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Discussion Starter #1
During my last 2 test rides on the bikes the front brakes have seized up to the point the bike is unrideable.

If I open the caliper bleeder I can ride it home but from what I can tell it sounds like the brake pads might be dragging a little? From what I've read it could explain why the brakes start out OK but then get tighter and tighter until they lock.

How do I go about fixing this issue? Getting a little nervous each time I take this thing out. I've bled the lines (front left, front right, master) and the brake fluid is just below full.
 

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Any chance you ( or someone ) replaced the front brake lever?

It sounds as if there is not enough bleed down on the master cylinder and the fluid cannot return when you release the lever. Cheap levers often place the pin holes in the wrong spot so the hydraulics do not function the same. If you are running a oem Brembo lever look for the fluid to be able to return to the reservoir by prying the pads back with the cap off (watch for paint damage, flush with water if you get any on the paint. )
 

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Discussion Starter #3
Any chance you ( or someone ) replaced the front brake lever?

It sounds as if there is not enough bleed down on the master cylinder and the fluid cannot return when you release the lever. Cheap levers often place the pin holes in the wrong spot so the hydraulics do not function the same. If you are running a oem Brembo lever look for the fluid to be able to return to the reservoir by prying the pads back with the cap off (watch for paint damage, flush with water if you get any on the paint. )

What do you mean by prying the pads back? Like take the calipers off and push them back in? It's a stock OEM brembo front brake lever.
 

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Unbolt the caliper and with a slight twisting motion of something flat between the pads you should be able to push the caliper pistons back into the calipers. Careful not to damage the pads it should not take much force so pad damage should not be an issue. Any chance the reservoir is over filled?

There are cheap Chinese knock off levers out there so verify the lever is truly Brembo. hint: oem brembo will usually have a manufacturers date calendar on both the outer lever and the pivot piece. look on the underside for these circular calendars.
 

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The issue is most likely the pointy thing on the lever that contacts the master cylinder. See picture.

It need to be backed out a half turn or more. My guess is that right now it is applying minute pressure to the master cylinder causing the brakes to lightly engage. With the brakes continuously engaged the brake fluid heats up and expands causing the brake to eventually lock up.
 

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Discussion Starter #6
And how do I back out that little do-dad?

The issue is most likely the pointy thing on the lever that contacts the master cylinder. See picture.

It need to be backed out a half turn or more. My guess is that right now it is applying minute pressure to the master cylinder causing the brakes to lightly engage. With the brakes continuously engaged the brake fluid heats up and expands causing the brake to eventually lock up.
 

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The return port in the master cylinder is either partially plugged or partially covered by a misadjusted MC piston travel. It can't allow the quickly heated fluid to expand back to the reservoir.

https://commons.wikimedia.org/w/index.php?curid=24878290

This is from an earlier post. Apologies to the original poster for failing to credit him — lost the info.
 

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The Brembo brake pin is NOT adjustable for length it is just set in the drum. there is no reason to need to adjust it and I am sure that Brembo made it non-adjustable for liability reasons. That does not mean the issue is not related. If something gets between the pin and its stop you will have the same effect (lack of return) so making sure that there is not something there is worth doing. There also is a spring in the master under the rubber boot that I have seen get between the pin and master cylinder piston giving the same issue. this was a on a often crashed bike so there should be less chance of you having this happen.
 

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Discussion Starter #9
Thanks, so if I take this off I should be able to disassemble it, put it back together and that may fix the issue? And if not I'll then try the calipers themselves. The bike sat for 2 years so it wouldnt be nuts to think the MC is clogged.

The Brembo brake pin is NOT adjustable for length it is just set in the drum. there is no reason to need to adjust it and I am sure that Brembo made it non-adjustable for liability reasons. That does not mean the issue is not related. If something gets between the pin and its stop you will have the same effect (lack of return) so making sure that there is not something there is worth doing. There also is a spring in the master under the rubber boot that I have seen get between the pin and master cylinder piston giving the same issue. this was a on a often crashed bike so there should be less chance of you having this happen.
 

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swear at it a lot. really go to town. threaten to smash the living shit out of it.

then just spend an hour losing your mind trying to get it back in. be gentle. take out your anger on an old oil drum with an old fork leg. or maybe a 24" breaker bar if you have one of them. i have a really nice snap on one.
 

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Discussion Starter #11
Lol deleted to save the embarrassment, used some needle nose pliers to open it up.

swear at it a lot. really go to town. threaten to smash the living shit out of it.

then just spend an hour losing your mind trying to get it back in. be gentle. take out your anger on an old oil drum with an old fork leg. or maybe a 24" breaker bar if you have one of them. i have a really nice snap on one.
 

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One thing often overlooked is the vent in the fluid cap could be blocked.
This allows pressure from the heated [expanded] brake fluid to apply the brakes because there is nowhere for the air on top of that rubber seal in the cap to go. Try loosening the cap when the brakes are dragging and see if they free up.
 

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Discussion Starter #13
One thing often overlooked is the vent in the fluid cap could be blocked.
This allows pressure from the heated [expanded] brake fluid to apply the brakes because there is nowhere for the air on top of that rubber seal in the cap to go. Try loosening the cap when the brakes are dragging and see if they free up.
It's definitely the caliper pistons, or so it seems. Took the calipers apart last night (in half) and pressed in the pistons. Reassembled, bled, and then zip tied the front brake overnight. This morning same issue, the pistons don't release (drag).

So here's my new question. From the YouTube videos I've seen they all say replace the piston seals. But this is an 18 year old bike and the brakes have only 7k miles so can I get away with reusing the piston seals?

I'll pump out the pistons, steel wool them, wipe down with brake fluid, use brake cleaner inside both calipers and reassemble them. Sound like a good start? I don't think I need to replace the pistons.
 

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Discussion Starter #15 (Edited)
are you using anything to lube the seals-bores besides brake fluid?
https://www.amazon.com/Raybestos-BA...rd_wg=gxWhF&psc=1&refRID=DYXEATFJRVQPBBZEB81V I installed this kit last year with assembly fluid-solved the drag.
https://www.ebay.co.uk/itm/Ducati-9...505573?hash=item2a302741e5:g:bFsAAOxymnFSC2Tt
Had not see that product mentioned, just to use brake fluid to lubricate, so thanks! Are new seals a necessity? Since I'm itching to ride and these parts are coming from the UK ?
 

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The seals are 18 years old, and the brakes are giving you trouble. The miles are mostly irrelevant.
I think you answered your own question.

Spend the few bucks, wait the short time necessary, do it right and you won't have that nagging voice in the back of your head, wondering when it will come back....
 

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Do you have free play in the lever?

The master cylinder piston is adjusted at the factory so that, in its fully retracted state/starting position, the fluid return port to the reservoir is completely uncovered.

Essentially, until the piston moves far enough to cover the port, fluid can flow from the cylinder to the reservoir and thus the fluid is not pressurized sufficiently to cause the lever to generate the forces required for brake actuation (or clutch engagement)
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Properly adjusted, there should be a 5-10% dead-band of the full lever movement before there is pull resistance felt at the lever. This free play is necessary to prevent covering the port as the piston seal expands normally over time, and to avoid placing the piston seal rest location (where corrosion occurs) right at the return port orifice.

Once adjusted, the manufacturer places a potting compound over the screw adjuster to prevent accidental or incorrect adjustment.

If the potting compound is removed and the piston is incorrectly adjusted such that the return (compensating) port is completely or partially blocked when the lever is released, the system will remain partially pressurized for a time, and the clutch engagement will be incomplete, causing slippage and premature wear. Similarly, the same mis-adjustment of the brake master cylinder leads to BRAKE LOCK-UP when the brake fluid heats up.

Sometimes corrosion or contaminated fluid will plug the fluid return port causing the same problems.

It’s been suggested here that you can do this adjustment yourself by checking for a squirt of fluid into the reservoir when you initially pull the lever, i.e., if you can see a squirt, it’s OK. However, keep in mind that you’ll still see a squirt with a partially blocked port.
 

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Gotham cycle has the rebuild parts....located in florida
 

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Discussion Starter #19
Bought and installed the new seals. After purging the lines, it seems they are still sticking in the engaged position. The pistons and original seals were in great shape, used 000 steel wool to clean the pistons of some old grime. What's my next step if the pistons aren't receding?
 

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brake hoses?

a collapsed inner liner can keep fluid from returning to the master.how much force is needed to push the pads apart-pistons back into the calipers with the master cyl. cap loose and a rag to prevent spills handy? should be close to the same pressure for all 4.
 
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