Rear master cylinder problems

[unicorncomputer]

on my 79 1100 special my rear brakes were frozen. I was changing the tire anyway so I decided to remove and clean out the master cylinder. After putting it all back together, it doesn't seem to pump fluid at all. I did not take apart the plunger on the bottom. I am guessing that this is where my problem is. Does anybody have any pictorals on this and am I probably correct in that the plunger is where the problem is?

Thanks in advance,

Steve

[unicorncomputer]

Is there a way to test the master cylinder?

[MPittma100]

Rear brakes

You would be doing yourself a favor by rebuilding the master cylinder using a new kit. Also a good idea to rebuild the caliper especially if it has been a while. When you do, replace the caliper piston if pitted.

Check your date on the brake line as it may be too old.

It is best to bleed the brakes on these bikes with a vacuum gun bleeder. Pumping the lever is not often effective.

[unicorncomputer]

The system now has no fluid in it. Could it be fine and just not pumping fluid through with out a vacuum gun?

I don't have such a tool, is there another way to accomplish it?

Thank you for your knowledge.

[DiverRay]

You need to "bench bleed" the master before you put it back on the bike.
With the master in a vise, and fluid in it, hold a finger over the hole the brake line bolts to. Push on the master with a screw driver or bolt or something to compress it, move your finger off the hole, then put it back on. Repeat until you have fluid coming out, the re-install on the bike, hook up the hose, and try bleeding again.

[Rasputin]

I do a different version of DiverRay's method, but on the bike. I simply remove the brake hose at the caliper end and use my fingers to seal it off there, while doing the push part with the brake pedal. It works for me.

[SFerinTEXAS]

Could it be fine and just not pumping fluid through with out a vacuum gun?

You are getting great advice on bleeding. The answer to your question is NO.

Gonna have to take it apart and clean it, caliper too. The only way. May not need any parts.

[Fearthepack]

Don't forget the Spooge Hole in the master cylinder.

[unicorncomputer]

You would be doing yourself a favor by rebuilding the master cylinder using a new kit. Also a good idea to rebuild the caliper especially if it has been a while. When you do, replace the caliper piston if pitted.

Check your date on the brake line as it may be too old.

It is best to bleed the brakes on these bikes with a vacuum gun bleeder. Pumping the lever is not often effective.

Is there a pictorial anywhere on how to rebuild the rear master cylinder?

Just pulled the bike out and need to get this done.

Thank you in advance,

Steve

[JeffH]

Been looking for a tutorial. Here are a few things i found:

Some discussion about brake bleeding
http://www.xs11.com/forum/showthread...+master&page=2

Few pics of Front Master repairs
http://www.xs11.com/forum/showthread.php?t=37209

Few pics of Rear Master repairs
http://www.xs11.com/forum/showthread.php?t=14

Not much help but maybe its a start. As stated, rear can be a bit tricky to get pressure.
As Ray said, with mine I did Bench Sync to get it primed, then needed Mighty Vac to get ALL the air pockets
out of the nooks & crannies in that rear brake system.

Jeff

[unicorncomputer]

Thank you, I did find these too.

But since I have never rebuilt a master cylinder, I don't really know what I am in for.

[JeffH]

Its not complicated at all. Do you have an XS1100 manual?

If you look in CatatonicBug signature I think you can still download a manual there.

As Mike said, do the caliper too and check condition of piston for excessive rust + condition of that rear brake line if its original rubber it should be replaced just to be safe.

Jeff

[unicorncomputer]

I got it apart. The bottom rubber piece came off before I could see what direction it goes in. I have pics here that I think are the right direction. Can someone confirm this?

And how the hell do you get the one in middle over the big piece at the bottom?

http://s1334.photobucket.com/user/un...1100%20Special

[kboehringer]

Bring the one in the middle down from the top not up from the bottom. It's new and quite pliable but I usually use a TINY bit of o-ring grease on it so it will slide over the humps easily (a LITTLE of any grease will do).

You have it assembled correctly in pic #2.

KURT

[unicorncomputer]

Thank you all. It is back together and working again.

Now to clean the carbs and get the beast fired up and breathing again so I can get it sold.