Rear master cylinder

[frankd]

Haven't been riding the 89' much the last couple of years because of all the eye surgery I've had.     Today the Mrs. and I went for a ride, and after using the brakes about 5-8 times, the rear pedal went almost all the way down.     I stopped and looked for an obvious brake fluid leak, but everything was dry.      After getting back home, I noticed that if you pump the rear lever a few times, you got some pedal.     This says to me that there was air in the brake lines.    I haven't had a chance to verify this because the bike needs to cool down, but how would a lot of air get into a system that had a firm pedal before.     The only thing that I could figure was the master cylinder leaked air when I released the brakes.

I pulled the right side tupperware  and saw no wet spots, but there was crud over part of the master cylinder.     Also the reservoir was filled normally about a month ago, but now I can see no fluid when I look down into it.     The bolt for the front brake line is tight.     

Any ideas??

Frank 

 

[Vickersguy]

You've got a leak.  That white crusty stuff in your picture is dried brake fluid.  The up side is you have a master cylinder that looks to be in good condition.  The rebuild kits are on e-bay for a reasonable price.  Pull it, clean it, soak the circlip in oil for a day and free it up.  The rebuild is a breeze. XXX steel will used gently will smooth the corrosion, if any, on the inside.   A small wire brush will get the big stuff on the outside. Check the tube to the reservoir for leaks, check the o-ring on that black plastic spigot the hose connects to.  Clean carefully, degrease, blow it out with compressed air and paint with rustolium or some such to protect the aluminum. You'll be good to go. You can reuse the copper seals by heating them  bright orange and quenching them quickly in cold water.  Let us know how it goes ! 

[Vickersguy]

It occurred to me that you might check the rear brake caliper also.  Its hidden and your leak might be there.

[cimmer]

It is also possible if you havent change out the brake fluid in the past number of years, you might have some moisture in the system and just need to flush some fresh fluid thru the whole system. Dont forget the the left front rotor and caliper is part of the rear brake system also with an additional bleed located up near the triple tree. Check the service manual on the correct bleeding sequence for the bike. 

Hope this helps.

Rick F. 

[frankd]

Thanks!

I ordered the rear master rebuild kit and it should arrive in a few days.     I replaced the brake fluid in the clutch system about a month ago.     I should replace the fluid in the brake syster also.      I'l have to bleed the rear system anyway because of all the air pumped in, I'll just push the calilpers back and get that old fluid out.      

Frank