I bought my 2006 ex250 a few weeks ago, and it had been running fine until today. I started my bike this morning with my choke fully on, and let the bike idle until it was a little warmer, so I let the choke half way out. I started down the road, with my choke still halfway on. About 100 yards away from my house, I turned the choke completely off and continued riding. Everything felt normal until my throttle felt much less responsive than normal. As I pulled up to the approaching stoplight, my bike died. I couldn't get the bike to restart with or without choke, so I parked my bike in a nearby parking lot, walked to my car and drove to school. On my way back from school, I stopped at my bike, started it, and rode it home with the choke halfway on and it felt normal. When I arrived at my house, the bike was even idling at a little under 2 grand without choke, as it should. I checked everything: gas, petcock, kill switch, charged battery, ignition key etc. No aftermarket modifications on the bike whatsoever. what could be happening?