I have a similar problem with mine which started a few days ago. It runs fine above 3000 rpm, and it ticks over ok, but between 2 and 3k it feels like it's missing on one cylinder. I tried new plugs (even though I'd recently changed them) and new caps, but that hasn't fixed it. I might try new coils at some point if it gets any worse, other than that I'll just ride around it for the rest of the summer, and get the carbs professionally cleaned and set up over the winter.