I bought a 2003 dr650 with low miles(5000). Bike ran fine at first but then i started experiencing a jerk and then a popping sound out of the muffler while accelerating. I'm wondering if that has anything to do with the carb? The bike was purchased at 800ft of alttitude and i currently have it at 3000 ft. Now it is doing it a lot more. I adjusted the valves, changed the plugs, and changed the oil. It went away for a while but now its back. Any info would be greatly appreciated thanks.