I just finished putting in a new headgasket and removing the airbox and replacing it with cone air filter, I also did the 1/2 spacer mod, the bike is not starting and after it turns over for a while it backfires and a puff of smoke comes out of the air filter. any help is appreciated

I am guilty of doing too many things at once & then hop[ing it will start. If all you had done was the head gasket & then it wouldn't start it would be asy to figure it was cam timing or something to do with that work. You have kinda sorta "poisoned the well" & can't tell where to get your answer. My knee jerk reaction is the worst news. If it was mine I would be all shook up about the cam timing. Besides, doesn't look loike you did all that much to the carb.

OK, so i figured out that the petcock was set to prime and was flooding the carb hence the backfire, thanks all, it runs now