I have a 2008 CRF250R, and this bike WILL NOT run. Not with kicking your leg off, not with push starting. Every few kicks it'll backfire out of the airbox and that's all it'll do.
Has new cam chain, hot cam, piston ring.
I have checked, rechecked, reset, rechecked, disassembled, reassembled, and set timing for days and this thing will still only backfire. PLEASE HELP!
Things that have been checked:
Flywheel and woodruff key, no damage to key
Cam chain tensioner changed to manual, its not too tight or loose
Piston ring set right and staggered,
Timing is set to match on right side timing mark, left side flywheel hashes, and cam lobs are back and matched with the top of the head, and TDC was verified while setting.
Valves are within 0.005, exhaust is a 120 and the smallest shim so I can't get it and closer.
Wiring harness replaced, grounds cleaned, connections cleaned, spark plug replaced.
I'm completely at a loss and open to any ideas you guys might have.