Rear Brake MC - Guts won't Come Out

Rear Brake MC - Guts won't Come Out

Postby WingMan71 » Mon Jun 02, 2014 7:03 pm

Hello all,

Newbie to the forum here. Still hunting for a CBX for my own, but I continue to help my best friend with his '82 CBX. He bought it new in '81, and still has it.

I have already searched the "Brakes" forum, but couldn't find an answer to my problem. So, I'm posting it up.

The rear brake MC is leaking from the shaft and also pretty crudded up mainly from sitting unridden for a year while he was moving and changing jobs.

He has a rebuild kit which I'm hoping to install. Had to soak the area around the snap ring (circlip) with PB Blaster for a few hours last night just to get it out today. Almost broke my snap ring pliers, but it's out.

I expected the guts to come out of the bore now that the snap ring is out, but nothing is coming out. I tapped on it a little bit, but still no go. So, I thought it best to stop there for the moment and seek advice from experts before I do something wrong and damage it.

So, how do I get the guts out of the MC bore now that the snap ring is removed?

HELP PLEASE!
1981 CB750C
2006 GL1800
1987 GL1200A
(U.S. Navy SWO - 1967 to 1976)
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Re: Rear Brake MC - Guts won't Come Out

Postby NobleHops » Mon Jun 02, 2014 7:26 pm

WingMan71 wrote:Hello all,

Newbie to the forum here. Still hunting for a CBX for my own, but I continue to help my best friend with his '82 CBX. He bought it new in '81, and still has it.

I have already searched the "Brakes" forum, but couldn't find an answer to my problem. So, I'm posting it up.

The rear brake MC is leaking from the shaft and also pretty crudded up mainly from sitting unridden for a year while he was moving and changing jobs.

He has a rebuild kit which I'm hoping to install. Had to soak the area around the snap ring (circlip) with PB Blaster for a few hours last night just to get it out today. Almost broke my snap ring pliers, but it's out.

I expected the guts to come out of the bore now that the snap ring is out, but nothing is coming out. I tapped on it a little bit, but still no go. So, I thought it best to stop there for the moment and seek advice from experts before I do something wrong and damage it.

So, how do I get the guts out of the MC bore now that the snap ring is removed?

HELP PLEASE!


Put some oil or WD-40 or whatever's handy down the other (banjo) end, let that soak, and then use a drift to gently tap on the end of the plunger to try and break it loose. The rubber seals within are more or less welded to the bore at the moment. Once it's free, you can use compressed air with a rubber tip to put a few puffs of air down the banjo end, but beware, that plunger is going to come out the other end at high speed if you're not careful and maybe even if you are. There are two rings in the end though - one plain ring that holds that condom-looking thing on and the proper circlip/snap ring in the groove. Are you quite certain both are out?
I Do Vapor Blasting! http://www.cbxclub.com/forum/viewtopic.php?f=5&t=9881

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Tucson, Arizona, USA '80 CBX, sort-of restored :-)

http://www.restocycle.com Ikon shocks for your CBX! https://www.ikonshocksusa.com/collections/honda/honda-cbx1000-79-80
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Re: Rear Brake MC - Guts won't Come Out

Postby WingMan71 » Mon Jun 02, 2014 7:34 pm

NobleHops wrote:... There are two rings in the end though - one plain ring that holds that condom-looking thing on and the proper circlip/snap ring in the groove. Are you quite certain both are out?


Nils,

I have only removed the snap ring at this point. Can you please give more detail on what/where this "plain ring that holds the condom-looking thing on" is?

I have removed the large rubber boot from the bottom that covers the shaft and the bottom of the MC where the snap ring lives. Is that what you're talking about?

Thanks for helping. Don't want to toast my friend's MC!
1981 CB750C
2006 GL1800
1987 GL1200A
(U.S. Navy SWO - 1967 to 1976)
WingMan71
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Re: Rear Brake MC - Guts won't Come Out

Postby NobleHops » Mon Jun 02, 2014 7:43 pm

WingMan71 wrote:
NobleHops wrote:... There are two rings in the end though - one plain ring that holds that condom-looking thing on and the proper circlip/snap ring in the groove. Are you quite certain both are out?


Nils,

I have only removed the snap ring at this point. Can you please give more detail on what/where this "plain ring that holds the condom-looking thing on" is?

I have removed the large rubber boot from the bottom that covers the shaft and the bottom of the MC where the snap ring lives. Is that what you're talking about?

Thanks for helping. Don't want to toast my friend's MC!


Sorry WingMan, I'm screwing you up speaking off the cuff. No such thing on the rear MC. I'm picturing a front.
I Do Vapor Blasting! http://www.cbxclub.com/forum/viewtopic.php?f=5&t=9881

Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

http://www.restocycle.com Ikon shocks for your CBX! https://www.ikonshocksusa.com/collections/honda/honda-cbx1000-79-80
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Re: Rear Brake MC - Guts won't Come Out

Postby WingMan71 » Mon Jun 02, 2014 7:55 pm

NobleHops wrote:Sorry WingMan, I'm screwing you up speaking off the cuff. No such thing on the rear MC. I'm picturing a front.


Nils,

OK, I'll follow the instructions in your first post and soak the insides in some PB Blaster over night.

Thanks very much!
1981 CB750C
2006 GL1800
1987 GL1200A
(U.S. Navy SWO - 1967 to 1976)
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Re: Rear Brake MC - Guts won't Come Out

Postby NobleHops » Mon Jun 02, 2014 8:04 pm

More fun I had:

viewtopic.php?f=50&t=8390&p=64334&hilit=rear+master+cylinder#p64334

Check that return orifice while you're in there!
I Do Vapor Blasting! http://www.cbxclub.com/forum/viewtopic.php?f=5&t=9881

Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

http://www.restocycle.com Ikon shocks for your CBX! https://www.ikonshocksusa.com/collections/honda/honda-cbx1000-79-80
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Re: Rear Brake MC - Guts won't Come Out

Postby steve murdoch icoa #5322 » Mon Jun 02, 2014 8:27 pm

When an overnight soak in PB had no results i applied a bit of heat from a propane torch to the m.c. body.
It allowed the PB to penetrate and the air blew the plunger out.
The paint was already messed up from the old brake fluid so a re-paint was in order anyways.
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Re: Rear Brake MC - Guts won't Come Out

Postby tevan » Mon Jun 02, 2014 8:48 pm

Hydraulic pressure------Find a bolt the size of the bolt the line bolts on with and drill a hole in the center of it all the way thru. Then tap it the size of a grease zerk and then screw a grease zerk in the bolt and hook your grease gun to it and pump away. It will push all the master cylinder guts out for you with no issues except you have to clean all the grease out of it when done. good luck :twocents-02cents:
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Re: Rear Brake MC - Guts won't Come Out

Postby WingMan71 » Tue Jun 03, 2014 9:58 am

I really appreciate all the advice and experience on this problem.

The PB Blaster loosened up the plunger and I can move the plunger shaft all the way in and out, so that's good. I still can't get the guts to pop out the bottom though.

I've currently got the MC filled up with PB Blaster and soaking for the day. When I get home from work tonight I'll fire up the air compressor and give it a shot.

I have another idea. Would this work...

Clamp the MC body in a soft-jawed vice. Then grab the weld nut on the plunger shaft with a vice grips or something similar and yank on it. Would that work to pop the guts out, or is that a bad idea?

? ? ?
1981 CB750C
2006 GL1800
1987 GL1200A
(U.S. Navy SWO - 1967 to 1976)
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Re: Rear Brake MC - Guts won't Come Out

Postby WingMan71 » Fri Jun 06, 2014 12:56 pm

THE GUTS ARE FINALLY OUT! :dance:

Compressed air would NOT even budge the guts on this thing. It was really toasty.

Finally had to clamp the MC in a vice and rig up a fixture that attached to the plunger rod and then tapped it out with a hammer! :shock:

Here's some shots to show you what I was up against.

Image

Pretty nasty!

Image

Here's cleaning the return port with a wire brush bristle inserted into a wooden match stick to hold it.

Image

Here's some shots after cleaning:

You can see that the return port hole is open now.

Image

Image

Here's the old guts and the new guts from the rebuild kit:

Image

QUESTION:

Do they really expect you to stretch that seal over the sharp edges on that metal piston piece to get in on there without cutting it?


Thanks for any advice on getting that seal on the piston.
1981 CB750C
2006 GL1800
1987 GL1200A
(U.S. Navy SWO - 1967 to 1976)
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Re: Rear Brake MC - Guts won't Come Out

Postby tevan » Fri Jun 06, 2014 1:38 pm

It will stretch over it and I have not screwed any up doing them.
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Re: Rear Brake MC - Guts won't Come Out

Postby steve murdoch icoa #5322 » Fri Jun 06, 2014 8:59 pm

Capital N nasty is right.
I was having trouble picturing your problem but not after seeing that photo.
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Re: Rear Brake MC - Guts won't Come Out

Postby barryadam » Sat Jun 07, 2014 12:59 am

Can't tell from your pictures, but how's the bore condition? Especially at the end nearest the snap ring? The seal wiper doesn't quite come all the way back when assembled. And how does the snap ring groove area look after your clean up?
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Re: Rear Brake MC - Guts won't Come Out

Postby daves79x » Sat Jun 07, 2014 7:06 am

Unfortunately, this is the condition of many m/cs we find today. You've done a good job of cleaning it, but I usually hone out the bore with a Scotchbrite ball on a Dremmel. There's a lot of crud in there and you need it perfectly clean to check for pitting, as has been mentioned. Usually the rear one doesn't pit much due to the vertical position of it. The Dremmel with a selection of brass wheels is also great for cleaning the cup and snap ring area as well.

When you get it done and working properly, change the brake fluid every two years and you won't have a problem.

Dave
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Re: Rear Brake MC - Guts won't Come Out

Postby NobleHops » Sat Jun 07, 2014 9:55 am

Great job getting that apart. What a PITA! Suspect your line and caliper might need the same treatment. I have one of these projects in my future as well. Warm that seal up for a minute with a hair dryer, might make it a tad easier to get on there.
I Do Vapor Blasting! http://www.cbxclub.com/forum/viewtopic.php?f=5&t=9881

Nils Menten
Tucson, Arizona, USA '80 CBX, sort-of restored :-)

http://www.restocycle.com Ikon shocks for your CBX! https://www.ikonshocksusa.com/collections/honda/honda-cbx1000-79-80
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