I have a Honda GX620 (GCARK-1111412 type QAFX) that got overheated, made the cam gear brittle and it broke. I replaced everything that was a plastic gear (oil pump, governor) with new OEM parts except the camshaft. I used a generic version, but matched up to the old and everything looked to match. Got it all buttoned up, filled with fresh 10W-30 synthetic oil, and new oil filter. It was a little hard starting the first time, but did finally catch and ran fine for a 1-1/2 hour mowing session (this engine is on a Grasshopper ZTR). Got it back in the garage and was ready to mow this week, but again had hard-starting issues. Took the air filter off, gave it a little starting fluid, and no joy, not even a pop. As I kept playing with it, I started getting backfires out the carb and the elbow into the carb was wet with gas. I've deduced that I have an intake valve stuck open.
But this it the part that puzzles me - when cranking the engine over, there is no rocker/valve movement. If I rotate the engine by hand in the reverse direction, the valves open and close as expected. My first fear was the cam gear broke again, but not possible if the valves open 'in reverse'. What am I missing here? Thanks in advance for your help.