XR200 Won't Turn Over after Replacing Piston

My neighbor bought a used 2001 XR200. We recently replaced the piston and rings and reinstalled everything. However, once we got the valve cover and all other parts back in place, the bike would not kick over. We removed the valve cover and double checked to ensure that we were on TDC and put everything back together again. Still no luck...it seems when we tighten the cap bolts down on the valve cover, it locks up the cam. We also referred to the manual and the cam is installed with the lobes facing down, as it appears to be in the manual.

Any thoughts on why this might be happening? :naughty: Is it possible that the cam chain is too tight/loose? Is it possible that the cap bolts are too tight? We are planning on pulling the motor out and taking everything apart again to check everything, but I figured I would check here first to see if anyone has any insight.

Thanks in advance for any assistance!

Are you sure that the engine is frozen up solid? Did you replace the stock piston with a high compression piston? You might try removing the spark plug and see if it will kick over.

I didn't order the parts, so I'm not certain that he ordered a high compression piston (although, I'm guessing that it is). We did have the plug out when trying to kick over. It seems we can kick it about half a stroke and then it locks up. After that, you can't kick it any more. Before we put it back together, we could turn the cam by hand. However, it seems that once we put the valve cover back on and tighten everything, that's when it locks up.

The first thing that cames to mind is the cam gear isn't lined up with the TDC on the flywheel. Second, never put the motor back in the bike, without rotating it via the flywheel with the spark plug out. If you used the kick starter to crank it and something hits, you can bend a valve real easy. You just have to slowly turn the motor over and when it stops, figure out by feel what's stopping it. It sounds pretty obvious, but thats what you have to do. Usually it's something pretty simple.

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