Master Brake Cylinder Revision

[Ben Geutskens]

After cleaning and reassembling the Rear master Brake Cylinder of My XS 1100 FS, the rear brake still did not disengage and became hot. I decided to replace all seals and pads. I am not sure if the rubber pistons were placed correctly in the first place. The blue arrows show the direction of the open ends. Is this correct? What is the thin washer for the new set is provided with? See red Arrow. The photograph shows the revison set at the bottom and the Original old set at the top. The spooge hole has been cleared by the way.

[Ben Geutskens]

There seems to be a problem with uploading the photograph, but the link is OK. Please copy and paste in your browser.
http://www.mijnalbum.nl/index.php?m=fto&a=73&id=372338944&key=LYQOTQQH"]http://www.mijnalbum.nl/index.php?m=fto&a=73&id=372338944&key=LYQOTQQH

[DGXSER]

Hi Ben,

The cup type seal that goes about the middle of the plunger, the large end goes toward the spring side, the smaller end goes toward the C-clip retainer.

The small thin washer goes on the end, covers the star fish looking plate there. The other rubber seal, more open looking one, goes on next with the open end toward the spring. Then the metal cap goes on the tip for the spring to set on.

As to the brake not disengaging, did you also pull the piston out of the caliper and remove the rubber o-ring seal? The way the calipers work is that the piston moves out it also "rocks" the square o-ring seal in its groove. When you release the brake, that o-ring rocks back pulling the piston with it. Over time, dirt and grit accumulate behind the o-ring, especially when they are left to sit for a long time, preventing it from rocking all the way back. So it does not fully disengage the piston or the pads from the rotor. So you need to pull the piston out, remove the o-ring, and clean the groove REALLY well. That will let the o-ring seat in the groove and may solve your problem.

[Ben Geutskens]

Thanx a lot.
This means that the old configuration was correct (I also noticed the metal washer).
Because I wanted to see what the general condition of this newly acquired bike was, I dissembled, cleaned and assembled the brakes (all of it). There was oxide behind the O-rings . I thoroughly scraped the grooves out with a copper hooked scraper which I made. The old O-rings were temporarily put back. Front brakes appeared to work fine. Not the rear brake. Hope it will be better after I have fitted new O-rings (and braking pads, seals, etc).
All brake parts are being renewed now, front and rear.

[IanDMacDonald]

Hey Don- What are the odds that the caliper o-ring can be re-used? I disassembled mine but did not pull the o-ring as I did not have re-build kits. Just cleaned them out. The pistons were a bugger to get back in.

[Ben Geutskens]

Maybe due to oxide build-up behind the rings?

[IanDMacDonald]

Quite possibly. The calipers are still off awaiting my S/S lines to come back. So, if need be, I'll buy some rebuild kits unless those o-rings can be bought individually.

[DGXSER]

Personally, I have not yet bought a caliper rebuild kit. I just re-use the same O-rings, not been a problem for me.

Ben, are you certain you cleaned the return opening in the rear master cylinder well? Got all the crap out of the cylinder in the MC? That return hole (commonly called the "spooge" hole on planet XS11) can be tough to get to.

[Ben Geutskens]

I stuck a thin copper wire through the spooge hole after I read about it on our Forum, but not before. Hope all the things I did help now. Will know soon when I test ride. I appreciate all the help I get from you guys.

[Ben Geutskens]

DGXER,
Still difficult to decide which seal is which.
One is a floppy one with a conical skirt .
The other one is stiffer and has a cylindrical skirt which goes over in a conical skirt .
Which one belongs where?
Tx

[crazy steve]

http://www.xs11.com/forum/showthread.php?t=37209

[D0wn5h1ft]

Hey Don- What are the odds that the caliper o-ring can be re-used? I disassembled mine but did not pull the o-ring as I did not have re-build kits. Just cleaned them out. The pistons were a bugger to get back in.

I think your o-ring might have swollen a bit over time and this is why it's hard to get the piston back in.

Caliper Fiche

#11 would be what you might be having trouble with but I'm sure you already know that. My FZR600 had the same issue when I was changing brake pads a little while ago. The seals grabbed onto the piston and would not let go forcing me to manually have to "pump" them out with the brake lever...not fun.

[Ben Geutskens]

You look fast, cheap AND reliable to me.

[crazy steve]

The OEM seals are usually good to 80K miles as long as the system is clean; probably 99% of all brake problems can be attributed to corrosion/gunk in the system. If you find 'stuff' in one part, chances are extremely good it's everywhere else too.

My 'standard' service on any unknown brake system anymore is to fully disassemble it and clean everything. I have had to replace seals on occasion, but that's usually when the PO tried to make the dirty system work with corroded parts and the rough surfaces damaged the seals. Generally, the parts that need replacing are the caliper and master cylinder pistons as they'll get rusty.

Thoroughly cleaning the o-ring groove in the caliper is critical for operation.

[Ben Geutskens]

Yes, thanks, that's what I did.
Especially the grooves for the calipers O-rings, as in my case corrosion took place, which I meticulously removed with a copper snugly fitted scraper, cleaned and flushed.