My rear master cylinder is losing a few drops of brake fluid each day, and my rear brake could definitely be more powerful. I was curious to know if anyone had used the rebuild kit that is available for these bikes. If so, how were the results?

Additionally, I see that there are 2 kits available: 12mm Magura and 13mm Magura. Can someone tell me which one would be the correct fitment for my 1987 K100RS?

Thanks!