As title states. I have a 2000 fourtrax 300. Compression is at 190 and has a bright blue spark. Just cleaned carb thoroughly and plug is wet with fuel. I noticed when starting with the choke the air box flexes like its building pressure. Sometimes it appears gas is coming out air box. I was thinking tight intake valve, but at TDC they were both loose. My next thought was timing jumped, but with 190 compression i didn’t think that was the issue.

The more i think about it im thinking sheared flywheel key or possibly jumped a tooth on timing. Any inputs or ideas of how to narrow this down? any way to check flywheel key short of removing shaft and fly wheel cover?