I recently bought a bunch of pocket bikes all in good shape but all had some sort of problem. I took the best parts off of them and made one extremely nice bike. The one problem I am having with it is that the chain likes to come off. There is a bolt connected to the back axle that tights and loosens and slcks or tensions the chain. How do I find the "butter zone" where it isn't too loose to come off, and it is too tight to come off? The two sprockets are lined up really well, but they are a little off. Would it be possible that that was the problem? When I say a little I mean like so small its less then 2-3 mm from drive sprocket to driven sprocket.