This bike has a front master cylinder that is integrated into the Magura throttle assembly and a rear Brembo master cylinder. All three calipers are Brembo F-08 series with dual 38 mm pistons. I disassembled both master cylinders and inspected them. I repainted and rebuilt the rear master cylinder using a Brembo rebuild kit. Unfortunately, I found the front Magura master cylinder bore and internals were badly rusted and pitted, so I had to replace the front master cylinder rather than rebuild it. Even though I didn’t have to rebuild the front master cylinder, I show how you rebuild it and the rear master cylinder in this document.
I also put together two short videos showing the work I did on the front and the rear master cylinders.
1983 R100RS Disassemble & Inspect Front Master Cylinder
1983 R100RS Disassemble, Inspect & Rebuild Rear Master Cylinder
I removed the brake calipers when I removed the brake system and you can see how to remove the calipers here:
I disassembled all three calipers, inspected them and found they were not corroded or pitted so I repainted and rebuilt them using a Brembo caliper rebuild kit. The same kit is used on all three calipers. You can see how I did that work here:
I also put together a video about how I rebuilt the calipers.
1983 R100RS Disassemble, Inspect & Rebuild Brembo Brake Calipers