2004 Yamaha Blaster Starting Issues?

[Paige P]

Just put a new top end on my blaster. Rode it easy for about an hour just letting the power bands kick breaking it in. It backfired a few times and died. Put new plug in and can barely get it to start. It may run a couple second at the most, and it backfires when kicking it sometimes. I took the head off and the piston looks fine with no cracks and still fits tight. There was alot of oil in the head that I cleaned off and it seems to fire a little better. It's getting spark and fuel but I think it's a fuel issue. Also the gas was mixed way to rich, it was 8 ounces to a gallon and it was usually ran at 4 ounces per gallon. I drained that gas and put fresh in it but I think there was sytill oil settled in the tank. Any solutions or things I should try.. Thanks