I have a 2001 WR 426 that is YZ timed and that the rings were just replaced about five hours of ride time ago. The bike has been sitting for a few months but I've started it up every week or so to keep it in shape. Because I'm in high altitude in Peru, (9000 feet) I had some problems with plug fouling. I changed to a 38 pilot and it seemed to fix the problem, however a few times the bike has intermittently lost compression and then gained it back. I checked the decompression cable and actuating lever on the cylinder and it seems like everything is working fine. However now there is a clunking sound that eminates from the right side of the engine after the kickstarter has gone through it's stroke. It's almost like the crank is reversing it's direction......probably couldn't do that though! Definitely sounds like something is much more loose than normal. I checked the valve lash and it seemed good, however would the lash be different if the bike is now YZ timed? Could anyone describe what the symptoms are for a crank failure.