Does anyone know if this series JD has had many engine problems. I have a friend who's 2006 L120 engine crapped out with only 80 hours. The repair shop told him those engines were junk with many problems and short life. This engine just quit and won't run. Turns over really easy like blown head gasket, bad valves, hole in piston, or something like that. Haven't taken it apart yet. Just wondering if this engine is a bad design like the shop is telling us? If the engine has problems does anyone know what typically goes wrong?