I have an 03 wr450. I lost compression so I checked the automatic decompression and the exhaust valve is sticking open even after the cam lobe and decompression pin are past it. The bucket looks fine and so does the cam. That day it started great, I went for a little slow ride around the woods tried to hop a log and it ended up being really thick mud. I got it out 15 mins later, and it took for ever to get it to start, seemed to have no compression. Now it doesnt have any and I can see the valve and hear it hanging open. What should I try?