I have an 05 Dr that has the same problem. I have not got into the carb yet, it is totally stock, but I think that is the culprit. Mine seems to miss and backfire when it is hot. Some of the backfires sound like a gunshot! I ride at altitude here in Colorado, and suspect the stock jetting is the problem. Then again, what the hell do I know? Any advice from those that know bike mechanics would be appreciated.
How timely. I just bought a XR50 for my son's 5th birthday in 2 weeks. He has the bicycle down (even starting to do tricks) and he has a Razor pocket bike that he rides the crap out of. Since he has experience with the throttle and brakes on the Razor I think he will do well on the XR with out the training wheels. I set the throttle and will now have to wait and see.