A buddie of mine has a 2000 wr400 that was running fine on a Yz timing. After about a 80 mile poker run we stop to take a break and when he tried to start it the motor made horrible noise. He shut it down to see &%$#@! and tried it again and it was locked up. Upon checking on it later he had dropped one the keepers that hold the cam shaft in place when he changed timing.He fixed that with a new keeper. The wr ran great for the next poker run, but did the same thing again. He pulled the valve cover to see if it was the same thing but it was not. When he checked the timing he said that the intake side jumped time. He reset the timing and kicked it over a few times and the timing jumped again. Anyone out there that can offer some advice.