I'm tearing down the top-end for a rebuild on a 96 XR250. I have all the cylinder head cover bolts removed, but have been unable to get the cover off. I suspect this is the first time it's been removed. I've whacked it pretty good with my rubber mallet. I've also used a hammer and block of wood trying to break it loose. I can't get it to move. I've tried heating the cover with a torch, but no luck. I'm trying very hard not to damage the aluminum, or break a fin. I've sprayed the gasket all the way around with PB Blaster a couple of times, but no luck so far. Any suggestions would be appreciated.