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Hey All! , a little help please...

I am replacing the front pads on both sides and I can't get the middle piston on the left side to retract at all. All other 5 pistons up front are ready to go (flush) but this left middle one has me stumped. I've tried compressing the piston under pressure with the bleeder valve open to no avail. Both master cylinders are open to the atmosphere. I suspect it has to do with the Linked Brakes and the Delay valve. Surely someone has encountered this.

Thanks in advance,

Keith
(NCBirdMan)
 

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Welcome Carolina man.

Witch bleeder did U open as there are 2.
The center bleeder is for the center piston. This piston operates with the with the rear break.
The outer 2 pistons are used for the front break.
Yes U are correct it doe's have something to do with the linked system as this cycle has 2 master cylinders.
STex, out

how about some pix's of your machine.
 

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Hey South Tex,
Thanks for the response. Yes, I opened the center bleeder...as well as the other that bleeds the 2 outer pistons and the center bleeder on the right side since they are connected via the Delay valve. I know if I break the seal to the Delay valve this would relieve the pressure but I may have a leak at the fitting juncture upon retightening. There must be a way without compromising the system. This can't be a unique problem.
 

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Bottom line...the middle bleeder should relieve the pressure, it sure did on the right side but not the left....what's going on here?
 

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Bottom line...the middle bleeder should relieve the pressure, it sure did on the right side but not the left....what's going on here?
Sounds like a seized piston. Might be time to run a kit through the calipers.
 
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I've got a confession to make, I'm a serial piston cleaner!

I have never had to crack bleeders or any other part of the system in order to return that (or any other) piston so NCBirdMan I would suggest that Epoc's diagnosis of a seized piston is correct.
 
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I've got a confession to make, I'm a serial piston cleaner!

I have never had to crack bleeders or any other part of the system in order to return that (or any other) piston so NCBirdMan I would suggest that Epoc's diagnosis of a seized piston is correct.
Hey Duck, I'm a piston cleaner too! A clean piston is a clean mind. ;-)

Epoc, Commrad, and Duck, thanks for your responses.

This has been most vexing. When I removed the wheel to replace the tire I thought it was a good time to clean up the caliper and replace the pads. To expose the pistons I activated the levers pushing the pistons out somewhat. Once cleaned I could lube them and push them in without fear of trapping dirt in the slides. It was a good plan until ONE piston wouldn't retract. I got out my Mite Vac and it drew some fluid through the bleeder but stopped drawing fluid thereby creating a vacuum in the brake line (I heard the sound of air being sucked into the bleeder when I removed the vac. Unless there is a blockage between the rear pedal and the caliper I should be able to draw fluid. One possible explanation would be the Delay valve which lies between the pedal and left center piston. Prior to all this the left caliper wasn't dragging and seemed to be working perfectly. My new question is, if one extends the piston too far does this create a problem?...it worked on the others...vexing.

I'm going to keep at it and if all else fails I'll order the damn rebuilt kit. Again thanks for your help and offers. If anyone has any further ideas please post...I'm all ears.

Keith
 

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Discussion Starter #9
The return port in the rear pedal MC may be the culprit. Once I get everything sorted out I'll report my findings. In the meanwhile where do I find the necessary crushable washers for the banjos? K
 

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The crush washers are just std aftermarket items, nothing special, I bought a job lot of a 100 or so for a few $ some years ago .... stealers charge a fortune for them! Measure the banjo dia and you should be away (I always get the dias mixed up with the Brembo units that I run on my supercharged Bird so I won't quote figures off the top of my head!) ..... if you are really stuck and have a good condition washer you can always apply gentle heat and re-use ..... (not something that I would generally do but years of practical engineering has taught me a few 'tricks')

My new question is, if one extends the piston too far does this create a problem?...
there will be a small lead in and if the piston is pushed too far out there is a chance that it will not push in since the direction of force will not be perpendicular to the bore in the calliper.
 

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The crush washers are just std aftermarket items, nothing special, I bought a job lot of a 100 or so for a few $ some years ago .... stealers charge a fortune for them! Measure the banjo dia and you should be away (I always get the dias mixed up with the Brembo units that I run on my supercharged Bird so I won't quote figures off the top of my head!) ..... if you are really stuck and have a good condition washer you can always apply gentle heat and re-use ..... (not something that I would generally do but years of practical engineering has taught me a few 'tricks')

there will be a small lead in and if the piston is pushed too far out there is a chance that it will not push in since the direction of force will not be perpendicular to the bore in the calliper.
Right, heat annealing, got it...won't do it x-emergency.

Going out to begin the day anew, hope I meet with some success. Thx again Kwakster.
 

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The crush washers are just std aftermarket items, nothing special, I bought a job lot of a 100 or so for a few $ some years ago .... stealers charge a fortune for them! Measure the banjo dia and you should be away (I always get the dias mixed up with the Brembo units that I run on my supercharged Bird so I won't quote figures off the top of my head!) ..... if you are really stuck and have a good condition washer you can always apply gentle heat and re-use ..... (not something that I would generally do but years of practical engineering has taught me a few 'tricks')

there will be a small lead in and if the piston is pushed too far out there is a chance that it will not push in since the direction of force will not be perpendicular to the bore in the calliper.


Duck,
And we have a winner!

That was it, the piston was ever so slightly cock-eyed, a skewed or as they say around these parts caddywhompus. I was afraid to apply too much force using a tool so I just reached in from the side and using each index finger wiggled it as perpendicular as I could and squeezed for all it was worth. It went in smooth and I heard a "burp" in the line. After a good bleeding I trust I got the air out, I certainly got some gunk out until it ran clear.

Thanks for the good idea and other info. As you may have noticed I've been a member of this board since 2007. Just lurking and absorbing info, this is the first time I asked for help. You came through for me, I'll try to contribute more.

Keith
(NCBirdMan)
 
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