How to rebuild your rear master cylinder


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Willis333
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Re: How to rebuild your rear master cylinder

Post by Willis333 » Thu Apr 14, 2011 9:34 am



I obsessively cleaned my rear mc to where it looked almost new- considering the age. I used compressed air to work the plunger out- with pb blaster also of course. Someone else mentioning finding the correct grease filling and pumping grease/pressure into the mc to work the plunger out. I feel this is a great option seeing that the grease will lubricate as it pushes- it works WONDERFULLY with a brake caliper + getting seized pistons out. Cheers. Willis- Asheville, NC



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aawscotch
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Re: How to rebuild your rear master cylinder

Post by aawscotch » Fri Apr 29, 2011 1:03 pm

I just rebuilt the rear master cylinder on a 84' gl1200 that had been setting for nearly 10 years.After 2 days of soaking, I still couldn't blow the piston out with air.
I went to the parts store and got 2( my MC has 2 discharge lines) tubing nuts with the intention of brazing grease fittings into them.
I discovered that I could tap the inside of the tubing nuts with a 6mm by 1.0 thread right into them.So,I bought grease fittings with 6mm threads.
piston,spring and cup pushed right out with my grease gun.
Note: Will work with a 3/16 tubing nut if you can't find the metric ones.

aawscotch
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aawscotch
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Re: How to rebuild your rear master cylinder

Post by aawscotch » Fri Apr 29, 2011 1:13 pm

I just joined and updated my profile so if any of you have a question or if I didn't explain my how to good enough, my email is on my profile
aawscotch

isthismuchbetter???
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Re: How to rebuild your rear master cylinder

Post by isthismuchbetter??? » Thu Oct 27, 2011 11:37 pm

Ok, I just looked at this great rebuild article again. I noticed this time that the one you are doing has a banjo fitting, where mine has a flared fitting. It also looks like the banjo fitting connects to a black HOSE, where mine has a flared fitting using steel tubing. I believe my steel tubing goes to the front brake, as mine, a 1983 GL1100A Aspencade has the dual brake system. The rear master cylinder I got on ebay requires the banjo fitting, so I can't use it. And the ebay one seems to only have one outlet. Is 1983 the first use of the dual brake system? I have not yet crawled around out in the cold to see if my rear master cylinder has 2 outlets, one for front and one for back brakes. What is a good manual and what is a good source for one? I have been told to trash the CLYMER one I just bought.

I don't get back to this forum enough, so please also send a reply to me at rocketmn@nemontel.net

Thanks!

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WingAdmin
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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Fri Oct 28, 2011 1:35 pm

isthismuchbetter??? wrote:Ok, I just looked at this great rebuild article again. I noticed this time that the one you are doing has a banjo fitting, where mine has a flared fitting. It also looks like the banjo fitting connects to a black HOSE, where mine has a flared fitting using steel tubing. I believe my steel tubing goes to the front brake, as mine, a 1983 GL1100A Aspencade has the dual brake system. The rear master cylinder I got on ebay requires the banjo fitting, so I can't use it. And the ebay one seems to only have one outlet. Is 1983 the first use of the dual brake system? I have not yet crawled around out in the cold to see if my rear master cylinder has 2 outlets, one for front and one for back brakes. What is a good manual and what is a good source for one? I have been told to trash the CLYMER one I just bought.

I don't get back to this forum enough, so please also send a reply to me at rocketmn@nemontel.net

Thanks!
The Clymer really isn't the greatest - for completeness and correctness, I'd recommend the original Honda service manual.

The 83 was the first to use the linked brakes. The rear master cylinder has a single outlet, which then goes to a splitter, which then goes to the rear caliper and one of the front calipers.

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Re: How to rebuild your rear master cylinder

Post by isthismuchbetter??? » Fri Oct 28, 2011 1:55 pm

Hi, thanks. yeah, i have finally been getting enough input from this and another forum to understand more of what i have, the splitter,lower pressure, etc and I have just sent an email via ebay, so it is recorded, telling the seller about all of this, and that it is as useless for my 83, the one I bought being from and 82, as a dish of ice cream in the summer with no dish, and have formally requested a full refund. Hope the guy is co-operative. Even he has had no luck in finding a solution, yet he says he has found none while feeling there was some sort of fitting that would work, as he says he has sold these before and they have been used. Well, maybe some have, and being used to 2 seperate brake systems, maybe they didn't mind some lesser pressure at the rear brake as long as the seperate front was still at max. When i first got a bike i was told not to use too much rear brake as it would lock and skid, and practice more use of front brake. How many decades ago was I on that near new 71 Honda 450? yeeks, I don't want to know!!!!

timwingard
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Re: How to rebuild your rear master cylinder

Post by timwingard » Mon Mar 05, 2012 10:27 am

I have a problem where the rebuilt master cyclinder lubricated with clean brake fluid is not smoothly returning back up when depressed. It sticks down most times, but occassionaly comes back up. I removed it and reassembled and I'm getting the same issue. What might be the problem is when you receive the rebuild kit you have to put a piece of rubber on the cyclinder before installing. Could I have installed this piece of rubber upside down? Any instructions on that piece of the installation? How do you know what side goes up on the piece of rubber?

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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Mon Mar 05, 2012 10:37 am

timwingard wrote:I have a problem where the rebuilt master cyclinder lubricated with clean brake fluid is not smoothly returning back up when depressed. It sticks down most times, but occassionaly comes back up. I removed it and reassembled and I'm getting the same issue. What might be the problem is when you receive the rebuild kit you have to put a piece of rubber on the cyclinder before installing. Could I have installed this piece of rubber upside down? Any instructions on that piece of the installation? How do you know what side goes up on the piece of rubber?
Yes, if you look closely, that piece of rubber is not cylindrical, it's wider on one side than it is on the other. If you look closely, you can see the direction it should go, with the smaller diameter end closer to the end of the shaft as shown:

Image

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Re: How to rebuild your rear master cylinder

Post by timwingard » Tue Mar 06, 2012 7:16 pm

Thanks for the clarification on the direction of the rubber piece. I ended up taking it back off the bike this evening, cleaing the old pieces and putting them back in. Ahh, suddenly it works correctly. The rebuild kit pieces are slightly, larger. Large enough to cause severe binding but not so large as to prevent me from putting the Master cyclinder back together. But I had a leak when I reinstalled but it could have been that I didn't tighten the brake line all the way. But since it got dark, I had to quite. I won't know until tomorrow if the leak is real, or Tim made. Have you ever heard of these rebuild kits not being the right size? I will have to investigate where I bought it.

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ZERGDOGG
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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Tue Mar 13, 2012 11:12 am

just bought the rebuild kit as my rear wheel is locked up on my 84 GL1200 standard...but my kit has an extra rubber boot any idea what that is for?
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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Wed Mar 14, 2012 10:53 am

Not sure what extra rubber boot you're talking about - the cap, perhaps?

Here:

Brake kit parts description
Brake kit parts description


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ZERGDOGG
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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Wed Mar 14, 2012 1:12 pm

yes I mean the "goes on top when all its all assembled. Piston pokes out through the hole" part I don't see that part in your assembly procedure it doesn't look big enough to replace the MC boot you show in the pictures though I haven't measured it yet...

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ZERGDOGG
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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Wed Mar 14, 2012 5:22 pm

Ok , I just took another look at the bike it has the smaller cap on it not the big boot that you show in the pictures , does that mean that the MC has been rebuilt before? I only have 24,000 miles on the bike and bought it a few years ago with 20,000 on it..I assume if I'm tearing apart the MC to clean the return port I should replace the parts anyway?....cheers

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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Wed Mar 14, 2012 9:24 pm

ZERGDOGG wrote:Ok , I just took another look at the bike it has the smaller cap on it not the big boot that you show in the pictures , does that mean that the MC has been rebuilt before? I only have 24,000 miles on the bike and bought it a few years ago with 20,000 on it..I assume if I'm tearing apart the MC to clean the return port I should replace the parts anyway?....cheers
The GL1200 parts diagram I have shows a boot that looks the same as the GL1100. Someone more familiar with the GL1200 will have to speak to whether it is the same or not.

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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Thu Mar 15, 2012 9:48 pm

started to take the MC off and after I drained the fluid I decided to recheck the rear caliper but it was still locked up even after I loosed up the zerk fitting and the took off the fluid line . the caliper still wont budge off the rotor. so... wd40 and large pliers to relieve some of the pressure on the pads... I eventually got it off yaah...probably have to put the fluid back in the system to be able to get the pistons out ..I bought the rebuild kit for the calipers and some kevlar carbon pads so looking forward to more face time with the bike and your awesome instructions

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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Fri Mar 16, 2012 11:29 am

ZERGDOGG wrote:started to take the MC off and after I drained the fluid I decided to recheck the rear caliper but it was still locked up even after I loosed up the zerk fitting and the took off the fluid line . the caliper still wont budge off the rotor. so... wd40 and large pliers to relieve some of the pressure on the pads... I eventually got it off yaah...probably have to put the fluid back in the system to be able to get the pistons out ..I bought the rebuild kit for the calipers and some kevlar carbon pads so looking forward to more face time with the bike and your awesome instructions
Careful that your pads are not too hard. Bike pads are typically very soft, and the rotors are very hard, so that the pads wear and the rotors (mostly) don't. Pads are cheap to replace, rotors are very expensive.

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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Sat Mar 17, 2012 12:27 am

good advise as the rotors are not very thick to start with!.this is what I found out...
Carbon-Kevlar pads, often referred to as organic pads, usually have a small percentage of iron or nonferrous metal and are softer than other friction materials. Carbon-Kevlar pads typically run clean and quiet, and offer good stopping power. They have an extremely long service life and are not abrasive to the rotor because they generate less heat than other friction materials.

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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Mon Mar 19, 2012 12:27 pm

ZERGDOGG wrote:They have an extremely long service life and are not abrasive to the rotor because they generate less heat than other friction materials.
I'm sorry, but this sounds like marketing BS to me.

They generate less heat than other friction materials? The job of a braking system is to turn kinetic energy (motion of the bike) into heat energy. They do this through friction. The amount of heat that is generated is not a variable - either the braking system is stopping the bike and turning the kinetic energy into heat energy, or it's not. If you have a 1000 lb bike that is going 30 mph, and you brake it to a stop, the amount of heat created by the brakes is identical regardless of the pads in use.

And since whendoes abrasiveness have anything to do with heat generation?

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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Mon Mar 19, 2012 3:20 pm

dont really know much about the pads , I did a google search for good pads and came across these.. I'll keep an eye on the rotor and if they start scoring I'll rip them off and look for something else. Ive done brake jobs on my cars but this the first bike job for me. I never worried about car pads scoring the rotor as they are cheap enough to replace but a 30 year old bike with limited parts sourcing is a different thing all together...

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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Sat Mar 24, 2012 8:15 pm

what they look like after using the grease gun to getthe pistons out and after I cleaned the grease off but not sanding yet, I saw a youtube post where a guy used crumpled tin foil instead of sand paper to clean the crud off....
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ZERGDOGG
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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Tue Apr 03, 2012 8:47 am

where I've gotten so to far ( not perfect but hopefully good enough), rubber seals next and then on to the Master Cyl rebuild.....
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Re: How to rebuild your rear master cylinder

Post by WingAdmin » Tue Apr 03, 2012 2:02 pm

Wow, great job! Looks like new!

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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Tue Apr 03, 2012 2:43 pm

thanks, I just did a last minute brake cleaner spray and I found out its a bad idea to spray brake cleaner on duplicolor caliper paint as it washed off even after it dried for 24 hours!

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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Tue May 08, 2012 6:45 pm

finally got to the Gl1200 MC rebuild , I got it apart and I'm in the cleanup phase. couldn't get the nut off without a flarenut wrench don't try it with an open end wrench it will round off the soft metal nut. had some problem with the cclip as it well is much deeper than the 1100 bike MC that you show.had to use a pick to force it out.using a punch in the end I stood on it and pulled straight up to get it out without any problems.just blew in the holes and the spring came out easily.I destroyed the rubber boot trying to get it off the wire reinforcement on the larger end of the boot had rusted up and fused to the wall of the MC. in the 1200 you dont need to remove the end of the rod to get the boot off or back on.note the small hole that was party clogged up but clean up for the photo, more cleaning to go......
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Re: How to rebuild your rear master cylinder

Post by ZERGDOGG » Wed May 09, 2012 1:44 am

sorry I wish I could edit a post to correct errors.....the statement "in the 1200 you dont need to remove the end of the rod to get the boot off or back on" is not correct I definitely had to remove the clevis to get the new boot on ,be sure to lubricate rubber and any metal part you need to slide over with lots of brake fluid ,even then it was pretty fiddly getting the boot to seat right....thanks again for the orig post which inspired me to do this job myself...bleeding the lines next..............cheers



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