I am working on a 2002 DRZ 400e for my boss. He has been complaining that every time he hit a bump the thing would stall. The last two times he went out the bike stalled in the exact same spot. We thought it was electrical at first, but then thought it was not getting enough gas. I checked the petcock, and been through the carb. I put everything back together, now I can't get it to start. It will start for a few seconds, but when I let off of the started button it dies. Any ideas?