Rear master cylinder predicament


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maintainer
Posts: 291
Joined: Sun Mar 22, 2015 11:39 am
Location: Houston, Texas
Motorcycle: 1977 GL 1000
1982 GL 1100 Interstate (Sold)

Rear master cylinder predicament

Post by maintainer »



On my GL 1000 project bike, I am getting down to the short lists. One item was to go thru everything on the rear brakes and pedal pivot etc.
The single thing I lack doing is rebuilding the rear master cylinder, it was in just awful condition. (corrosion)
The rear master cylinder which is very similar to but not exactly like the GL1100 one on the forums video tutorial.
Problem is, evidently the piston is stuck in the bore.
I have soaked it in PB blaster, tapped on it hoping it would spring outward, shot compressed air to the back side of it.

Nothing has worked. I'm to the point of drilling into it and using an ease out bit.

Any idea's before I go all radical on it?????


1982 GL 1100 Interstate SOLD
1977 GL 1000 Standard (naked can be good, who knew?)
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spiralout
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Motorcycle: 1975 GL1000 (gone)
1980 GL1100I (with '77 1000 engine)
1996 GL1500 SE

Re: Rear master cylinder predicament

Post by spiralout »

If the banjo fittings are the same size, take your front brake line off the splitter, bolt it to the rear master and use the front to pump it out.
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maintainer
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Motorcycle: 1977 GL 1000
1982 GL 1100 Interstate (Sold)

Re: Rear master cylinder predicament

Post by maintainer »

spiralout wrote:If the banjo fittings are the same size, take your front brake line off the splitter, bolt it to the rear master and use the front to pump it out.
Nope, rear line is a thread in line with no banjo fitting.
My fronts are all new and rebuilt but I haven't added and brake fluid or bled them out yet.
1982 GL 1100 Interstate SOLD
1977 GL 1000 Standard (naked can be good, who knew?)
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spiralout
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1980 GL1100I (with '77 1000 engine)
1996 GL1500 SE

Re: Rear master cylinder predicament

Post by spiralout »

Yep, I was thinking of the 1100 rear master, sorry :cry:
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ankgrays
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Motorcycle: 1981 GL1100 interstate

Re: Rear master cylinder predicament

Post by ankgrays »

I had a similar problem with my '81

Someone suggested taking out the brake bleeder and putting on a compressed air hose as tight as

you can hold it on. Then hit the air lever...popped right out.

Be careful to have the piston aimed at something soft so as to keep it from shooting across the floor.

Good Luck!!
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maintainer
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Motorcycle: 1977 GL 1000
1982 GL 1100 Interstate (Sold)

Re: Rear master cylinder predicament

Post by maintainer »

ankgrays wrote:I had a similar problem with my '81

Someone suggested taking out the brake bleeder and putting on a compressed air hose as tight as

you can hold it on. Then hit the air lever...popped right out.

Be careful to have the piston aimed at something soft so as to keep it from shooting across the floor.

Good Luck!!
Sounds like an idea.
So just so I understand, I shouldn't look down the bore at the top of the piston and apply high pressure air to it? :P :D
1982 GL 1100 Interstate SOLD
1977 GL 1000 Standard (naked can be good, who knew?)
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maintainer
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Motorcycle: 1977 GL 1000
1982 GL 1100 Interstate (Sold)

Re: Rear master cylinder predicament

Post by maintainer »

Ok I went radical and got it out with no damage to the bore.
1. I carefully drilled a pilot hole in the top of the piston.
2. I followed up with a larger bit which wedged in and spun the piston, and out came all the guts.
Cleaned up the mucky nasty bore.
Ready for rebuild kit.

It's a shame a rebuild kit with a piston some rubber bits and a spring are $50. :shock:
1982 GL 1100 Interstate SOLD
1977 GL 1000 Standard (naked can be good, who knew?)
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spiralout
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1980 GL1100I (with '77 1000 engine)
1996 GL1500 SE

Re: Rear master cylinder predicament

Post by spiralout »

maintainer wrote:Ok I went radical and got it out with no damage to the bore.
1. I carefully drilled a pilot hole in the top of the piston.
2. I followed up with a larger bit which wedged in and spun the piston, and out came all the guts.
Cleaned up the mucky nasty bore.
Ready for rebuild kit.

It's a shame a rebuild kit with a piston some rubber bits and a spring are $50. :shock:
Agreed. I think I paid 35 bucks to vtcustoms ebay store for the rear master kit for my '80, and that was about $20 too much for what it is, in my opinion.
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maintainer
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Motorcycle: 1977 GL 1000
1982 GL 1100 Interstate (Sold)

Re: Rear master cylinder predicament

Post by maintainer »

Here's a couple of pictures of the carnage.




1982 GL 1100 Interstate SOLD
1977 GL 1000 Standard (naked can be good, who knew?)
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redial
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Re: Rear master cylinder predicament

Post by redial »

That drill does not look too radical! But some of the other bits look somewhat sad! :shock:
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gc33
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Motorcycle: 1981 Gl1100 naked.

Re: Rear master cylinder predicament

Post by gc33 »

Same problem with my 1100. and of course scarce as hens teeth. And it would seem every wing from 1000's to at least 1100's have had same problem with the rear master cylinder. Im currently looking for a replacement fuel tank (there are quite a few on ebay..its the shipping that hurts me) and almost every one I look at has the paint missing in that same area the master sits.
Anyway, Ive bought a new cyl off ebay, its not a wing one, its one of those kinda generic type ones that can go on any bike.But at $16aus I figured id give it a go. If it works great, if not, its only $16. As you guys have mentioned, the rebuild kits are pretty ridiculously priced, as are caliper rebuild seal kits and as I cant seem to get anything here in Australia I have to get from UK or USA. And again, between exchange rates and shipping its a killer. brake crafters are $32US for a rear cyl rebuild kit, thats $50 in our money. and about the same for front rebuild kit.
I have been told, and Im yet to investigate true or not, and how much, but apparently there is a brake place here in perth WA that will re-sleeve the cylinder with a stainless sleeve. I have a feeling its gonna be in the $80 mark to have done. Expensive but trying to replace that master is almost impossible. One of the parts suppliers I was in contact with in USA reckoned he could sell 1 a day...Kinda tells me the cylinders a a bit crappy if everyone wants them..same problem I guess.
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pidjones
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1978 GL1000 w/'75 engine (project)

Re: Rear master cylinder predicament

Post by pidjones »

Please pull that new Chinabay MC apart, clean thoroughly, and assemble properly with brake fluid lubricating it before use. I bought both a front and rear to adapt and use on a CB750F, and they were both filthy inside. After cleaning and proper assembly they worked fine, however.
GWCox
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Motorcycle: 1978 GL1000 Gold Wing

Re: Rear master cylinder predicament

Post by GWCox »

I needed to rebuild the rear master cylinder on my 1978 GL1000 and so have read just about everything I could find on the subject. There seems to be a lot of misinformation out there about how to access the small return port for cleaning.

First, my story in how I got the piston out of the master cylinder. I tried all of the suggested methods, forcing it out with compressed air, drilling into it and having the drill bit eventually spin it out, etc., but none of these worked for me. I ended up drilling into the piston with successively larger drill bits until I could get an easy-out to thread into it. The easy out had some grooves in the shaft which I could catch with a screwdriver, so screwdrivers on each side got the piston pried up to the top of the bore but no farther. I then clamped the end of the easy-out in a vise and used a rubber mallet gently on the master cylinder body tapping in a direction away from the vise and soon the piston popped right out.

Now for the small return port. Lots of blogs on this subject state that the master cylinder reservoir must be removed to access the port. This supposedly becomes an issue because the reservoir is difficult to remove (I spent a lot of time trying unsuccessfully without becoming destructive) and it cannot be found as a separate part to replace if damaged. However, I found that the removal of the reservoir is absolutely not required to access and clean the port. In fact, removal will not help at all in the case of the rear master. There is a block-off plug located on the back side of the master cylinder (as it is mounted on the bike). Once this block-off plug is removed, you can look straight down through the access hole to where the small port goes into the piston chamber.

The attached pictures show:
1. a shot of the piston bore with a cleaning wire extended through the port into the bore. At the top you can see the same wire extending out of the access port.
2. a shot showing the location of the access port (where the block-off plug was) on the back of the master cylinder with the same cleaning wire still extending out of it.
3. a shot looking straight down the access hole where you can see the cleaning wire extending through the small return port into the cylinder bore.

Hope this saves someone else some time and angst.

GWCox
Humble, TX
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Rambozo
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Re: Rear master cylinder predicament

Post by Rambozo »

A non destructive way to get out a stuck piston, is to use a grease gun. Make up a fitting to attach to the line and pump it right out. Your typical grease gun can reach 10,000 psi, or more. And grease is non compressible, so much less danger than high pressure air, when it finally lets go.


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