Originally Posted by
ps2fixer
FYI, you don't need TDC on a single cylinder, you just need both valves 100% closed, so compression stroke works too =). Also there's two timing marks on the fly wheel, but since it's a 4 stroke you have to check if it's on the right cycle or not for TCD vs between exhaust and intake cycle.
In the two videos it sounds like a slight knock at the right rpm, guessing that's probably the timing chain though. Seems pretty loud and didn't change much with the valve adjustment.
I think you can take the "CDI" cover off and pull out the pulse generator and the next cover to see the cam gear and check if the chain is tight or not. Haven't really messed with that exact model of engine much though. I'd think you could put a socket on the cam bolt and move it back and forth to see the chain slack when the valves are closed (compression stroke). If all is good, there should be little to no play before the crank moves, if it's sloppy you'll want to change the timing chain. Some engines are an interference engine meaning the piston and valves can come in contact with each other, other engines are non-interference where it doesn't matter if the chain jumps timing. Guessing the engine probably is an interference engine though. You can get by for a while with a loose chain, but it's a grenade waiting to go off.