This is just to show the easiest and effective way I have found to install the rear caliper dust seal. Everything else to do with a caliper cleaning and rebuild can be found in fog's front caliper service thread. https://www.ex-500.com/37-how-s-fyi/1...r-service.html
The rear caliper dust seal is much more superior to the front one. It is the reason why the rear caliper piston stays much cleaner than the front one. Thus having to do maintenance on it not near as important as the front. The only draw back being, it is more difficult to install.
The seal needs to be seated not only on the inside of the cylinder, but also on the outside of the piston.
Keep the seal and piston lubed with brake fluid. Put the seal on the piston from the back side, the side opposite of where the brake pad will later go. Make sure you put it on in the proper direction, the smaller inside diameter side of the seal goes towards the seating side of the piston.
Slide the seal all the way to the opposite side of the piston of where the seat area is. What we're trying to do is get the part of the seal that seats in the cylinder off the piston while keeping the other part on. This is to make it easier to get the seal seated in the cylinder.
On the part of the seal that seats into the piston, turn it inside out, while keeping it on the piston. Now you can get the caliper seating side of the seal about 1/4 inch off the piston. While still keeping a fair amount on the piston.
This is the tricky part. Now take the piston with the seal on it and fit the seating ring into the cylinder. This part can take a little patience and effort. If something goes wrong, and you get the piston stuck in the cylinder, and you have to get it back out to start over. You can get it back out by applying compressed air to the hole where the banjo bolt goes. BE ADVISED
this will shoot the piston out like a bullet. It could probably take your finger off, if it is between the piston and the caliper "legs".
Once you have the seal seated in the cylinder, all you have to do is push the piston in easily and the part of the seal that was earlier turned inside out should seat in the piston and turn right side out by its self.
In the end this is what it should look like.