1992 john deere 425

[Loganjohndeere425]

Started her up this afternoon heard a snap and lost compression on the right cylinder. Pulled the valve cover and rockers aren't moving but left side has loads of compression? What could be the cause??

 

[oldnslo]

Plastic cam gears are a known failure point on certain years and models of the Kawasaki engines used in Deeres. Hopefully that snap wasn't piston hitting a valve.

 

[Zebrafive]

My JD 285 had the plastic cam gear fail. It was when starting the engine (engine failed to start). Mine lost 7 teeth in row on the plastic cam gear, so the cam was no longer rotating when I cranked the engine. IIRC these engines are ones the valves do not hit the pistons.