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Discussion Starter · #1 ·
My first message since returning to the fold Other than the New member thing.
I have bought back my old 2001 Blackbird that the insurance company sold after an accident and one of the first thing I did was fit jaws de-linking brake kit. Fitted it with only a modicum of naughty words and was happy with it. Last winter had the rear caliper and MC rebuilt using Honda parts but the rear brake was still sub par so got a new Brembo disc and fitted it. Had been working but poorly and recently the brake seized up, the middle piston had not retracted and had burnt through the pad and welded itself to the pad. I have no idea as to why this should have happened, the middle piston was replaced with Honda part, system bled properly. Anyone have any ideas and or advice - would be much appreciated!
Thanks, Michael
 

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Hmm my first stab at it lol, erm if you have delinked the brakes then theres no secondary master cylinder to mess with or pcv valve, so hmm if you had the rear brake master cylinder rebuilt, makes me wonder if the small reservoir passageway is clear, it's only a small hole in the body of the master cylinder, the only other thing is were the caliper piston seal land spotless?, so the seals are sitting right, I've had crap on a bike a few years ago, and the piston seal lands in the caliper body still had crud on them, causing the piston not to retract properly.
So I think it's either the return hole on the master cylinder slightly blocked, or crud on the piston seal groves.
 

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Could also be the piston seals.
It is the piston seals that retract the pistons - they distort slightly when you apply the brakes.
Then pull the piston back as they regain their shape.
This is why pistons are much easier to push in to a caliper than they are to pull out.
Once the seals lose their sharp edge - they do not pull the piston back like they are designed to do.
 

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Discussion Starter · #4 ·
Hmm my first stab at it lol, erm if you have delinked the brakes then theres no secondary master cylinder to mess with or pcv valve, so hmm if you had the rear brake master cylinder rebuilt, makes me wonder if the small reservoir passageway is clear, it's only a small hole in the body of the master cylinder, the only other thing is were the caliper piston seal land spotless?, so the seals are sitting right, I've had crap on a bike a few years ago, and the piston seal lands in the caliper body still had crud on them, causing the piston not to retract properly.
So I think it's either the return hole on the master cylinder slightly blocked, or crud on the piston seal groves.
Thanks, will check that small hole and have new seals are on order to replace the old "new" seals so hopefully that might do the trick.
Could also be the piston seals.
It is the piston seals that retract the pistons - they distort slightly when you apply the brakes.
Then pull the piston back as they regain their shape.
This is why pistons are much easier to push in to a caliper than they are to pull out.
Once the seals lose their sharp edge - they do not pull the piston back like they are designed to do.
Could also be the piston seals.
It is the piston seals that retract the pistons - they distort slightly when you apply the brakes.
Then pull the piston back as they regain their shape.
This is why pistons are much easier to push in to a caliper than they are to pull out.
Once the seals lose their sharp edge - they do not pull the piston back like they are designed to do.
Could also be the piston seals.
It is the piston seals that retract the pistons - they distort slightly when you apply the brakes.
Then pull the piston back as they regain their shape.
This is why pistons are much easier to push in to a caliper than they are to pull out.
Once the seals lose their sharp edge - they do not pull the piston back like they are designed to do.
Thanks for you suggestions, to be honest I was a bit suspicious of the work done by the shop but figured they would know more than me about the brakes which is an area of which I am somewhat intimidated.
 

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After that you only have the actual mastercylinder piston seals if it carries on dragging, but do the hole thing and the seals in the caliper first.
One point though, if you do go down the route of a mastercylinder seal rebuild kit, from what I have gathered there are 2 after market kits, I got the wrong one a few last year, didnt realise until I opend the box and started fitting it.
If you have the funds I would go OEM on a mastercylinder rebuild kit to make sure you get it right first go.
 

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Discussion Starter · #6 ·
After that you only have the actual mastercylinder piston seals if it carries on dragging, but do the hole thing and the seals in the caliper first.
One point though, if you do go down the route of a mastercylinder seal rebuild kit, from what I have gathered there are 2 after market kits, I got the wrong one a few last year, didnt realise until I opend the box and started fitting it.
If you have the funds I would go OEM on a mastercylinder rebuild kit to make sure you get it right first go.
Thanks bikerian, I bought an OEM Honda rebuild kit for the rear master cylinder so am assuming that is good but Aareally good mechanic whom I trust is going to rebuild both caliper and MC, I will mention all the advice that has been given, but the small hole being blocked could well be the culprit.
Thanks again. Michael
 

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Thanks bikerian, I bought an OEM Honda rebuild kit for the rear master cylinder so am assuming that is good but Aareally good mechanic whom I trust is going to rebuild both caliper and MC, I will mention all the advice that has been given, but the small hole being blocked could well be the culprit.
Thanks again. Michael
there is a very smalll hole in the bore of the rear m/s if it's blocked it can cause the rear caliper to stay on
 

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That is typically the Secondary master Cylinder on the left fork leg.
Never had any issues with blocked holes in the rear master
Corrected me if iam wrong, but I think he has them delinked, other wise yes I would go to secondary master cylinder.
I did have a blocked hole lol, on my rear master cylinder, my brakes were badly neglected when I got mine, it was like white fine sand, I think it was reminence from ptfe tape.
 

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Anyone have any ideas and or advice - would be much appreciated!
Couple of thoughts.

1. Any chance the rear pedal has been adjusted and the pushrod is now holding the piston in very slightly on the rear master ?

2. If you are still using the standard rear master ( 17.5mm bore ) on a de-linked bike - I am not surprised it feels sub par.
Many have fitted the 12.7mm master from a CBR125R or the 14mm master from a CBR300R to correct the hydraulic ratio and give the rear brake the feel that other non linked bikes have.
 

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my 98 had done 82000 kms and then sat for 8 years when i got it the back brake kept staying on , i de-linked it and ran 2 lines to the rear pistons from the standard master cylinder and once the new pads had run in it stops and slows really well and the small hole in the bore was blocked and there was a whitish colored residue through out the bore and piston but there was no sign of any tape having been used
 

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my 98 had done 82000 kms and then sat for 8 years when i got it the back brake kept staying on , i de-linked it and ran 2 lines to the rear pistons from the standard master cylinder and once the new pads had run in it stops and slows really well and the small hole in the bore was blocked and there was a whitish colored residue through out the bore and piston but there was no sign of any tape having been used
Might have dissolved what little ptfe tape you had, just leaving behind a small residue.
I had it on my bleed nipple threads what actual old recognisable tape there was, so I knew some one had been using it on mine, gits lol.
 

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Cheers all,

I'm no expert on delinking but I have read that the rear caliper needs extra passageways drilled to make all three pistons work after delinking and removing the DCBS master from the left front fork. Just mentioning it as I didn't see any mention above except for 'installing' the kit. If the extra passageways aren't there, then the rear brake is not working on all three pistons............. sorry in advance if it's been done......at least I now know about the different size M/C's recommended to make the rear hydraulic ratio better.... glad I didn't rush in 2 years ago when I thought about delinking mine :D.
 
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