When I started riding the machine the other day I noticed that I had to have the throttle slightly more open than usual to develop similar power. Rode for about an hour. Machine starts to lose power. Feels maybe 40-50%. I had to just about pin it just to to 40Kph. It is also running very loud and making a dud, dud, dud sort of noise. Checked and both cylinders at 120psi. Both have spark. Plugs on the wet side. When I rotate primary by hand, it feels smooth. If this was a problem with one of the cylinders would I still have good compression and should I be able to feel this when rotating the primary? Would I be able to feel a main bearing problem when rotating primary? Any direction is greatly appreciated.