"Rear" Master Cylinder

devilswild66 · #1 10th June 2007

Rear Master Cylinder Woes could there be a service bullentins:

I just put on a new rear tire and did not mess with the rear cailper (MoCo manual says you do not have to remove the rear caliper). After getting it all together and set up my rear brake quit working.

So I tried to bleed the hydraulic system to no avil it did not work. I just disassembled the master cylinder and found the "PISTON SPRING" through the "PRIMARY CUP". Great...now I have to wait for the dealer to get parts in (I have to order)

(Just-in-time inventory is just great

).

chrishajer · #2 10th June 2007

No bulletin or recall for the rear master cylinder that I know of. Most of the problems I see with the rear brakes, after a pad or tire change, are due to not getting the pins and pads installed properly on assembly.

http://www.xlforum.net/vbportal/foru...ostcount770026

That doesn't explain what you found in the master cylinder, but changing the rear tire didn't cause the problem in your master cylinder I don't think. If you didn't pull the caliper or the pins, I don't see what could be wrong back there either.

--Chris

Hot Rod Sporty · #3 10th June 2007

I took my 05 in for a spongy rear brake, and they first said that I needed new brake pads (at 7500 miles). When they put it up on the lift, the rear brake master cylinder was bad and they replaced it (under warranty). They never told me exactly what was wrong with it.

chrishajer · #4 10th June 2007

That would make three that needed repair then, all of the sudden (that I have heard of anyway). CBAS5 just had one replaced too. Not sure what's going on there ...

--Chris

devilswild66 · #5 11th June 2007

Here is a picture of the torn cup...

chrishajer · #6 11th June 2007

That's pretty crazy. Good picture

Any idea how it happened? Were there any pieces missing from it that would have caused something like this?

--Chris

devilswild66 · #7 11th June 2007

All the major pieces are in the picture. Above the primary cup you will see the center section which is a nipple that goes into the piston spring. The last piece is just above the nipple (center section of the primary cup) which is 0.100" x 0.050" x 0.050" in size.

--Chris
I want to "believe" that I felt something different with the brake pedal about one to two months ago, but the brake had been function just fine by stopping the bike. When I pulled the piston spring out of the master cylinder the cup was through the first couple of loops on the spring.

chrishajer · #8 11th June 2007

That's definitely weird. Maybe you did feel something, but we all try to piece together things to make the explanation work. I've never had one of those master cylinders apart which is why I didn't know if all the piece were there.

It almost seems like a piece between the cup and spring is missing, or that something is missing off the end of the spring?

--Chris

CBAS5 · #9 11th June 2007

I had problems with my rear brake for awhile before I took it in. However, mine was more obvious. I would lose brake pressure and then regain it as I rode the bike. Did you see any pieces of something in your brake fluid? I had orange globs in mine.

devilswild66 · #10 11th June 2007

--Chris
I got a new picture that might give better details (3 pics in 1).

CBAS5
I will flush out the system once I rebuild the master cylinder and there is no since in cleaning out the system untill the new kit arrives. I could have globes of stuff in my lines which will get flushed in do time...and my guess is this rebuild kit will not get here till Thursday.