I have a 50cc gio and I think the timing chain may have jumped a tooth. A little screw broke off in there and was easy to fix but the valve is tapping against the piston, not enough that it did damage but you can see a slight mark on the piston and also it has much less power than it used to. The last time it was running there was a tapping noise coming from the engine as well. How do I check that the timing is right.

 

There should be a mark on each sprocket that needs to be lined up. If you jumped a tooth, it shouldn't be hard to figure out which one needs moved. My experience is with smaller Hondas. Should be able to loosen the chain and get it back on the right tooth. Make sure they are still lined up when you retension the chain. Zero backlash on the gears, but not too tight. You'll probably have to take the plug out so the compression doesn't kick it past where you need to be. Hope this helped some.

Denny