Mine was very lumpy and really didn't like being below 4000 until I did the starter valve sync like in the thread above and it made a huge difference. It's still not great below 3000 rpm but I think thats just too low for these bikes no matter what, maybe the carbureted bikes are better at really low RPM. It also made the throttle response a lot smoother, it was very twitchy before and was really difficult to smoothly apply throttle at low speed. I also removed the pair system and flapper but I'm not sure that did anything.