Ok some background on the bike first. It's a 99 YZ400f that I rebuilt with a 426 crank, piston and cylinder about 2500miles ago. It's a street ridden supermoto, but previous to this it hadn't been ridden in a month or two. This weekend I took it up to Monterey to watch the RedBull USGP. Thursday and Friday it was running great, just like normal. My buddy and I rode from the track, down hwy 1 to Big Sur and back with no problems at all (about 85 miles total). Friday night we went to ride into town for dinner and about 5 miles into the ride I noticed that it was idling really high. When I stopped it was idling around 5-6k rpm. I decided to shut it off to try and find the problem and that's the last time the bike started. Now when you try to kick it over the kicker just stops when you hit the compression stroke, you cant kick through it. It will sometimes do that when it's hot and I shut it down and it cooks for a bit, but never when it's fully cold. What could possibly cause this? Stuck choke? Some seal or o-ring come apart? Idle screw vibrate out? Anything I should look for?