Similar problem here. Bike was running fine, then after sitting 7 to 10 days, it started fine but quickly started to miss and pop through carb. Well, after rebuilding carb problem was still present. Installed new plugs and it ran perfect...for very few miles and then same thing. Checked the plugs again and they were very sooty. I have fresh fuel, new plugs, and rebuit carb. I suspect a weak spark condition. Any ideas on most likely cause of weak spark? What should I test first and how? Maybe a hotter plug?
Thanks Kev