Originally Posted by merryman

You can see the cam if you take the followers out, now you have the cylinder off. Turn the crank round and see if the cam is going round as well. If it is, the chain isn't broken. As I wrote above, marks on the side of the piston are piston seizure, due to either oil shortage or getting too hot. We do 350s so often we have a rebored spare cylinder with piston, so we can take the seized ones off and pop a rebored one straight on without waiting for a new oversize piston to come, and then getting the cylinder bored to match it. Many times the bike has oil in it, but we can tell by the smell and dry rockers, that the owner has filled it up again with oil, after he seized it. Also check the fan works, in case this is the cause of overheating, and that oil is getting to the rockers, once rebuilt. Warning, it takes ages for oil to get there when you are spinning the engine over on the starter.