My kohler 25 command on my ZTR 1999 with 250 hours went from the usual noisy valves to a internal chattering that killed the engine after 15 min of use yesterday. air cleaner good - oil level just below full. Where do I start. I tryed starting it and engine turns but doesnt start. I then turned fly wheel and heard a faint sound of what sounded like a broken part inside engine. I took valve cover off and valve lifters went up and down on both sides. Of coarse busy time of year. What do I do next? Not fun pushing a dead hydro system even after dumping relief valve on hydralics.