Brakes still out


Information and questions on GL1100 Goldwings (1980-1983)
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lowmanj
Posts: 52
Joined: Thu Dec 30, 2010 7:42 pm
Location: Merritt Island, FL
Motorcycle: 1981 GL 1100 Interstate

Brakes still out

Postby lowmanj » Fri May 13, 2011 9:55 pm



I rebuilt front brakes on my '81, but still no joy. New guts, reservoir and lever on master cylinder. All new lines and banjo bolts. Both calipers cleaned and rebuilt. I've bled 2 large bottles of fluid through it so far. Can't discern any more air comong out the bleeder valves. No leaks anywhere.
The lever depresses all the way. I see fluid movement in reservoir. If I open bleeder valves, fluid squirts out with force. But still, the piston won't push out from caliper far enough to get pad to roter contact.
I took the caliper off to observe. When I depress lever, the piston pushes just a bit, but returns to start point when the lever is released.
This chump is stumped.
Any ideas?
Thanks
Jesse



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RBGERSON
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Location: SCOTTSDALE, AZ
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had every year from 75 to 83

Re: Brakes still out

Postby RBGERSON » Sat May 14, 2011 7:33 am

Does the lever feel get harder if you pump it a bit? Does the lever compress all the way to the grip? New pads? sticking slide bolts on the calipers?
HAD LOTS OF GOLDWING 75-83
NOW INTO 1500'S..RIDING A 1998 SE

FAIR WINDS,
RB

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WingAdmin
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Re: Brakes still out

Postby WingAdmin » Sat May 14, 2011 8:18 am

It sounds like the pistons are hung up inside the caliper - you depress the lever, it pushes them out. Normally, because there's no resistance pushing them back in, when you release the lever, the master cylinder sucks more fluid in from the reservoir, and the piston stays put. The master then pumps that new fluid down to the piston on the next lever pull, pushing the piston out even farther.

In your case, something is causing the pistons not to want to push out - you pump the lever once, and when you let go, the piston returns to its original position, pushing the fluid back up to the master cylinder. All you're doing is pushing the pistons back and forth instead of pumping them out.

If I were to guess, I'd say perhaps one of the seals on the caliper is jamming against the piston. Did you lubricate the seals and pistons before reinstalling the pistons?

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eklimek
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Motorcycle: 81 GL1100 (Widowmaker not in service), 83GL1100, CB350f x 6, CB400f x2, CB550f sold, CL350 (seized engine), plus enough donors to take me through retirement.

Re: Brakes still out

Postby eklimek » Sat May 14, 2011 8:22 am

If calipers are not leaking fluid it's likely the master cylinder. I rebuilt mine (twice) after similar issues. I suspect the seal is not seated properly or is inserted incorrectly. It is inserted concave toward calipers.

A previous poster also suggested 1500 wet sand paper to smooth the walls. Please excuse the following directions if they seem trivial to you.

I used ATF/hydraulic fluid to wet the seals, filled the master cylinder with brake fluid before installation, and burped the handle bar banjo bolt before tightening. Use your thumb to close the master cylinder port when retracting the piston to fill the cylinder.

The last part is messy and full volumes are required with coordination of bleeder valve and lever. The air bleeder valve must be closed when the lever is released to draw fluid into the cylinder.

I never made substantial progress until the lines were under pressure and the compressed air audibly squirts out.

lowmanj
Posts: 52
Joined: Thu Dec 30, 2010 7:42 pm
Location: Merritt Island, FL
Motorcycle: 1981 GL 1100 Interstate

Re: Brakes still out

Postby lowmanj » Sat May 14, 2011 10:07 pm

You're on to something. I lubricated the seal only with ATF fluid. Should I have used grease or silicone?
But the most important detail I left out of original post; I re-used the old seal. I just ordered new seals and will see how that works.
Thanks very much!
Jesse

lowmanj
Posts: 52
Joined: Thu Dec 30, 2010 7:42 pm
Location: Merritt Island, FL
Motorcycle: 1981 GL 1100 Interstate

Re: Brakes still out

Postby lowmanj » Mon May 23, 2011 10:37 pm

Well, I installed new piston seals inspected and double checked the master cylinder parts while I was at it.
While disassembled, the piston moved easily with the new, lubricated seal.
The master cylinder parts were correctly installed, and seem to pump fluid as expected.
Still, no joy.
As before, the piston will push out then retract to starting point when brake lever applied and released.

I had installed new brake lines. New banjo bolts came with them, except for the double bolt. I'm starting to suspect the new lines don't match up with the old double banjo bolt.

Anyway, I read in another post here that I can depress the brake lever overnight and some air may work its way out.
I'll keep trying. One thing for sure, I have the freshest brake fluid around.
Thanks
Jesse

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eklimek
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Re: Brakes still out

Postby eklimek » Tue May 24, 2011 7:32 am

" the piston pushes just a bit, but returns to start point when the lever is released"

Is the brake lever "firm" or does it depress endlessly?

In the latter case, something is absorbing the pressure generated. If there is no more air, it may be a soft line. In either case a 8 mm fine thread metric bolt in the master cylinder in place of the banjo bolt will firm up the grip and you carry on eliminating the master cylinder.

In the former, as Wingadmin suggested, something is pushing/pulling the calipers back. I remain puzzled by this possbility. There is no compressible component in the calipers but for the seals and they are not positioned to do this. I take it you have removed the calpers , put a C clamp on the piston and observed the movement?

lowmanj
Posts: 52
Joined: Thu Dec 30, 2010 7:42 pm
Location: Merritt Island, FL
Motorcycle: 1981 GL 1100 Interstate

Re: Brakes still out

Postby lowmanj » Wed May 25, 2011 11:57 pm

Thanks for your help!

“Is the brake lever "firm" or does it depress endlessly?”
It depresses all the way, with no change in resistance level. It does push fluid. I see action in the reservoir and it pushes fluid out at bleed valve.

“ If there is no more air....”
To get all air out, I bled it a lot, cracked banjo bolts at MC and forks, and kept lever depressed overnight. I did not try mighty vac yet.

“,,,,it may be a soft line.”
I think this one is covered, with new, high quality lines.

“8 mm fine thread metric bolt in the master cylinder in place of the banjo bolt will firm up the grip and you carry on eliminating the master cylinder.”
Please explain a bit more. Once I install bolt, then what? And what should I be looking for?

“.... removed the calpers , put a C clamp on the piston and observed the movement?”
No, I’ve not. Should I, and to what end? I had calipers apart and well cleaned while rebuilding. Pistons moved fine manually. Just not under pressure as they should once assembled.

By the way, the left caliper brakes a little, just barely. On the left I see no light between pads and rotor, and it slows the wheel to a stop (front end off ground on jack stands). The right caliper has nothing for brakes.

Thank you again.
Jesse

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eklimek
Posts: 307
Joined: Tue Feb 15, 2011 1:55 pm
Location: St Catharines Ontario Canada
Motorcycle: 81 GL1100 (Widowmaker not in service), 83GL1100, CB350f x 6, CB400f x2, CB550f sold, CL350 (seized engine), plus enough donors to take me through retirement.

Re: Brakes still out

Postby eklimek » Thu May 26, 2011 8:32 am

Patience, perseverence and observation wil solve the problem.

Isolate the master cylinder and first make sure it is functioning properly.

Inserting a metric bolt in place of the banjo bolt removes the master cylinder from the system. Until you are certain it can develop pressure and cycles correctly the rest is guess work. If working properly vacuum assist is helpful only for priming the lines. You still need coordination, pressure and volume of DOT3 to purge the lines.

A "C" clamp on the piston caliper assemblies will allow the system to operate and observe the moving parts without full assembly required.

If the right piston is free air pressure at 90 psi is adequate to move the piston. A high pressure bicycle pump or shop air will work. Problem of obtaining an air seal I am sure you will solve. If 90 psi is inadequate the grease gun method is next but messy and involves more clean up.

lowmanj
Posts: 52
Joined: Thu Dec 30, 2010 7:42 pm
Location: Merritt Island, FL
Motorcycle: 1981 GL 1100 Interstate

Re: Brakes still out

Postby lowmanj » Mon May 30, 2011 9:59 pm

Thanks much.
If I understand the MC isolation part, I am looking to see that the brake lever is firm once the bolt is installed in place of the banjo bolt. That would verify that the MC is working as designed and rule it out as an issue. Right?
The c-clamp will allow me to work and trouble-shoot the system with the caliper off the bike for best observation, by preventing the piston from pushing out too far.
I know the pistons operate under pressure. The air hose pushes them right out on disassembly. I think the issue is that I’m not getting 90 PSI from my fluid sustem.
Thanks again and happy Memorial Day.
Jesse




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