How to rebuild your rear master cylinder


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bobbybiscuit
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Re: How to rebuild your rear master cylinder

Post by bobbybiscuit » Sun Sep 04, 2016 6:35 am



Checked brake line to caliper - not blocked. Took rest to pieces and the the piston is seized inside master cylinder. It was only 18 months ago that the garage put in a new kit in the master cylinder. Got to try and get out the piston out of the master cylinder. Its so tight. not happy after getting so close to getting bike on the road after 14 months. :-(



PRACTIKALGUY
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Re: How to rebuild your rear master cylinder

Post by PRACTIKALGUY » Tue Oct 11, 2016 3:37 pm

Is it the same procedure for an '83 Aspencade?
Also, all the '83 SS brake line kits have a rear line and two front lines which appear to be the same length. I assume that there's hard line from the rear M/C up to a point forward?

dwight007fchr
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Re: How to rebuild your rear master cylinder

Post by dwight007fchr » Mon Nov 07, 2016 9:31 pm

Wilcoyj & Boby Biscuite.......I have an 83 Gl1100 Interstate and have been rebuilding the calipers and master brake cyliner, and I ran into the same frustrating problem that you posted. With fresh rebuild on the rear brakes, and a fresh rear master cylinder rebuild, I am having a terrible time getting any brake fluid down to the bleeder screw on the rear caliper. I was using a hand vac. and was not getting any fluid to draw thru as they show on numerous Youtube videos. I have been going crazy wondering what in the world was the problem. I eventually got a very small amount to the rear brakes over several days of pumping/bleeding, and finally got the rear calipers to close up onto the disc. But since one side of the front brake works off the rear master cylinder, I still have no brakes since the front one is off (I am trying to use the brake fluid to push off the brake pistons so I can rebuild the front one). So, I am not getting any brake fluid to the front even after the rear pistons are firmly closed on the brake pads/caliper. The hand vacuum does nothing. So now I am thinking that the brake line might be clogged as was the case with you.

Isnt there also a "Tee" connection in the brake line that has a pressure valve in it? Guess I just need to pop it open and use compressed air into the line to unclog it.

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Wilcoy02
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98 valkyrie sold 8/16

Re: How to rebuild your rear master cylinder

Post by Wilcoy02 » Mon Nov 07, 2016 9:51 pm

Do not know if there is a tee or not. I used brake cleaner into the line and blew it thru the lines with compressed air. Took several tries but I finally got a black glob out of the line. I went from master to caliper then switched and went from caliper to master. Then I did the same to the front caliper.

Good luck you'll get it.

dwight007fchr
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Re: How to rebuild your rear master cylinder

Post by dwight007fchr » Mon Nov 07, 2016 10:44 pm

Wilcoy......Thanks.......I will give try the compressed air tomorrow and see if that does the trick. I would have never thought that the lines might be clogged if I had not seen these posts.....this site is a big help for sure.

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Wilcoy02
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98 valkyrie sold 8/16

Re: How to rebuild your rear master cylinder

Post by Wilcoy02 » Tue Nov 08, 2016 12:09 am

make sure you have plenty of rags around every thing. Don't want the brake fluid to get on any paint.

dwight007fchr
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Re: How to rebuild your rear master cylinder

Post by dwight007fchr » Tue Nov 08, 2016 6:46 am

Wilcoy......Rags....thats a big 10-4 from my backdoor.

As Trump will Make America Great Again,
We will make our old Wings Great Again.

bobbybiscuit
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Re: How to rebuild your rear master cylinder

Post by bobbybiscuit » Tue Nov 08, 2016 7:17 am

My problem was the rear master cylinder - although the connecting arm was going in and out, it was not actually pushing the piston down the bore. So no brake fluid was going through. I actually replaced the rear master cylinder from one advertised on ebay as working - popped that one in and hey presto it worked - brakes bled very easily to be honest.

Went out last Saturday on my goldwing (as I just got it back on the road after 15 months) and rode 100 miles as a tester - during next week hoping to get out for a longer 250 mile round trip.

If you are comparing Trump to Goldwings then it could be the end for Goldwings :-) lol. I would hate to be living the the USA at the moment - not a good choice of candidates but I think better the devil you know! :lol:

dwight007fchr
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Re: How to rebuild your rear master cylinder

Post by dwight007fchr » Tue Nov 08, 2016 7:52 am

bobby biscuit......Yep, my first try on the rear master cylinder I did not replace the rubber seals since they looked fine. I think I goofed when I put some 10w30 oil on the rubber seals thinking some oil would be good for them. I think that caused them to swell up some and when I put it back on, the internal spring would not push back the piston with seal very good. So I had to get a rebuild kit, and the guy told me to ONLY use the enclosed red vegetable based grease and never oil. Got that on, and it pumps back and forth fine....but not pumping much brake fluid. So, Im hoping its just the line partially clogged up.

Good to see you are putting some miles on your bike......as soon as I get these brakes working, I can give this naked wing a good try. I got the engine running super fine, and cant wait to see how she compares to my fully dressed wing.

Trump.....well, I will admit that I fully support him and his views. Just hope the polls are not rigged enough to cause that sick corrupt evil Killery to move into the white house.

Roadtrekker
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Re: How to rebuild your rear master cylinder

Post by Roadtrekker » Wed Feb 01, 2017 4:37 pm

Love the forum and find it invaluable rebuilding my 81 Goldwing GL1100I. I ran into a problem after rebuild of rear master cyl. I had it all together, filled the reservoir to fill the cyl and flush some fresh fluid through the line. The pedal worked fine, reservoir went down about half way, no fluid ever came out the line that isn't connected to the caliper. Brake travel suddenly stopped and will not hardly move. I figured I'd give a shout out before I take it all apart again. I'm sure I put the seals, piston, etc in correctly. Any ideas? Thanks again !!! This is a great forum for the DIY folks.

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Phunnybone
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Re: How to rebuild your rear master cylinder

Post by Phunnybone » Sat Dec 02, 2017 8:18 am

MJSantos wrote:
Sun Jun 20, 2010 11:36 am
Another interesting symptom dealing with the master cylinder that I ran into was the small hole being partially plugged. With the bike sitting there idling the rear brake would lockup without even touching the pedal. Since it's a linked system you would think that this would affect the front but it didn't. After the bike cooled down everything was fine. I rebuilt the rear caliper but still had the same problem. Did the master found the small hole problem, everything is fine now. Shows how much expansion there is with brake fluid at the back wheel due to the close proximity of the exhaust.
My front brake did the sam thing even after rebuilding the master cylinder and caliper. Replacing the brake hose with an HEL line fixed the issue. A post on another site indicated that the interior of the old hose might be collapsing and causing the problem.



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