I have a '91 superjet (650cc) with no engine mods. I seems like over the past summer, the ski had lost a significant amount of power. It runs great. No idle or starting problems, but just has very low power output throughout the powerband. I checked the compression last night and it came up with 120psi for one cylinder and 125psi for the other. I'm not sure what the compression is supposed to be. What could be wrong?