How to rebuild your front master cylinder


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Re: How to rebuild your front master cylinder

Post by WingAdmin » Sun Nov 04, 2012 8:38 pm



That O-ring is pretty standard, so you can match it up with a standard O-ring from any auto shop - as long as it is compatible with brake fluid.

That said, clean up the area and confirm where the fluid is actually leaking from. Try cleaning it up with brake cleaner, then dusting some talc (baby) powder in the area. This will show exactly where the leak is occurring. If it is the actual seal that's the problem, you'll be looking at re-cleaning the O-ring flange and seal, perhaps putting a slightly larger diameter O-ring (the diameter of the O-ring material, not the overall diameter), perhaps made of nitrile.

If the leak is above that, it's possible the plastic reservoir has developed a crack. The powder will reveal which is the cause.



dpmaughan
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Re: How to rebuild your front master cylinder

Post by dpmaughan » Sun Feb 17, 2013 11:19 am

I'm thinking of purchasing a complete master cylinder unit from eBay (K1motorcycles) - the cost seems very reasonable at $53. Does anyone have an experience with this type of application?

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Re: How to rebuild your front master cylinder

Post by B0b88 » Mon Mar 11, 2013 2:33 pm

Man that plastic piece of the master cylinder was hell to get off!! When you said it would resist you weren't kidding haha! Dpmaug I've seen the rebuild kit much cheaper, look on www.partsnmore.com www.jcwhittney.com or www.saber-cycle.com I forget which one had the best price of the Kl rebuild kit.

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Re: How to rebuild your front master cylinder

Post by WingAdmin » Mon Mar 11, 2013 5:17 pm

B0b88 wrote:Man that plastic piece of the master cylinder was hell to get off!! When you said it would resist you weren't kidding haha! Dpmaug I've seen the rebuild kit much cheaper, look on http://www.partsnmore.com http://www.jcwhittney.com or http://www.saber-cycle.com I forget which one had the best price of the Kl rebuild kit.
Even if Saber Cycle has the best price, you're better off not using them. Do a search on their name here if you want to find out why, or have a look at the user comments on their vendor record: http://goldwingdocs.com/Vendors/Saber-Cycle_880

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Re: How to rebuild your front master cylinder

Post by bykerbiker » Wed Apr 24, 2013 12:53 pm

Hi on the subject of priming the master cylinder ,I used a large syringe [that I had used previously topping up front forks on another bike ],I connected it to the bleed nipple with a bit of hose from wiper blades and it sucked the fluid down and disconnecting it to return the plunger into the body of the syringe after a number of strokes. Priming the master cyl and also a lot of air bubbles.It proved very good, saved buying a vaccuum device . I had polished the pistons in the caliper clearing the return hole with a bit wire it felt gritty and that now seems to have solved my problems witgout renewing the master piston etc. Once again the instructions in the HOW TO were invaluble. As until I re read the instructions I thought the master was needing renewing
but only needed priming.

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Re: How to rebuild your front master cylinder

Post by jhbates2000 » Mon Sep 09, 2013 11:57 am

I just rebuilt my front master cyclinder...twice cause I thought I did something wrong the first time. I put brake fluid in it and tried to pump it up and all the brake handle does is hit the handle bars. It will not pump up for nothing what did I do wrong and where do I go from here? Very frustrated at this point. :(

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Re: How to rebuild your front master cylinder

Post by WingAdmin » Mon Sep 09, 2013 12:42 pm

jhbates2000 wrote:I just rebuilt my front master cyclinder...twice cause I thought I did something wrong the first time. I put brake fluid in it and tried to pump it up and all the brake handle does is hit the handle bars. It will not pump up for nothing what did I do wrong and where do I go from here? Very frustrated at this point. :(
They do not prime easily, which is the problem you're encountering.

What I do is put a suction pump on the bleeder valve (i.e. a Mity-Vac). That sucks fluid through the innards of the master cylinder and down the brake line to the caliper. Once you've got fluid past the master cylinder and moving down the line, you should be able to pump the handle. At that point, the more pumping you do, the more air you remove. I pump slowly, holding the handle in for a few seconds each time, then let it release slowly, letting the bubbles work their way up and out.

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Re: How to rebuild your front master cylinder

Post by jhbates2000 » Mon Sep 09, 2013 1:39 pm

I dont own a mity vac..got any suggetions on something else to use?

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Re: How to rebuild your front master cylinder

Post by WingAdmin » Mon Sep 09, 2013 3:12 pm

You can try filling the master cylinder reservoir with fluid, then pulling the lever back and tying it there with a bungee or some string. Put the cover on the reservoir (you don't want brake fluid exposed to the air for too long, as it will suck moisture out of the air) and let it sit for a few hours. There's a fair chance the fluid will migrate down into the cylinder enough to get a prime, so that you can then pump it down to the caliper.

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Re: How to rebuild your front master cylinder

Post by jhbates2000 » Thu Sep 12, 2013 12:00 am

Soooo heres the deal, I was never able to get the mastercyclinder to prime, not really sure why. But I was able to pick up a nearly complete 83 1100a to use as a parts bike. There were a few things missing off of it but not much. On the bright side it has 2 brand new tires on it which means it pretty much paid for its self since I was able to get it for $300.00. It has a ton of parts that I may need or may be willing to get rid of for a good price. I said all that to say I ended up taking the front master cylinder off the parts bike and put it on mine and it worked like a charm.

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Re: How to rebuild your front master cylinder

Post by seelyark1 » Sat Mar 29, 2014 7:48 pm

WingAdmin wrote:You can try filling the master cylinder reservoir with fluid, then pulling the lever back and tying it there with a bungee or some string. Put the cover on the reservoir (you don't want brake fluid exposed to the air for too long, as it will suck moisture out of the air) and let it sit for a few hours. There's a fair chance the fluid will migrate down into the cylinder enough to get a prime, so that you can then pump it down to the caliper.
Pushing the piston past the compensating port will not let fluid go past the piston and into the brake line. Just letting it sit with the compensating port open will let brake fluid enter the brake system. Just opening the bleeder valve will let gravity help get fluid into the line and past the piston faster.
Ride safe, and smart. Asphalt is like #1 grit sandpaper. Dave

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Re: How to rebuild your front master cylinder

Post by morriscatt » Sat Jun 07, 2014 8:43 am

Another very good How To. Thank you.
I am curious however, where the washer that came with my rebuild kit goes?
Patrick

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Re: How to rebuild your front master cylinder

Post by WingAdmin » Sun Jun 08, 2014 10:24 pm

morriscatt wrote:Another very good How To. Thank you.
I am curious however, where the washer that came with my rebuild kit goes?
Patrick
It depends, what does it look like? Is it possible it is a replacement washer for the banjo bolt?

Image

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Re: How to rebuild your front master cylinder

Post by jgm8806 » Thu Jun 11, 2015 10:38 am

Question, I just bought a 81 GL 1100 Wing and Im rebuilding the Front Master Cylinder…The kit the guy bought who owned the bike gave it to me…I have everything torn down and I opened the kit ..The spring that goes behind the plunger doesn't have a hole in it…it is a solid metal cap …Is this ok to use or should I re order a new kit…
1987 Aspencade, one owner, 17000 original miles.

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Re: How to rebuild your front master cylinder

Post by WingAdmin » Thu Jun 11, 2015 10:53 am

jgm8806 wrote:Question, I just bought a 81 GL 1100 Wing and Im rebuilding the Front Master Cylinder…The kit the guy bought who owned the bike gave it to me…I have everything torn down and I opened the kit ..The spring that goes behind the plunger doesn't have a hole in it…it is a solid metal cap …Is this ok to use or should I re order a new kit…
If the rubber part that seats on that cap has a small piece to fit in that hole, then you might want to drill a small hole in that cap for it to fit properly. If it doesn't, I'd just use it as is and call it good. That hole is just meant to keep the rubber piece centered more or less.

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Re: How to rebuild your front master cylinder

Post by jgm8806 » Thu Jun 11, 2015 10:58 am

Ok, Rubber Cap is flat with no nipple, The kit is made by K&L kit # 32-1102 …Other reference is MSB- 105….You familiar with this company...
1987 Aspencade, one owner, 17000 original miles.

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Re: How to rebuild your front master cylinder

Post by jgm8806 » Thu Jun 11, 2015 11:04 am

Must be the wrong kit..Plunger is 1inch longer than original…Sorry to waste your time and Thanks for the reply…Jim
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Re: How to rebuild your front master cylinder

Post by jgm8806 » Thu Jun 11, 2015 11:07 am

Kits for the rear Master Cylinder …So Ill have to order the Front…Thanks….
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Re: How to rebuild your front master cylinder

Post by velvetrider » Mon Nov 02, 2015 4:27 pm

If ya read all the post under this topic: There is a #1 tip/trick that DWSINCLAIR made. Remove one of the caliper bolts and lift caliper so bleeder is close to the vertical,,,careful not to pull pads off rotor. Then bleed them.. I have just installed new braided lines, mainly because front brake was Squishy..;no matter how many times I bled the damn thing. I did may normal bleed of front brakes with the new line on, expecting a 'fist full' of brake. Same Squishy feel. Did the # 1 tip/trick, pulled a caliper bolt, raised the caliper so bleeder was close to vertical the remove that MADDENING air bobble, It worked. I now have a FIST FULL. I may not have bought the new braided lines had I known this trick. Back to the rebuild.

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Re: How to rebuild your front master cylinder

Post by mlmaher » Tue Sep 20, 2016 9:59 pm

My pressure relief hole is totally blocked. I'm using a jet cleaning tool but not getting anywhere. Any ideas? Oh and the o ring for the reservoir it seems to me that the only way to know that it is safe to use with brake fluid is to get an original honda o-ring. Does anyone know of any safe alternatives? Thanks

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Re: How to rebuild your front master cylinder

Post by WingAdmin » Wed Sep 21, 2016 9:32 pm

mlmaher wrote:My pressure relief hole is totally blocked. I'm using a jet cleaning tool but not getting anywhere. Any ideas? Oh and the o ring for the reservoir it seems to me that the only way to know that it is safe to use with brake fluid is to get an original honda o-ring. Does anyone know of any safe alternatives? Thanks
If you can find a nitrile O-ring that will fit, that will work fine.

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Re: How to rebuild your front master cylinder

Post by Johnyy Smoke » Sat Feb 04, 2017 5:21 pm

morriscatt wrote:Another very good How To. Thank you.
I am curious however, where the washer that came with my rebuild kit goes?
Patrick
I noticed this also. The washer goes on top of the piston and the "D**n hard to get in circle clip" is placed on top of the washer. At least this is how mine was when I took it apart. Perhaps the bikes with the plastic (not metal) diaphragm are made this way? Regards, Johnny

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RE: MC rebuild. How to get the seal onto the piston?

Post by mytown » Fri Aug 11, 2017 5:35 pm

Any tips for getting the seal over the lip? It is way tight where it is.



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Re: How to rebuild your front master cylinder

Post by seelyark1 » Sat Aug 12, 2017 10:08 am

Take some tin lead solder and mash it into the groove till it is full. File it till it is the same size as the shaft. Seal should slide over it. Use a large size solder to fill the groove. Use this method on aircraft struts, should work here too.
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Re: How to rebuild your front master cylinder

Post by WingAdmin » Tue Aug 15, 2017 11:11 pm

seelyark1 wrote:
Sat Aug 12, 2017 10:08 am
Take some tin lead solder and mash it into the groove till it is full. File it till it is the same size as the shaft. Seal should slide over it. Use a large size solder to fill the groove. Use this method on aircraft struts, should work here too.
Wow, what a great idea!

I just used lots of lube and gently stretched it over the piston, but I really like your method.



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