Okay, I'm thinking about buying a used '03 XR 400. However, when I went to test drive the motorcycle, I noticed that the bike would "stutter" when I rolled on the throttle. In other words, if I was driving along at around 35mph and then opened the throttle quickly the bike would hesitate for a split second before taking off. Is this just a jetting problem, or something more serious? If it is a jetting problem, which jet would I need to look at, the main, pilot, needle, etc? This will be my first off-road motorcycle, so I'm kinda new to this stuff....... Thanks in advance for any help!