Mine is dong exactly the same thing and I am a bit baffled. Additionally during downshift I throttle down and I hear the carbs spitting (for lack of a better term). I have played with the carbs to no avail. I just did a big bore and cams and starting to think I may be off a tooth especially since there does not seem to be a way to advance or retard timing. I had a fair amount of play in the chain and in playing I did try another tooth and the mark was still just about where the manual says. Any thoughts on this possibility.
