I rebuilt my master cylinder a while ago and documented it on my site. I'll post the text here for easy access. Pics are on my site.
It was hell trying to remove the rubber boot. I couldn’t get to the stopper washer so I just pulled the boot apart with a pair of needle nose pliers. Next I removed the stopper washer and then I took out the snap ring. I bought snap ring pliers from NAPA for $15.00 but I couldn’t use them because they were too bulky and cheap. I was able to get the snap ring out with a scratch awl but I knew I couldn’t use that tool to put the new one back in. I later went to Pep Boys where they had the kind of pliers I was looking for. They were the right size and they were of good quality. What’s better is they cost only $10.00.
I had to spray PB blaster inside the MC to loosen up the washer that keeps the piston inside. Also, I had to use a small screwdriver and the scratch awl to separate the washer from the piston because it was so badly rusted. Finally after about 15 minutes, success! The washer was out and now I was face to face with the stuck piston. To do this, I first used the needle nose pliers along with the edge of the MC to create a lever. That worked enough to get the piston out a little way but I needed it to come all the way out.
Out comes the screw extractor set and drill. I drilled a hole in the piston and tapped the screw extractor. All this did was push the piston back in the hole requiring me to pry it back out. I figured I’d try that a couple times and then pull it out with needlenose. What do you know? It worked. Everything came flying out spraying rust and PB blaster all over my desk.
Now it was time to clean up the master cylinder and put it back together. First I sprayed the inside of the MC with Orange cleaning agent. Then I used a round nylon brush to buff it out. It’s extremely important to make sure the inside of the MC is spotless. Next I started to assemble the parts.
First I attached the check valve to the spring. I then put the primary cup over the small end of the spring and pressed those three parts up into the master cylinder check valve end first. If you do this, don’t forget to put a little brake fluid around the inside of the master cylinder and the rubber parts to keep everything properly lubed. Next I wedged the secondary cup over the piston with a small screwdriver and snapped it into place. I pushed the piston in the MC and placed the 10.5mm washer over that. Pushing everything down inside the master cylinder I gently placed the internal snap ring in with the special snap ring pliers. Finally I put the boot down over the piston and secured it with the stopper washer.
That’s it; all done! I installed the rebuilt master cylinder on the bike and bled the brake. It worked flawlessly. It took a lot of patience and the right tools but I have to say it was well worth the effort. Not only because I have a better master cylinder but also because I will feel much safer riding the bike now.
Parts:
Joint bolt washers #90545-300-000 $1.60 ea
Joint bolt #90145-300-010 $4.30
Master cylinder rebuild kit #45530-377-305 $29.00
