Son's 2008 YZ250F. Here's the story, Completely rebuilt top and bottom end over a year ago. 5 weeks ago, kept stalling at Glen Helen. Finally would not start. 4 weeks ago took it to a shop (friend) started and ran fine. Went to Comp Edge and rode all day. This Thursday and Friday night kicked it all night would not start. Kick 10-12 times, rest, go back and kick again. Get a loud back fire and that's all. Sat night it started once and ran but stopped and won't start again. I know it can't be fixed over the internet but any suggestions (well most) will be welcome. What I have tried: New stator New coil New plug Replaced CDI Unplugged neutral sensor Checked/unplugged kill switch Continuity check all wires and connectors Never see a spark with plug removed and gnded Disassembled carb and reassembled Shimmed valves, none were out of spec, three of five were boarder line. New clutch basket and hub (not related but just a mention). Can the flywheel go bad? It took a beating when the motor blew and has some shallow gouges on the inside. I see it is two pieces pressed together with a raised strip on the outside for the pick-up pulse generator. There seems to be four magnets inbetween the peices, can feel them with a steel bar as I slide it around the inside diameter. My son is so bummed. Can't ride for weeks. Can't sell a bike that won't start.