Looks to me like there is a ding in the edge of the bore where it meets the deck. May need a little Tig weld, bore/hone, and deck. New dome would help if the current ones are showing a mark from where they were set on the deck.
Pilot? If he used it in the trails, getting it wound up to high rpm then letting off the throttle a lot for turns and obstacles, they need a fat pilot to keep lubed when off throttle.
If you want that thing to live, it needs to have the cases split. Metal from the case is no good. Crank is probably toast or at a minimum on borrowed time.
Also. If someone is porting it, you should be getting domes as well.
The 500* stuff I found is silver.
Looks like this. http://m.summitracing.com/parts/the-18101?seid=srese1&gclid=Cj0KEQjw0dy4BRCuuL_e5MeqmNABEiQAq8iNIyOrpx7uuk4TGzYADFJKo1IPPLVJzOPdBP8PBtI6HQQaAmXU8P8HAQ