What is the service history like on this bike?
Ever have the top end removed or piston rings replaced?
How do the cam journals look?
Checking compression is a tool that is most applicable to gross interpretations of rebuild faults, imho. If I had any question regarding the service life of the top end I would just bite the bullet and tear it down. I don't really use compression checks as any type of indicator on these new wave four strokes. If there appears to be an issue just pull the top end off of it.
I know I am repeating myself, sorry :bang: