Hi,I am stuck with a problem regarding a ride on. It is a John Deere D120 with a 21hp B&S motor. Problem, will not turn over on compression stroke,but when I turn the motor back a revolution by hand, hit the key and it will start,plus backfire(only once though). Have been told it could be the internal decompression unit or the valves, or both, having never worked on an engine this big not sure of valve clearence. And would the decompression unit make it backfire, can understand how it mite stop it turning over on compression stroke. Any help or advice is appreciated.
