I recently purchased a new CRRC 50cc engine and I can't get this thing to start no matter what I try. I have been flipping that prop for two days now and I think I am about to just give up. I have tried everything I have read on these forums and nothing has worked so far.

I know it is getting a spark because I removed the plug from the engine, hooked it up to the wire and checked it. I have tried all of the priming methods I have read about. I have tried using just the choke and I have tried putting my thumb over the carb and spinning the engine until a little bit of fuel runs out. I also checked the needles and they are set according to the "manual"(which is nothing more then a few pages of safety instructions).

The only thing it will do is backfire. It has probably backfired about 15 times in the past two days and then the prop spins off and I have to start all over again. What should I try next? I have a sledgehammer standing by.