250-500cc 1999 and other years WR250 Rear Master Cylinder Rebuild Kit FOUND!

Like many of you, I was surprised to find that Husqvarna, and more specifically Brembo does not list a rebuild kit for the rear master cylinder on my 99' WR250. They never had one, but for some time you could get the replacement outer boot, though that is no longer available. This master is used on several years of WRs, CRs and on some TEs as well. Brembo refers to this cylinder as a PS12. It is a 12.7MM piston size master.

So before I went and blew good money for a new master, I took this one apart to determine what was the main issue. The outer boot was torn on mine and I did try to source one awhile back with no luck. So the actuator rod, and washer that it must pass through freely was rusted a bit. The piston itself was in good shape. I cleaned all the parts and removed all rust.

I began the process of discovering what other bikes used a 12.7 MM rear master and found the Nissin cylinder used on many Yamahas and Hondas was this size. In fact the rubber boot was exactly the same style. All Balls list a rebuild kit for this cylinder part # 18-1007. I ordered one from Amazon for $13.50. Now I knew not all the parts would be the same however the critical ones were exact or very close. The seals and the boot were the main items I was after. Since my piston was in good shape I only elected to replace the top seal near the spring. The kit seal was the same diameter but slightly thinner. The piston already has a stainless washer under the seal so I found another stainless washer to shim this up a bit and it fit perfectly. I elected not to replace the bottom seal since mine was in good shape and I risked damaging the original without knowing if the replacement would work.

Also one of the circlips in the kit was the exact size as well and the Brembo uses only one. I lubed the parts with fresh brake fluid and reassembled the piston into the cylinder. The most important part for me was the rubber boot. The Nissin style boot was EXACTLY the same and fit perfectly! Before fitting the boot I applied a generous amount of silicone grease around the bottom of the fitting then popped the boot on. After a thorough bleeding session my rear brake is back to working perfectly with no hanging up.

I didn't post a series of pics since the cylinder is so simple and minimal parts. However here is a pic of the finished cylinder so you can see how nicely the bottom boot fits.

So this was a worthwhile experiment for $13.50!

pretty sure Nissin is a license made Brembo

A kdx200h nissin boot fitted perfectly on my 09 wr250.