start and one with a bump start picco 15 the traxxas will pull start and bump start no problem the picco I had to mod the chassie thats were the dremel comes in handy take a little of by the flywheel to get the bump wheel in with no problem.this helped me hope it works for u.