oil

The head of my bolt is stripping I’d like to get a new bolt before taking it out

Hey guys, i recently bought a second hand 1999 WR250 2 Stroke (has YZ250 top end and WR250 bottom end) and i was wondering if i could run full synthetic oil in my fuel? it says in the Manuel that i should run YamaLube 2-R which is full synthetic and ive been running semi-synthetic. Really hope...