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Hey all...

I suspect I have a clogged relief port in my rear master cylinder (brake pads don't retract far enough when rear brake pedal is released which causes them to drag). I checked all the linkages to see if they were free and they are so nothing is hanging up there.

I had this happen once on my front brakes and that microscopic relief port hole was visible looking down through the reservoir. I unclooged it by pushing a guitar high "E" string into it and it is fine now.

Is that hole right under where the brake fluid line enters the rear master cylinder coming from the rear brake reservoir...if not, does someone know exactly where it is?

Thanks!
 

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if you have the plastic hose connection pice off the master --and look inside the port you can see 2 holes a small one near the top and a larger one about center .the small hole is the one in question . at least thats what i see on my 83.
 

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A few other things to check that could cause it to dragor not return;



1. Some bike models have an adjustment screw (on the brake lever)to control the downward starting position of the brake lever....make sure that the lever is not so far down that it is applying the brake.



2. Some models have an adjustable rod between the master cylinder and the end of the brake lever......make sure that the rode is not so far out that it causes the brake to apply also.



3. Inspect the caliper piston and make sure that it is not rusty - (may have to remove the brake pads and carefully lift the rubber seal (around the piston) to view the piston.
 

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Discussion Starter · #4 ·
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Thanks guys...



I checked all the linkages and they all seem to be fine...that was my first inclination. The rear brake caliper was rebuilt late last year thinking that the issue might be with either the seals or the pistons but it's still doing the same thing.It has new seals and thepistons looked to be fine. So either the issue is a clogged port (relatively easy toremedy) or a master cylinder rebuild (not so easy but certainly doable if necessary).



I'm off to check things out....
 

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I have a 1000 and had been fighting rear mc problem for a couple months. I don't know how close the cylinders are to one another. Mine had a 14 mm headed bolt which intersected the area under the reservoir and had a small port into the bore of the mc. A smaller yet port entered the bore about 3/16" deeper (further along the bore). I attempted to clear mine by inserting different wires into the port. Didn't work. I had mine off to locate the smaller port. I looked into the bore for days. I finally found the port. I had been overlooking it all the time.

I accessed the smaller port through the hole where I had removed the above mentioned bolt. It was straight in almost online with the larger bolt. It starts out 3/16" to 1/4", then steps down to minuscule. Try inserting your "E" wire there.

I wasn't able to get this to work for me. I posted the task under another thread. I will locate it and post link here with and edit.

Terry

Try: http://goldwingfacts.com/forums/forum1/67593.html
 

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I recently had some practice unclogging mine.

I whittled down a wire from a wirebrush to 0.25mm (0.010")
 

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Stuck it in the li'l hole:
 

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And it eventually comes out here!!
 

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Discussion Starter · #9 ·
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Gents,



Thanks for all your help...I installednew pads in my calipers this afternoonas they were worn down from not coming away completelyfrom the disk when brake pedal was released.



Ilooked at the pistons in the caliper and they looked OK; not rusty, just dirtyso I cleaned them up and pushed them home, put the pads in and reassembled the caliper and reinstalled it.



I went to the other side of the bike and removed the master cylinder and found a bunch of"crud" in thebowl like areawhere the line comes down from the reservoirinto the cylinder. I cleaned all that out with fresh fluid and blew it out with compressed air and found the tiny hole in the bottom of the forward port. I cleaned that out (it seemed open but hard to tell), cleaned up the master cylinder, and reinstalled it. I filled the reservoir and bled the system. I get good hard brakes but the pads are still dragging some on the discs. I'm at a loss as to what to do next.



Pete at Venco rebuilt the calipers late last year so I doubt it's that. I haven't actually torn the master cylinder down completely and rebuilt it but I am of the thought that if I am getting good bleeds and hard brakes, it's probably not that...but maybe it is.



I flushed all the old fluid out today and fluid throughout system is clean/clear...



Maybe a MC rebuild is in the cards...
 

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when was the last time you adjusted or replaced the pad spreader springs ? the one that puts tension on the pads when just going down the road.
 

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Discussion Starter · #12 ·
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wda-83wing wrote:
when was the last time you adjusted or replaced the pad spreader springs ? the one that puts tension on the pads when just going down the road.
When the caliper was rebuilt last year.



I think I might head over to Venco Wings Monday and pick up a rebuild kit...



this whole thing really sucks because it's bike week here in NH and the weather has been so friggin' crappy the past 2 months that there has been no time to fix this problem :X...now the weather has finally broken a bit for the better and I have to spend that time trying to fix a rear brake problem instead of out riding with the throngs.



I don't think my wife would appreciate me dragging the bike into the livingroom to work on it...brake fluid on a varnished pinefloor probably isn't real good for it :(.
 

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Timmus my 82 gets contrary on dragging the rear pads once in awhile. I cleaned and shined on the pistons, lubed and pushed the pistons in and out sevral times before it freed up enough to quit dragging. Several have posted that the groove in thecaliper cylinder where the o ring fits had a varnish orcrud build up and had not gotten completely cleaned on the rebuild causing the o ring to grab the piston so tight it didn't relax when pressure was released. Read some where on thepost that wearing uneven was sign that slider bolts and sleeves were dirty and binding. hope you find it with out muchaggrivation.
 

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aaahhhhh heck all you got to do is remove the pins and spread the springie part a little and put them back togather.
but i can see the problem with doing that on a varnished floor-----got to keep ma ma happy.
 

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Discussion Starter · #15 ·
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the slider bolts and sleeves are all free. The pistons were pretty free this afternoon when I pushed them home to install the new pads...When Pete rebuilt them last summer, I watched him do it (so I'd know how to do it next time) and he was very careful to get all the crud out of those grooves that the rubber ring seals went into. He polished the pistons before he installed them and so I assuming that the caliper probably isn't the problem at this point...of course we all know what happens when we assume;)
 

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Wayne if mine drags again I'll go straight to your fix. Thanks for the heads up:waving:Ken
 

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Timmus wrote:
I cleaned all that out with fresh fluid and blew it out with compressed air and found the tiny hole in the bottom of the forward port. I cleaned that out (it seemed open but hard to tell),

If you don't have a 0.010" wire, and you have removed all the rubber bits from the cylinder, you can squirt it with carb cleaner. You will see it squirt throught the little hole and know for sure it is clear. You need to make sure all the seals are removed first as the carb cleaner will eat them.
 

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Actually, I'm pretty sure that tiny hole is cleaned out. I used a .010 guitar string to make sure it was clear and the wire went clear through. When I held my compressed air nozzle (a 4" long hollow tube about the diameter of a ballpoint pen ink refill)up to the holeand blew air through it, it wasobvious from the fluid coming out of the cylinder that the air was getting through it.
 

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With the brakes dragging, loosen a brake line to relieve pressure.

If it still dragging with the pressure released, then you know it is something mechanical and not hydraulic.
 

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Discussion Starter · #20 ·
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maplewingnut wrote:
With the brakes dragging, loosen a brake line to relieve pressure.

If it still dragging with the pressure released, then you know it is something mechanical and not hydraulic.
great idea...I'll break open the banjo bolt on the master cylinder tomorrow and see what happens...
 
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