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Discussion Starter · #1 ·
I've been having problems with my front brake lever getting a little squishy. It is still a firm lever pull, but when I get to the end of the travel it used to feel like the lever hit a brick wall and just stopped. Now it feels like I can keep squishing it before it finally stops. It doesn't pull all the way to the bar or anything like that, and the brakes still work pretty good, but not as good as I'm used to.

First time it happened was a few months after I changed the pads and bled the system, so whatever, I bled it out and found there was air in the master cylinder. The lever got firm and I was happy again, a few hundred miles later, it went back to squish. So I bled the system again and again found air in the master. This time though the lever was still squishy. A few days later I bled again and found more air in the master. Got all the air out and again, but right away I got squish in the lever.

I checked the banjos and they're all tight, the bleeder valves aren't loose and I don't see any leaks or fluid loss in the reservoir. But somehow air keeps getting into the master. I'm wondering if the master cylinder maybe are just gone bad? It's a $170 part though so I want to try everything I can first.

It's a full Brembo system with stainless steel braided lines. But the bike is over 5 years old, but only about 12000 miles on it. I just got it about a year ago. I tried different brands of fluid, Motul, Bel Ray, and Galfer, but still I'm getting air in the master. I've also tried putting a tie wrap around the lever to hold the brake on after bleeding to let the air bubbles float up to the reservoir but that's not working either.

Any ideas for anything else I can try before buying a new master? Thanks guys.

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I would try lots of things before I bought another MC!

Lessee - So the tie wrap around the lever doesn't "let the air bubbles float up to the reservoir". They would float upward if given a chance anyway, and having the brake on actually *prevents* them from entering the reservoir. It is, however, a good way to pressure-test your system. If you leave the lever pulled overnight, and it doesn't come back to the bar, then you aren't losing line pressure anywhere.

The places I would look first, given your symptoms, are the caliper piston seals. Those need to be replaced every so often anyway, and are much more likely to get nicked in such a way as to let air in when the pads retract.

Why do you feel the air in the system is at the MC? Just because it comes out there doesn't mean much - that's a common sticking location for air anywhere in the system as it migrates upwards.

KeS
 

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Discussion Starter · #3 ·
Whenever I bleed I'm not getting air out of the bleeder valves on the calipers, but every time I am getting air bubbles out of the bleeder valve on the master.

Can I just visually inspect the piston seals by pulling the caliper and pads, or do I need to disassemble the caliper?

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I would replace the mc. Brakes are pretty important. Or take it to the dealership if you can not figure it out and get it fixed right.
 

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You gotta take the caliper apart .. and if yer going to do that you should just change the seals as a matter of course .. the other option for parts worn is the sealing oring in the caliper where it splits at the fluid way . Make sure when you get piston seals you also get the orings for rejoining the calipers .
 

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I had the same problem on my R6 and never figured it out. No leaking fluid or anything. I would bleed the brakes before every track day and that helped for a short time but by the end of the day the lever would be squishy again.
 

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Can you "pump" the lever and get them back up firm without bleeding? I had my bike fall over in the trailer, and I tweaked a front rotor ever-so slightly. I couldn't find it with measuring calipers or a straight-edge. I centered a laser on the rotor edge and could barely see a very slight "wobble" in it when I spun the wheel. The rotor was only warped enough to make the lever get squishy over time/miles when I rode it
 

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Discussion Starter · #8 ·
Can you "pump" the lever and get them back up firm without bleeding? I had my bike fall over in the trailer, and I tweaked a front rotor ever-so slightly. I couldn't find it with measuring calipers or a straight-edge. I centered a laser on the rotor edge and could barely see a very slight "wobble" in it when I spun the wheel. The rotor was only warped enough to make the lever get squishy over time/miles when I rode it
No, I can't even get them back to how they used to be with bleeding, while pumping the brakes the feel stays consistent though.

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Discussion Starter · #9 ·
So turns out Brembo does not sell rebuild kits or individual seals/o-rings for any of their calipers or master cylinders, too many problems and lawsuits with people messing them up I guess. So my only options are $170 for a new master or $300 each for a new caliper.
 

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Or find the appropriate cross reference parts.

Trust me, Brembo sells them. A little research will fix you right up
 

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Or find the appropriate cross reference parts.

Trust me, Brembo sells them. A little research will fix you right up
+1

Rebuild kits are definitely out there

Try contacting HardRacing or OPP Racing
 

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So turns out Brembo does not sell rebuild kits or individual seals/o-rings for any of their calipers or master cylinders, too many problems and lawsuits with people messing them up I guess. So my only options are $170 for a new master or $300 each for a new caliper.

Brembo Goldline Single Caliper Seal Kit. Ducati 600 Aprilia Pegaso Tuono KTM | eBay

Well that took me 2 seconds .. And in another 5 mins I found KTM europe supply them And so does Aprilia Europe .
 

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Discussion Starter · #13 ·
Brembo Goldline Single Caliper Seal Kit. Ducati 600 Aprilia Pegaso Tuono KTM | eBay

Well that took me 2 seconds .. And in another 5 mins I found KTM europe supply them And so does Aprilia Europe .
Thanks, I want sure those were the same calipers as those aren't radial mount, but after a little research I found they are the same thing.

Turns out I didn't need anything though. I pulled the calipers off to look at the seals and actuated the pistons a few times by hand in and out. After that was done I had a super firm lever and it's lasted a week now. Looks like there may have just been an air pocket trapped somewhere inside the caliper that wasn't moving with normal bleeding. But by moving the pistons in and out I must have pushed it up to the reservoir.

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Thanks, I want sure those were the same calipers as those aren't radial mount, but after a little research I found they are the same thing.

Turns out I didn't need anything though. I pulled the calipers off to look at the seals and actuated the pistons a few times by hand in and out. After that was done I had a super firm lever and it's lasted a week now. Looks like there may have just been an air pocket trapped somewhere inside the caliper that wasn't moving with normal bleeding. But by moving the pistons in and out I must have pushed it up to the reservoir.

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Why do you feel the air in the system is at the MC? Just because it comes out there doesn't mean much - that's a common sticking location for air anywhere in the system as it migrates upwards.
:thankya

:cheers

KeS
 

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Discussion Starter · #15 ·
Well, a week later and it happened again, getting quite frustrated now, maybe I'll try doing the rebuild...
 
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