OS .91 FX engine lacks compression
 

OS .91 FX engine doesn't seem to have much compression when the prop is turned
by hand, and it only flips halfway and makes an odd clacking noise. It starts
up okay and runs smoothly, but I'm wondering about the unusual way it acts
when just flipping the prop. Maybe a bad piston ring or ??????
Any ideas? Many thanks! Ollie 707-538-1855 Santa Rosa, CA