I'm working on this Kodiak 400, unknown history. It has spark, carb is clean, good compression, valve clearances are spot on, fresh fuel, valve timing is very close( looks about a half tooth off). The fourwheeler turns over fine and almost starts, but rarely does. Using the choke and a little bit of throttle help, but it will never fully fire off to an idle. I was able to get it running once and it will rev mid rpm ok as long as you stay on the throttle. As soon as you let off it will die. It occasionally back fires through the carb and seems to mist fuel back into the air box. My initial thought was valve timing or clearance, but they both check out. I can't believe half a tooth of timing would cause this. I am beginning to wonder if the flywheel key is sheered and I'm waiting on a puller this afternoon. Any additional thoughts and suggestions would be appreciated.