Thank you all for your advice and insight. I decided to order a new crankcase cover since it was also damaged. For the damaged area on the actual crankcase, I’m going to fit a piece of metal and JB Weld it into place. I’ll use a dremel to shape it so the crankcase cover will seat well. Hopefully that will work. Thanks again!
My son and I are restoring a 1986 XR100R and as we got into disassembling the engine I found damage to the left side of the crankcase. The attached pic isn’t mine but one I pulled from the internet. Apparently I’m not the only one with this problem. The mating surface between the left crankcase and the crankcase cover has a chunk missing. There’s no way to seal off the flywheel area when the crankcase cover is installed. Any suggestions? I’m assuming it can’t be repaired. Anybody ever buy one half of a crankcase and installed it? What kind of job is splitting the crankcase and putting it all back together correctly? Should I just look for a new crankcase or a whole new engine? Kinda bummed out about this I appreciate any advice you might have.