How to rebuild your rear master cylinder


Step-by-step tutorials on how to maintain and fix your GL1100
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ZERGDOGG
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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Wed May 09, 2012 9:33 pm



All rebuilt and ready to go back on....
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WingAdmin
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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Thu May 10, 2012 11:22 am

Good job! It looks like new!

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wndoguy
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Re: How to rebuild your rear master cylinder

Post by wndoguy » Tue Jun 19, 2012 12:55 am

On the 2nd picture in this tutorial, there is a wire shown. This wire has come has torn during something I have done, but I can't find where the other end of the wire is. I can trace it to a connector just above the brake switch, but can find the end that goes to the left in this picture. Can you help me find the end of my wire please? LOL. I just rebuilt my master cyclinder, removed my rear wheel and shocks all with the help of these tutorials. Great job.
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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Tue Jun 19, 2012 9:38 am

wndoguy wrote:On the 2nd picture in this tutorial, there is a wire shown. This wire has come has torn during something I have done, but I can't find where the other end of the wire is. I can trace it to a connector just above the brake switch, but can find the end that goes to the left in this picture. Can you help me find the end of my wire please? LOL. I just rebuilt my master cyclinder, removed my rear wheel and shocks all with the help of these tutorials. Great job.
I don't remember what this wire is - if I were going to guess, I'd say it's for the rear air suspension pressure switch. What color is it? It's hard to tell through the grime in the picture.

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Re: How to rebuild your rear master cylinder

Post by wndoguy » Tue Jun 19, 2012 11:54 am

Ahhhh, you may have something there. The wire is green. And I installed new Progressive shocks on the back while things were apart, and removed the hoses etc for the old air shocks. I should check the hardware I took out and see if it would match up with anything on there. Good thought.
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Rick_MD
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Re: How to rebuild your rear master cylinder

Post by Rick_MD » Fri Jun 22, 2012 7:51 pm

Maybe I am missing something.

I went to Parts N More via the link in the post and tried to find a rear master cylinder r/b kit for my '82 GL1100I. No listing at all. I've tried searching a few times.

Suggestions?

My rear caliper locked up the other day on the way to work. Such excitement! :shock:

NOT!

I figured I would do them both and the lines at the same time. Don't want to repeat that skid. I jammed the pedal down and then lifted it up with my foot. It finally released a little. Then hit it again and absolutly nothing. No pressure on the pedal at all.

I rode her back home with just downshifting and the front brake. Such fun. :roll: :roll:

I got home and took a quick peek under the saddle bag to find that the brake hose had also broken off at the caliper. Smoked pads and rotor and a hose to boot. Looks like complete brake restoration in my near future. Unless someone in the near vicinity has some extra time and energy of which I have very little of either. :mrgreen:

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ZERGDOGG
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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Fri Jun 22, 2012 8:30 pm


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Rick_MD
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Re: How to rebuild your rear master cylinder

Post by Rick_MD » Sat Jun 23, 2012 7:50 pm

On closer inspection, I will be needing a rear brake caliper and rotor (in decent shape, please).

I turns out that the back brakes got so hot that it melted part of the caliper and damaged the rotor as well as broke the brake hose.

Anyone out there have one?

Thanks,

Rick

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Re: How to rebuild your rear master cylinder

Post by Rick_MD » Sat Jun 23, 2012 7:52 pm

Thank you. One is ordered and on the way.

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ZERGDOGG
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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Sat Jun 23, 2012 7:55 pm

your welcome and good luck with the build . I buy lots of bike parts on Ebay as the older parts are getting hard to find now , try Ebay for the used caliper and rotors I do see them there....cheers......

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Re: How to rebuild your rear master cylinder

Post by prc » Wed Jan 16, 2013 4:45 pm

Great How To, thanks
Doh! after all this time with the kit sitting around, I went to reassemble the master cylinder this morning only to find that the new (K&L rebuild kit #32-4271) piston has no rubber seal !?
prc

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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Wed Jan 16, 2013 5:20 pm

when I googled your kit I see this picture......is yours different?
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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Wed Jan 16, 2013 9:47 pm

prc wrote:Great How To, thanks
Doh! after all this time with the kit sitting around, I went to reassemble the master cylinder this morning only to find that the new (K&L rebuild kit #32-4271) piston has no rubber seal !?
prc
On the rebuild kits I have used, the piston comes with no seal installed. You have to lube up the piston and seal with some brake fluid, and gently stretch it to slip it over the piston into the slot. Make sure the seal is facing the right way around!

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Re: How to rebuild your rear master cylinder

Post by prc » Thu Jan 17, 2013 6:34 am

Yes, that looks to be the kit I have.
Ooops, I may have been thinking that the spring had a rubber seal on both ends and installed it as so.
Which is the proper orientation for the piston seal?
Thanks

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Re: How to rebuild your rear master cylinder

Post by prc » Thu Jan 17, 2013 3:15 pm

OK, I think I have the parts in the correct orientation, thanks for your help.
Tried to load a pic but cant for some reason.
When I click on "Add the file" it deletes the file selected, oh well.

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Re: How to rebuild your rear master cylinder

Post by warnett » Mon Mar 25, 2013 11:33 pm

I used carb cleaner to blow through the 2 holes and then blew them out with air. Help that didn't hurt anything.????

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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Tue Mar 26, 2013 6:39 am

warnett wrote:I used carb cleaner to blow through the 2 holes and then blew them out with air. Help that didn't hurt anything.????
That should be fine.

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Re: How to rebuild your rear master cylinder

Post by warnett » Tue Mar 26, 2013 9:56 am

wow can't believe I put help instead of hope. Thanks for reply

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Re: How to rebuild your rear master cylinder

Post by tony112668 » Fri Mar 29, 2013 5:22 pm

Ok after trying to rebuild my MC,my inner spring is tapered ONLY has the seal on the small end with the hole. your DIY shows that side pointing out of the cylinder,(towards circlip) the larger diameter spring end (on the other end) that is the side which your diagram shows to insert into the cylinder. IS there supposed to be a seal on each end?
the way it came apart was the small end of spring has the seal,and that end was inserted INTO the cylinder (with seal) but the other end was just an open ended spring.that had no seal.your diagram shows the small end facing OUT of the MC towards the Clip.. maybe the guy before me re-assembled it incorrectly???

if you took a picture of that whole spring assembly outside the MC BEFORE you inserted it back in,would have been a better help. your diagram here shows the end of the inner spring ALREADY INSERTED into the MC, so you cant see the end and if it has a seal...

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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Sun Mar 31, 2013 4:32 pm

tony112668 wrote:Ok after trying to rebuild my MC,my inner spring is tapered ONLY has the seal on the small end with the hole. your DIY shows that side pointing out of the cylinder,(towards circlip) the larger diameter spring end (on the other end) that is the side which your diagram shows to insert into the cylinder. IS there supposed to be a seal on each end?
the way it came apart was the small end of spring has the seal,and that end was inserted INTO the cylinder (with seal) but the other end was just an open ended spring.that had no seal.your diagram shows the small end facing OUT of the MC towards the Clip.. maybe the guy before me re-assembled it incorrectly???

if you took a picture of that whole spring assembly outside the MC BEFORE you inserted it back in,would have been a better help. your diagram here shows the end of the inner spring ALREADY INSERTED into the MC, so you cant see the end and if it has a seal...
The way yours was assembled had the spring in backward. The large end of the spring goes down into the master cylinder, there is nothing else that goes in there other than the bare spring end. The small end of the spring has the metal cap and the rubber top that fits into the metal cap as shown in the picture.

Image

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Re: How to rebuild your rear master cylinder

Post by tony112668 » Tue Apr 02, 2013 4:26 pm

WingAdmin wrote:
tony112668 wrote:Ok after trying to rebuild my MC,my inner spring is tapered ONLY has the seal on the small end with the hole. your DIY shows that side pointing out of the cylinder,(towards circlip) the larger diameter spring end (on the other end) that is the side which your diagram shows to insert into the cylinder. IS there supposed to be a seal on each end?
the way it came apart was the small end of spring has the seal,and that end was inserted INTO the cylinder (with seal) but the other end was just an open ended spring.that had no seal.your diagram shows the small end facing OUT of the MC towards the Clip.. maybe the guy before me re-assembled it incorrectly???

if you took a picture of that whole spring assembly outside the MC BEFORE you inserted it back in,would have been a better help. your diagram here shows the end of the inner spring ALREADY INSERTED into the MC, so you cant see the end and if it has a seal...
The way yours was assembled had the spring in backward. The large end of the spring goes down into the master cylinder, there is nothing else that goes in there other than the bare spring end. The small end of the spring has the metal cap and the rubber top that fits into the metal cap as shown in the picture.
ok so "bare large end of tapered spring" goes in first and the seal faces the piston. THANK YOU SO MUCH !!! yeah I had a feeling it was wrong - much appreciated!

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Re: How to rebuild your rear master cylinder

Post by GW-Newbie2013 » Wed Aug 14, 2013 1:42 am

On my rear master, I am unable to get it out from the seat because of a smaller line which I am assuming is the line that goes to one of the calipers. I'm just unable to unbolt it from the cylinder. It sits right behind the resevoir line. Any thoughts on how to break it and get it off there? by breaking I mean loosening it so I can unscrew it and free the master cylinder for the rebuild.
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Re: How to rebuild your rear master cylinder

Post by warnett » Wed Aug 14, 2013 7:01 am

From where you say it is sounds like thats the clutch master cyl. Brake on the other side down low.

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Re: How to rebuild your rear master cylinder

Post by jellyfishmoonpie » Sat Aug 24, 2013 12:12 am

I just did this on my gl1000.i find the easiest method to push out stuck pistons (master cylinder or caliper pistons) is to actually pump them out via another master cylinder. Like I hooked up my from the master cylinder to the rear master cylinder and pumped the rear piston out, took very little effort, and it had sat and rusted for 6 years!

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Re: How to rebuild your rear master cylinder

Post by gexxie » Mon Jul 21, 2014 7:17 am

WingAdmin wrote:The expansion of the brake fluid is more due to the heat generated by the brakes than by the exhaust. Brakes perform one function: to turn kinetic energy (bike moving forward) into heat. Ever touch your brake rotors or calipers after a hard stop? (don't) They will be extremely hot - they can be hundreds of degrees. Watch the brake rotors of racing cars, and you'll see them glowing orange and white from heat.

This heat goes into the brake caliper, heating up the reservoir of brake fluid that is sitting behind the pistons and inside the caliper itself. This fluid expands and pushes back up into the master cylinder - so if that return port is plugged, it has nowhere to go. The end result: it does the only thing it can do, it pushes the pistons outwards, which engages (i.e. locks) your brakes.

I have a feeling the brake proportioning valve prevents pressure backing up from one caliper from affecting the other - so that brake runout (causing pulsing) on the rear brake, for instance, won't also cause the front brake to needlessly pulse on and off.
Hi, I joined this site today and already I think I have my answer. I just rasied a question (viewtopic.php?f=16&t=23080) but this thread gives me the next step. If my brake is siezing even without me using the brake, it has to be the heating of the fluid with no chance to return through the master cylinder. I've changed everything else!. So, need to buy some more bits and plan my weekend to get this finally fixed. Admin - this is just the best site ever.... Thanks



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