Brembo 19X20 master cylinder question - Honda RC51 Forum : RC51 Motorcycle Forums
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post #1 of 16 (permalink) Old 04-10-2019, 07:35 PM Thread Starter
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Brembo 19X20 master cylinder question

Okay, question for all you Brembo brake experts.....

I am rocking the forged 19X20 master cylinder on my RC and it is a few years old now. I have always noticed that the lever travel seems to be a little much before I can feel the break fluid start to engage. I'm probably talking like 1 1/2 inches before there is any activation. I used to have the Brembo cast master cylinder and it had maybe 1/2 inch of travel or less. Is this normal?
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post #2 of 16 (permalink) Old 04-10-2019, 07:57 PM
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that is brutal. the 19x20 should have pretty well no travel at all before biting (it's got the most plunger travel per lever travel, basically the least leverage, but tightest lever)


my setup with a 19x18 has maybe 1/4" of free travel before it's firm. yours should be even tighter than that.




try bleeding at the master first, once the master is clear bleed at the calipers.


leave it overnight, then bleed at the master again. the highest point in the system is the bleed nipple, so any air will collect there.
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post #3 of 16 (permalink) Old 04-10-2019, 09:02 PM Thread Starter
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Yeah. I have bled everything over the years, installed new brake lines, rebuilt the calipers and there has always been a lot of lever travel. I thought it was just that way. But after thinking about it, it should not be that way. It does not leak. I guess there are internal seals that would need to be changed by a “certified Brembo tech”. It has all of the original components.
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post #4 of 16 (permalink) Old 04-10-2019, 09:47 PM
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nah, it's a very simple rebuild.. just a some lip seals on the plunger. it all comes apart very easily with a pair of snap ring pliers.


does it hold pressure though? ie if you pump it up and tie it to the bar does it keep its pressure?
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post #5 of 16 (permalink) Old 04-10-2019, 09:50 PM Thread Starter
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It keeps pressure and has a fairly solid feel.
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post #6 of 16 (permalink) Old 04-10-2019, 09:58 PM
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interesting. is the plunger retainer still in good condition? you may have a bunch of deadband from a damaged retainer.



basically the plunger is retained by a ring. the actuator pin has a ball end and goes through the ring.


if you remove the lever you'll see there's a snap ring holding the retainer in place. if you remove the snap ring the retainer will come out and the piston will follow it.


if the actuator pin is well worn, it would allow the piston to come back further in the assembly, which would add deadband (basically the travel of the piston during which the port to the reservoir is still in front of it)



if it were me i'd pull the lever and the plunger retainer and make sure that all those parts are in good condition. if the'yre well worn you can replace them with a simple rebuild kit. the actuator pin tends to fail in crashes where the lever is subject to pulling force. it tends to rip out the pin and retainer.
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post #7 of 16 (permalink) Old 04-12-2019, 04:11 PM
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Throw that old shit away and buy a new RCS 19

I mean it's not like the brakes are really that important or anything...
Motleyfan and Adbanshee like this.
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post #8 of 16 (permalink) Old 04-12-2019, 04:15 PM
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I just went out and looked I have a drawer full of the old school Forged MkII 19X20 Brembo Masters brand new. You can have one cheap!
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post #9 of 16 (permalink) Old 04-12-2019, 08:57 PM Thread Starter
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Hey Mike I will be in your neighborhood on Wednesday and stop in and maybe take one off your hands.
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post #10 of 16 (permalink) Old 04-14-2019, 11:05 AM
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Right on good sir!
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