Nice bike!

I'd start by removing the exhausts and taking a look inside the cylinders to see what the condition is like inside, look for scouring and blow by. If it looks clean inside, great. Next, with your exhaust off, get your power valves set to HRC specs, as per the workshop page. This is most likely the cause of your problem.

Yes, you have to take your exhausts off if you want the power valves to be adjusted properly.