It's been awhile since I posted anything on this forum, but here goes. I've been restoring a '74 Yam TY250 (almost done). Motor is in great shape, no problems at all, just cosmetics. With the motor out I wanted to take a look at the clutch to see how worn it was. When I got it apart I saw these really strange steel disc. I had never seen disc like these before. Looked like someone had ground it a bit on the outside and made it look like a nipple. All the steel disc looked like this, except for the last one . I was told that these were stock disc and it was normal. What I'd like to know is what was the purpose of having them shaped that way?
Thanks