How to rebuild your front master cylinder


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How to rebuild your front master cylinder

Postby WingAdmin » Sun Mar 15, 2009 10:26 pm



I used a front master cylinder rebuild kit from Partsnmore.com for my 1982 GL1100A Aspencade.

1. Place protective cloths underneath the master cylinder - brake fluid will eat the paint off your bike, and if it drips onto the ABS plastic of your fairing, it will cause the plastic to crack and disintegrate. I can't emphasize this enough!

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2. Undo the brake line fitting banjo bolt. Be ready to catch dripping brake fluid.

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3. Disconnect the brake switch wires.

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4. Remove the two bolts holding the master cylinder to the handlebar.

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5. Remove the master cylinder from the handlebar and to a tube that will catch the brake fluid that will be coming out of it.

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6. Remove the locknut on the bottom of the brake lever assembly.

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7. Remove the brake lever pivot pin.

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8. Remove the reservoir cap, and empty the reservoir. Clean both liberally with brake cleaner.

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8a. Now is a good time to clean the brake fluid return port in the master cylinder. It is a tiny pinhole inside a small depression - and if it gets clogged (as it will, with sludge and debris), your front brakes will drag or lock solid when they heat up. I use a small piece of stiff wire clipped from a wire brush, held with needlenose pliers to clean this out.

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Note: Some reservoirs have a plastic cover with two small holes in it covering both the supply and return ports for the master cylinder. This plastic cover is part of the actual reservoir. If this is the case (you'll know because instead of seeing metal like you see in the picture above, you'll see plastic), you will need to remove the plastic reservoir from the master cylinder in order to clear the ports. The reservoir twists/pulls off, and is held in place with an O-ring. It normally takes a fair amount of force and effort to remove the reservoir. It simply pushes back on once it has been removed.

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9. Remove the rubber cap from the piston end.

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10. Looking into the piston area, you will see the circlip holding the piston assembly in place.

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11. Depress the piston with your finger to relieve the tension, then use snap ring pliers to compress the circlip. Once it is compressed, relieve the piston and allow it to push the circlip out of the master cylinder.

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12. Remove the piston from the master cylinder.

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13. Inside you will see the second rubber cap. Using a small screwdriver, push the cap to one side, then pull it out.

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14. Remove the spring. Clean the circlip channel inside the master cylinder of any corrosion and debris, and clean the master cylinder liberally with brake cleaner.

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15. On the new spring, you will see one end that has a metal disk attached, with a hole in one end.

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16. Lubricate the new rubber cap with clean brake fluid, and place it over the disk on the end of the spring.

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17. Gently push the spring and the rubber cap into the master cylinder.

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18. Lubricate the rubber seal on the new piston with clean brake fluid, and gently insert it into the master cylinder.

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19. Place the new circlip on the piston, grab the circlip with your snap ring pliers, and push the piston into the master cylinder.

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20. When the circlip reaches the channel, release the snap ring pliers and allow it to snap into the channel. Release pressure on the piston.

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21. Lubricate the new rubber boot with clean brake fluid and insert it over the piston.

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22. Ensure the base of the boot is pushed securely into the channel around the piston, and that the top of the boot seats correctly into the channel on the top of the piston.

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23. Lubricate the brake lever pivot pin, and insert it through the frame and brake lever. Screw it into place.

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24. Apply and tighten the brake lever lock nut.

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25. Assemble the master cylinder back onto the handlebar and tighten it in place, making sure the angle of the brake lever is correct before tightening.

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26. Reattach the brake light switch connectors.

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27. Attach the brake line banjo bolt with new crush washers.

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28. Fill the reservoir, bleed the brakes, and check for leaks before fitting the rubber brake line boot over the fitting.

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Re: How to rebuild your front master cylinder

Postby tumunga » Sat Apr 03, 2010 4:32 am

Just thanking you for the instructions again sir.
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Re: How to rebuild your front master cylinder

Postby Jdept » Fri Oct 29, 2010 3:00 pm

I was wondering if anyone knows of a suitable replacement that would work for a '82 GL1100I front master cylinder/reservoir. The main reason why I ask is my reservoir looks like it's about to disintegrate and I believe both of my screw posts may be no go (bought it zip tied). I really don't want to pay the price for a plastic replacement when I see other front master cylinders that are metal and usually available chromed for the same price. Would a confirmable front master cylinder that's used on a dual-caliper/dual-piston with independent brakes work for me? Anybody have any ideas Harley? Triumph? Kawasaki? Any special years to look out for? I have seen a lot of good looking masters for sale on ebay that are well under $40 and that's what I am looking for without having to a rebuild of the master.

~J :?: :ugeek:
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Re: How to rebuild your front master cylinder

Postby WingAdmin » Fri Oct 29, 2010 3:34 pm

I know the plastic reservoirs are available fairly cheap at PartsnMore. I also know of someone who bought one of those chrome master cylinder replacements (with built in reservoir) from eBay and was quite happy with it.
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Re: How to rebuild your front master cylinder

Postby theoj » Mon Nov 01, 2010 10:30 am

@Jdept: those from the Honda cx500custom will fit also!
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Re: How to rebuild your front master cylinder

Postby macka » Tue May 31, 2011 6:40 am

Why do you use ATF to lubricate the rubber bits?
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Re: How to rebuild your front master cylinder

Postby WingAdmin » Tue May 31, 2011 2:20 pm

macka wrote:Why do you use ATF to lubricate the rubber bits?


Because as hydraulic fluid it's compatible (in small quantities) with brake fluid, it lubricates well, and doesn't hygroscopically suck moisture out of the air like brake fluid does. That way you can lubricate the things going together to avoid damaging the seals without introducing moisture into the system.
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Re: How to rebuild your front master cylinder

Postby dwsinclair » Wed Jun 01, 2011 11:49 am

Couple of quick tips on this job:

1.) I have been using the master replacement from the EBay guy in Florida (he has both chrome and non) for two seasons and it works perfectly - no better/no worse than the original. I felt all new was a better choice for me. Stock lines work.
2.) The "A /number 1" best trick for bleeding front brakes is to remove one of the caliper bolts and tilt the caliper so that the bleeder screw is as on top as you can get it. Obviously, make sure a good bit of the pads are still on the disc. There's a bubble that hides above the screw that really likes to drive ya crazy. The result is a really perfect front feel.
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Re: How to rebuild your front master cylinder

Postby nickinf » Fri Jun 17, 2011 3:25 pm

I am trying to insert the rubber cap onto the spring and it will not fit into the channel how do i do this
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Re: How to rebuild your front master cylinder

Postby WingAdmin » Fri Jun 17, 2011 4:42 pm

nickinf wrote:I am trying to insert the rubber cap onto the spring and it will not fit into the channel how do i do this


I put the rubber cap upside down on my finger, then put the spring on top of it, holding it in place with my other two fingers. I then took the master cylinder and lowered it down onto the spring, until the cap was at the entrance to the cylinder - a gentle push, and it moved into the cylinder.
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Re: How to rebuild your front master cylinder

Postby MedicMike » Sat Sep 24, 2011 2:09 pm

Thanks for this article. I found out today I need to rebuild mine as well. I rebuilt the fron caliper this morning and then I could bleed the brake line, even with a Mity-Vac. I check the master cylinder and realized that the piston was sticking. Of course, I have to order the parts and the bike will sit for another few days. Any idea of any place online that sells a rebuild kit for an 83 Interstate. Parts N More has one for the 81-82 listed but nothing for the 83. Thanks.

This sucks. I registered it in June and haven't riden more that 20 miles total this summer.
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Re: How to rebuild your front master cylinder

Postby timwingard » Sun Nov 13, 2011 12:56 am

Hi, thanks for the directions and pictures. I am having a problem trying to remove the o-ring. The problem is that all three compression ring removers that I have purchased for this one job will not allow me full access into the cylinder to access the ring. I have tried trimming the metal off of one the compression ring removal tools to gain better acccess but I still haven't gotten it out. I have the master cylinder in a vice, I have tried pushing down on the cylinder and it is very hard to do at the same time I am trying to get the compression ring remover down in the slot where I can hardly see. I have spent hours trying all sort of variations of the three tools to no avail. Any suggestions, I am at a stand still. If I could I would just break the compression ring, but I can't even do that.
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Re: How to rebuild your front master cylinder

Postby timwingard » Sun Nov 13, 2011 8:40 am

Clarification - when I say compression ring, I really mean snap ring.
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Re: How to rebuild your front master cylinder

Postby WingAdmin » Sun Nov 13, 2011 11:32 am

I used a very small set of snap ring pliers and it popped right out with those. Notice I used straight pliers, not the right-angle pliers:

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That said, you could probably use a small pick device to grab one of the ends, pull it out, and then "convince" it to come the rest of the way out with a small flat blade screwdriver.

You might want to try fitting a C-clamp on it to apply pressure to the piston, retracting it and relieving the pressure from the snap ring to try to make it easier to remove.
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Re: How to rebuild your front master cylinder

Postby timwingard » Tue Nov 22, 2011 6:50 pm

I was having lots of trouble getting the snap ring out. The combination pliers were not working for me at all, where you change the heads. I tried three differnt brands, but the tips were not long enough and the base too fat for me to reach down in that cylinder. Finally I bought a single size inner ring remover set off the internet from Nothern Tool, but when I got them the points were too fat. I had to grind them down to fit the new snap ring. It was still a bear trying to grab that ring because the pliers were on the verge of being too fat. By pushing and wedging the piece I was trying to remove down to its lowest point, allowed me just enough room to finally grab and remove the ring. I suggest getting a small set of inner snap ring pliers with a long slim tip to attempt this. Not the versatile, change the tip variety. Possibly try Sears, because the autoparts stores in my area nor Home Depot had the kind I needed. I bought what they had, but they didn't work. Now I can continue my rebuild. Yea! Thanks WingAdmin for your advice and encouragement.
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Re: How to rebuild your front master cylinder

Postby dawgout81 » Mon Feb 13, 2012 7:30 pm

Last weekend I got all my brake cylinders rebuilt, including the master.

However, after putting the master cylinder aside on the work table after rebuilding (while rebuilding the rear cylinder, calipers and installing new stainless brake lines), the piston in the master cylinder will not move in and out anymore after sitting for two days.

Does anyone have any suggestions:
1. as to how this happened, it worked fine right after rebuild?
2. what to do about it now?
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Re: How to rebuild your front master cylinder

Postby tyggerdude » Thu Mar 22, 2012 1:13 am

This doc was Great!!!! My dad used to do all my bike stuff, and I never took the time to learn. Now that I dont have him, I was lost without this docs guide to get the job done. Thanks again, couldnt have done it without you all :D
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Re: How to rebuild your front master cylinder

Postby WingAdmin » Thu Mar 22, 2012 12:04 pm

tyggerdude wrote:This doc was Great!!!! My dad used to do all my bike stuff, and I never took the time to learn. Now that I dont have him, I was lost without this docs guide to get the job done. Thanks again, couldnt have done it without you all :D


Great to hear this. I learned a ton from sitting next to my dad when he would work on the car, etc.
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Re: How to rebuild your front master cylinder

Postby thefrontsight » Sat Apr 14, 2012 12:49 pm

Alright....ive blead my front brake over and over.....Its acting like there is air in the line. Is this a sign that the front MS needs to be rebuilt? If the front brake lever is pumped i get a fistfull of brake. However, there are times when i squeeze the lever and it will touch the bar. (unlike a fist full of brake.) To rebuild or not rebuild that is the question. 1982 1100I 54k mi.
Michael
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Re: How to rebuild your front master cylinder

Postby WingAdmin » Mon Apr 16, 2012 11:51 am

thefrontsight wrote:Alright....ive blead my front brake over and over.....Its acting like there is air in the line. Is this a sign that the front MS needs to be rebuilt? If the front brake lever is pumped i get a fistfull of brake. However, there are times when i squeeze the lever and it will touch the bar. (unlike a fist full of brake.) To rebuild or not rebuild that is the question. 1982 1100I 54k mi.
Michael


Pump it up a few times until the brakes are good and hard, then while holding the brake lever in, wrap a bungee cord, rope, or something similar around it to hold the brake lever tight. Leave it like that overnight and see if it makes a difference for you.
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Re: How to rebuild your front master cylinder

Postby CharlaineC » Thu Jul 19, 2012 11:44 pm

thats what i did but i recently realized that the boot over the mc pisten is shot
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Re: How to rebuild your front master cylinder

Postby WingAdmin » Fri Jul 20, 2012 12:08 am

CharlaineC wrote:thats what i did but i recently realized that the boot over the mc pisten is shot


Any rebuild kit should supply you with a new boot:

Image
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Re: How to rebuild your front master cylinder

Postby Senior Bowler » Tue Sep 04, 2012 7:27 pm

My front brakes where soft so I rebuild system, had to replace 1 piston. I followed your great instruction I thought to a tee except when I got done the master cylinder will not pump any fluid.
I left it sit with brake lever tied down and with bleeder open still nothing.
Do you have any idea what would cause this?
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Re: How to rebuild your front master cylinder

Postby WingAdmin » Tue Sep 04, 2012 10:52 pm

Senior Bowler wrote:My front brakes where soft so I rebuild system, had to replace 1 piston. I followed your great instruction I thought to a tee except when I got done the master cylinder will not pump any fluid.
I left it sit with brake lever tied down and with bleeder open still nothing.
Do you have any idea what would cause this?


These bikes are notoriously hard to bleed when the master cylinder is not primed. The best way to do it is to use a vacuum bleeder on the caliper, and suck fluid down from the master cylinder. Once it's got some fluid moving through it, it will start being able to build up some pressure.
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Re: How to rebuild your front master cylinder

Postby Senior Bowler » Sun Nov 04, 2012 9:26 pm

Great write up on how to rebuild front master cylinder.
I followed insructions to the T , but after reinstalling the plastic cup for holding the fluid it leaks.
I cleaned o-ring channel well and o-ring looked good. It did not leak when I started. Knowing that the o-ring is the seal and looks do not make it good so I orderd a new one froom mother Honda.
After putting in new o-ring I still have leak, is there any kind of sealant that would work between cup and master cylinder and the brake fluid would not eat up?

I've taken a 1980 Gl1100 I apart, cleaning and replacing and damaged items. I have used many of the post from here to give me the knowledge to attemp this project. This has taken a lot longer than I imaged it would, but have been bonding with my wing


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