The valves seem spot on still, so no idea there. Maybe I can take a shot at seeing if it is the timing chain. Just interesting this was never a sound before the valves were adjusted, but also before the valves had no gap at all.
As far as neutral goes is beyond me. I can sit there with the clutch in while running (F/R switch engaged) just fine. If the bike is off and F/R switch engaged either direction, I can not start it without it trying to pull forward (or reverse), nor can I just pull in the clutch and push it while off. Both starting and pushing the thing requires the F/R to be in the middle. I have found neutral (using the shifter) a few times but they were all accidental and random (maybe 5 times total). The quad never came with the Neutral/reverse light bezel. I did however purchase one and installed it with no luck. The lights worked when putting external voltage to them, but when installed and hooked up to the correct wires, they never worked. Took my trusty DMM to the leads as well and seen no voltage. I took the bezel off. Seems like unless it is running, the clutch has issues.