Is it possible for the cam gear to slip or turn on the cam? It appears to be pressed on, but I don't know if there is a key on the cam to keep it in place. There is not a key visible from the side. The reason I am asking is the dealer is trying to fix my 98 yz400 and he said this is the only way it could be out of time. When assembled and the timing marks are lined up, the 3 intake valves hit the piston slightly. Any help is appreciated. They want to buy a new cam and gear, but I want to make sure that is the right thing to do.