Soft brake when lever squeezed slow

cbcanada

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Soft brake when lever squeezed slow

« on: June 30, 2016, 04:16:39 AM »

Hello

My brakes work very good but if I squeeze the lever very slow the lever comes all the way to the bottom to my knuckles.

This only happens when I have to stop very slow like 5 km per hour speed .

I can also duplicate the issue when I am not riding with the bike parked.. if I squeeze the lever wvery very slowly it will go down the the hand grips.

At full riding speed it's fine

The bike is s2r800 that I changed over to s2r1000 master cylinder, caliper and rotors


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Howie

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Re: Soft brake when lever squeezed slow

« Reply #1 on: June 30, 2016, 04:45:48 AM »

Sounds like the master. Find a way to isolate the master, like a fastener and seal that fits where the brake line fits. If the symptom still exists the master is bypassing internally.


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cbcanada

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Re: Soft brake when lever squeezed slow

« Reply #2 on: June 30, 2016, 12:42:07 PM »

Quote from: howie on June 30, 2016, 04:45:48 AM

Sounds like the master. Find a way to isolate the master, like a fastener and seal that fits where the brake line fits. If the symptom still exists the master is bypassing internally.

Not sure what you mean? So that the hose off the master plug it up and see if happens again? Correct?

But if it is the master why does it only happen on a slow squeeze?

I hope it's not the master, bought it off this message board from
Another member last year and just got around to putting it on..


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DarkMonster620

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Re: Soft brake when lever squeezed slow

« Reply #3 on: June 30, 2016, 01:12:47 PM »

Quote from: cbcanada on June 30, 2016, 12:42:07 PM

there might lay the issue, master was used and then dried . . seals might have rotten . . . Is it an axial or radial type? OK, coffin type or radial?


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stopintime

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Re: Soft brake when lever squeezed slow

« Reply #4 on: June 30, 2016, 01:50:29 PM »

Axial (not coffin, but black "goldline") off an S2R1000 Wink

Seal probably damaged so that it lets fluid pass when you squeeze lightly, but gets pushed into a sealing shape when squeezed hard - my guess.


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cbcanada

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Re: Soft brake when lever squeezed slow

« Reply #5 on: June 30, 2016, 05:31:26 PM »

Here is what it looks like


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Howie

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Re: Soft brake when lever squeezed slow

« Reply #6 on: June 30, 2016, 09:21:14 PM »

Quote from: cbcanada on June 30, 2016, 12:42:07 PM

Not sure what you mean? So that the hose off the master plug it up and see if happens again? Correct?

Yers.

But if it is the master why does it only happen on a slow squeeze?

Answered by stopintime.

I hope it's not the master, bought it off this message board from
Another member last year and just got around to putting it on..

This does not mean it was not working properly on the previous owner's bike.


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stopintime

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Re: Soft brake when lever squeezed slow

« Reply #7 on: July 01, 2016, 01:11:40 AM »

Brembo from Motowheels $160 You can use your clamp with mirror hole, but I don't know if it comes with a brake light switch or if your switch fits. Ask them... http://motowheels.com/c-181198-parts-brake-master-cylinders.html

From your dealer with all the parts included $266


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cbcanada

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Re: Soft brake when lever squeezed slow

« Reply #8 on: July 01, 2016, 04:49:25 AM »

Quote from: stopintime on July 01, 2016, 01:11:40 AM

So are you saying don't rebuild it and buy a new mc?


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cbcanada

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Re: Soft brake when lever squeezed slow

« Reply #9 on: July 01, 2016, 05:07:48 AM »

Ok I am now noticing a VERY slight leak of brake fluid from the master cylinder bleeder.. Could this cause the issue,, what is the best tool to tight this ? I am notorious for stripping bleeders. 😀


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ducpainter

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Re: Soft brake when lever squeezed slow

« Reply #10 on: July 01, 2016, 05:12:31 AM »

Bleeders only need to be just past snug. If you've already over tightened it and distorted the seat, the master will need to be replaced.

Put a short wrench on it and see if it moves with light pressure.


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stopintime

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Re: Soft brake when lever squeezed slow

« Reply #11 on: July 01, 2016, 07:11:21 AM »

Quote from: cbcanada on July 01, 2016, 04:49:25 AM

So are you saying don't rebuild it and buy a new mc?

I think so, since it's difficult to find rebuild kits. You could search here - it has been discussed several times. (they might be called something else)(English isn't my first language and my brain fails me sometimes)