A compression check will probably not show worn valve guides as the valves will probably still seal on the seats.
R bikes have guides that have alot of clearance and no valve seals.
Check into new guides and valves if you find this to be the problem.
Matt at Motor West in Milw. WI. Sells some "tighter" guides and seals. (high quality)
I am sure others sell the same ones.
But give Matt a call.
I can explain it to you, but, I can't understand it for you.