Re: Chain bound up in fromt sprocket
this is a serious thing,as you already know the wheel locks up and bike comes to an abrupt stop.
second part of this- the housing around the chain,breaks off.mine broke the magneto housing as well as the clutch lever housing.pretty much demolished crankcase.
make sure the wheel sprocket runs perfectly true,side to side and up-down.
straight edge from sprocket to engine sprocket,making sure its very close.
chain tensioner need be adjusted correctly,using minimum amount of chain.
some here have good success eliminating chain tensioner altogether.
i had a little issue with chain rubbing tire,it was a little too knobby on the sides.i think this was part of the cause too.