I have a Noma 10/27 snowblower with a Tecumseh motor. I have used it 3 times this winter and had no problems until tonight. It started up all right but when I put it in reverse to move it I heard a big clunk sound and then the engine quit. When I pull the engine over it turns over very easy by hand. Took the spark plug out and doesn't feel like any compression. I see the valve inside moving up and down and my spark plug firing. I used electric starter and it sounds like it wants to go but just won't. Any ideas?