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Offline NorfolkNinja

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Re: My brakes are very soft
« Reply #30 on: November 23, 2018, 09:46:30 AM »
This might help.
My mate rides a 2012 Diavel and no matter what a service technician did he couldn't get rid of sponginess (to my mates satisfaction) to the point he could almost get the lever back to the grip when pulled really hard. When riding he would have to pull the lever twice to get rid of the initial sponginess. When investigating on the forums he found 'they all do that' and even checking new ones in a showroom weren't much better. On the point of giving up and selling on the technician suggested a racing Brembo master cylinder, the difference is night and day and a magic fix but cost him £250.
He mentioned this to tech at the bike show yesterday and they are aware of the problem and suggested using Motul brake fluid.
Maybe using a sledgehammer to crack a walnut but my mate is one happy bunny now.
https://www.bikehps.com/acatalog/Brembo_Radial_Front_Brake___Clutch_Master_Cylinder.html?gclid=EAIaIQobChMIxcHh55rq3gIVy7_tCh0mrQ6-EAQYASABEgLgTPD_BwE#a51079

Offline sc00bie

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Re: My brakes are very soft
« Reply #31 on: November 23, 2018, 03:41:20 PM »
Dev - thanks, yes there would be signs of leakage, dampness.

NorfolkNinja - I'll keep that in mind  :028:

I lnoe moving brake fluid from dot 4 to 5 can also improve feel.
I'm hedging its brake hoses expanding with age or wesr in master cyl...
Sc00bie
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Offline burty

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Re: My brakes are very soft
« Reply #32 on: November 23, 2018, 08:19:04 PM »
*Originally Posted by sc00bie [+]
Burly, good to hear if you have experience of the seals leaking.
Hence tbe pressure testing I suggested.

What drives your piston seals replacement advice?

Dev is not local and looks like he needs to translate what we write...

My rationale is that seals within the brake calipers can cause very similar symptoms.  I've experienced this on the zrx that I had a few years ago.   

Essentially there are three causes of this type of problem:. Air in the system.  Too much give in the system.  Or flex in the rubber components. It's likely that air can get in at either master cylinder or brake caliper without any obvious leaks.  It's possible to have leaks a brake hose joints but this normally comes with an indication of weeping. 
Personally,  I would check how well worn the pads are and change them if they are well worn.  I would change caliper seals, then master cylinder internal rubber components, then brake hoses.  All of these will make a difference as they are 7 years old anyway.
2011 Z1000SX, in GREEN, owned since September 2011.  50,000 miles, MCT tweaked front suspension, Maxton Rear shock, heated grips, MRA dark sport screen, PDoiler, Scorpion Serket Exhausts.

Offline sc00bie

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Re: My brakes are very soft
« Reply #33 on: November 24, 2018, 05:48:23 PM »
thanks burty, I'm a mechanic to trade so wondering if there were specific issues on certain manufacturers,

Been mostly brake hoses that have been issue Ive seen in my limited time with bikes, cars .... well different beasties

cheers
Sc00bie
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Offline dev

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Re: My brakes are very soft
« Reply #34 on: November 26, 2018, 11:38:34 AM »
*Originally Posted by NorfolkNinja [+]
This might help.
My mate rides a 2012 Diavel and no matter what a service technician did he couldn't get rid of sponginess (to my mates satisfaction) to the point he could almost get the lever back to the grip when pulled really hard. When riding he would have to pull the lever twice to get rid of the initial sponginess. When investigating on the forums he found 'they all do that' and even checking new ones in a showroom weren't much better. On the point of giving up and selling on the technician suggested a racing Brembo master cylinder, the difference is night and day and a magic fix but cost him £250.
He mentioned this to tech at the bike show yesterday and they are aware of the problem and suggested using Motul brake fluid.
Maybe using a sledgehammer to crack a walnut but my mate is one happy bunny now.
https://www.bikehps.com/acatalog/Brembo_Radial_Front_Brake___Clutch_Master_Cylinder.html?gclid=EAIaIQobChMIxcHh55rq3gIVy7_tCh0mrQ6-EAQYASABEgLgTPD_BwE#a51079

Thanks for the answer! But I don't think my problem is similar, because my breaks are great after I bleed them, and as long as I ride regularly they keep like that for weeks. The problem I notice is when I don't ride for a few weeks, they degrade quickly and become very soft (I can't even break with 100% before hitting the handle, so I have to pump them previously, or tie them overnight to get some air out).

*Originally Posted by sc00bie [+]
Dev - thanks, yes there would be signs of leakage, dampness.

NorfolkNinja - I'll keep that in mind  :028:

I lnoe moving brake fluid from dot 4 to 5 can also improve feel.
I'm hedging its brake hoses expanding with age or wesr in master cyl...

There is no leakage of oil anywhere, nor is anything damp...
Also, the brake hoses expanding with age or whatever is not consistent, because everything works great after bleeding, and then becomes soft as the bike sits for a few weeks. So it's definitely something happening over time, like air getting in somehow.

*Originally Posted by burty [+]
My rationale is that seals within the brake calipers can cause very similar symptoms.  I've experienced this on the zrx that I had a few years ago.   

Essentially there are three causes of this type of problem:. Air in the system.  Too much give in the system.  Or flex in the rubber components. It's likely that air can get in at either master cylinder or brake caliper without any obvious leaks.  It's possible to have leaks a brake hose joints but this normally comes with an indication of weeping. 
Personally,  I would check how well worn the pads are and change them if they are well worn.  I would change caliper seals, then master cylinder internal rubber components, then brake hoses.  All of these will make a difference as they are 7 years old anyway.

Thanks for the answer, this one seems right on point - since my brakes are doing well after bleeding them,  and degrade after a while, seems to point air coming into the system somehow, not so much that the hoses are stretching due to age, etc.
About brake pads: that would make sense if the softness is permanent, but it's not - if I bleed them, they are good for a while. I will check the pads anyway though.
My concern about the caliper seals is this: how can air get inside a pressurized system, without oil getting out ever?
So it has to be master cylinder? Or does the same apply there? I can't really make sense of it all because I don't have any experience with brake systems :|

By the way, I just checked and OEM Kawasaki hoses are ~420€ JUST FOR THE FRONT END! Oh man, I wasn't expecting it to be that expensive :/ are there good quality solutions from other manufacturers which would be cheaper and widely used perhaps? :D

Offline maccmike

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Re: My brakes are very soft
« Reply #35 on: November 26, 2018, 12:20:38 PM »
Definitely don't go for oem hoses. Braided pipes from HEL or Goodrich are much better quality and give far better feel as well as being much cheaper. For instance on link below £95 for full kit for non abs bike.

https://www.helperformance.com/kawasaki-z1000sx-2011-2015

Offline dev

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Re: My brakes are very soft
« Reply #36 on: November 26, 2018, 12:39:22 PM »
That's extremely helpful, thank you very much!
And wow, what a price difference. My bike has ABS, so that's £159.99, which is still just 40% of the OEM price :D

So to summarize and get your guys blessing for further actions:
- check for mist around calyper seals
- test hoses as sc00bie suggested, or just replace them entirely with a braided version (thanks maccmike)
- rebuild the master cylinder with one of these kits (still have no idea how to do that, but I'll learn as I go)

Does that sound right? I would do each step and evaluate results afterwards. Is this the order you would recommend?
Is there something else I'm missing?


Offline maccmike

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Re: My brakes are very soft
« Reply #37 on: November 26, 2018, 12:52:08 PM »
I have these on my SX, really good quality & only £125 for the full ABS set.

https://wezmoto.com/product/kawasaki-z1000-sx-abs-2011-2015-oem-standard-layout/

Offline dev

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Re: My brakes are very soft
« Reply #38 on: November 26, 2018, 02:34:53 PM »
*Originally Posted by maccmike [+]
I have these on my SX, really good quality & only £125 for the full ABS set.

https://wezmoto.com/product/kawasaki-z1000-sx-abs-2011-2015-oem-standard-layout/

Excelent! Thank you maccmike! :)

 


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