Not sure if you watched my Big Bear playlist but I have explained the rear brake in a previous video. It's older so the quality isn't great. Its near the end of this video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-BVEtjjnT_CU.html.
I have a 1993 model and I believe the hub (the large nut needs to come off to take the hub off) is a little different from the one you have. Do you have a method of bleeding the front brakes (mine has the original fluid and could use a flush). Have you replaced the front brake flex lines on yours? Do you have a parts source you use?
As for parts, I source it either from Yamaha or my local Royal distributing. My brake bleeding procedure is to 1. make sure the reservoir is kept full 2. pump the pedal or level and hold 3. open the bleeding screw until it stops flowing and close it before releasing pressure. There are tools available but I find this method works just as well. Also, believe it or not, my flex lines are original. Hope this helps
It's really not much. I can probably get away with a 1/2 inch spacer. Maybe even some washers but I really don't want to widen it out. It's fun to pass newer bikes cause they just don't fit
