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Offline dev

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Re: My brakes are very soft
« Reply #20 on: March 22, 2018, 04:12:45 PM »
Thanks everyone for contributing, great reads!

I've just talked to my mechanic, he says it's pretty weird that this would happen if there are no leaks or obvious failures.
I've pumped the brakes and tied them, they seem good now.

I'm paying close attention to them and if this happens again it's time for a serious service of everything - I don't like playing with my life :/

Offline dev

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Re: My brakes are very soft
« Reply #21 on: June 05, 2018, 09:13:34 PM »
Just to provide a quick follow up on this for anyone with similar problems in the future.
After I've tied down the brake and left if over night, tomorrow it was firm as ever.
But once I left the bike sit for a few days, it went back to being soft.

So, I decided to bleed the brakes (with a help of a friend who knows what he's doing), and we found there was air in the main caliper (obviously).
What was weird is that we found even more air in the (I'm not sure what it's called exactly) upper "chamber" - the one right next to the lever (?).
We bled that as well, although we didn't actually do 100% bleeding, we just circled the same fluid back in (it's new anyway).
Then after 2 weeks of not riding, the breaks were soft again, but this time a bit better. We repeated the same procedure again,
and they seem quite fine now. They are somewhat softer again after not riding, but almost not noticeable - I believe we removed all air now, maybe we'll do another run just to make sure. I hope it won't happen again because I couldn't explain what was causing it.
Will update if there's any new development.

Thanks everyone for the advice!

Offline whyhaveone

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Re: My brakes are very soft
« Reply #22 on: June 06, 2018, 12:55:55 AM »
Thanks for letting us know.  :028:
Kawasaki: 1975 250-S1C; 1977 Z650-B1; 1980 Z1000 MKII A3; 2010 ER6n; 2013 Z1000SX ABS; 2016 Z1000SX ABS Tourer

Offline dev

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Re: My brakes are very soft
« Reply #23 on: November 21, 2018, 03:46:36 PM »
Ok, I just now got around to posting an update here, as I'm not riding much this season :(

The problem is back. We changed the brake oil, and the brakes were great, very firm.
After I left my bike in the garage for a few weeks, I returned to find the brakes again fully soft, I could easily touch the handle with them :(

So it seems I haven't resolved the problem - what could it possibly be?? There are no faulty brake lines, and there is no oil leaking anywhere.

Could it be that the Master Cylinder is letting in air? How would that even be without letting the oil out?
Should I get a Master Cylinder Repair Kit? I'm lost.


Offline sc00bie

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Re: My brakes are very soft
« Reply #24 on: November 21, 2018, 08:44:27 PM »
Hi,
Sorry not read through all the post... horrible tracing slow pressure loss!

Its possible for the master cylinder seal to be allowing air in
Its also possible for air to get in at any of the brake line connections.
Have you also checked the flexi hoses for cracking/perishing/damage especially at the working bends and the rubber hose to metal banjo connectors
There is also the piston seals in the caliper's, so I would check there is no sign of any fluid misting there.
Has there been any history of accident damage to the bike?
Checking the banjo bolts for tightness (each fixed bolted connection) or simply replace the copper washers, ensuring the surfaces between each face is clean and no pitting/high spots, torque off the banjo's, re-bleed brakes and test

Process of elimination suggestion

Clamp of one side of the brakes nearest to the splitter for the R/L sides, you must ensure that the clamped side not under testing does not allow fluid movement.
For clamping off the flexi hoses and no proper hose clamp I use a pair of long nose mole grips, putting something between flexi and mole grips and just enough pressure to close of the hose. A bit Heath Robinson but …. Alt buy a brake hose clamp and be safe avoiding any damage to the hose.

DO the pressure test and check for softening of the brake after a reasonable period of time day /2 day's etc

If there is no loss of brake pressure then that side is good.

If there is pressure loss then clamping the flexi nearest to the caliper – test – check -
All Ok move clamp nearer to m/cyl or next brake hose - re-test.

Do this as far as you can go with the one side until you reduce the distance between m/cyl and clamp point.
Determine if it could be banjo bolt connections or m/cyl or if lower down between the clamp point and last non clamped section.
If its e.g happening without anything on the one side clamped, clamping the hose nearest to the caliper will highlight caliper or connections, some calipers are a 2 piece affair and I have seen leaks between the faces of the 2 sides due to corrosion.

If no loss of pressure at all then clamp this side off nearest to the splitter for the R/L sides and repeat on the opposite side
The idea is to rule out where the air is being drawn in or if indeed there is a leak.

I have come across worn brake lever cam, this is the point where it meets the master cylinder and compresses the piston forcing the fluid to move in the hoses, although this was on a bike in the 1980/90's the interaction of the brake levers may have changed since, but thought it would be worth mentioning. Because the lever is under tension the cam wears flat reducing the pressure exerted on the m/cyl and therefore loss of brake pressure.

Also possible for the hoses to expand if they are getting on in years again causing the pressure to drop but may not be showing any signs of leakage.

I hope this might help and you find the problem.
good luck
Sc00bie

Offline dev

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Re: My brakes are very soft
« Reply #25 on: November 22, 2018, 09:56:21 AM »
*Originally Posted by sc00bie [+]
Hi,
Sorry not read through all the post... horrible tracing slow pressure loss!
...
I hope this might help and you find the problem.
good luck


Hi sc00bie, thank you very much for the long and helpful post! I admit that I'm new to the terminology (and English is not my native language), so I will have to spend some time with Google to understand what all the parts you mention actually are :)

But to be on the safe side, would you say I can account for most of this work by completely replacing the brake lines (they are 7 years old and I might just go for it, even take the braided ones), and rebuilding the master cylinder (the rebuild kit is not that expensive, around 50€). Would that be better than trying to clamp and test as you described?

Thanks again!

Offline sc00bie

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Re: My brakes are very soft
« Reply #26 on: November 22, 2018, 10:50:53 AM »
Hi Dev,

if you do the brake lines and master cylinder, the only things you wil not have tested is the brake calipers.

Braided hoses should also improve the brake feel.

What you suggest and if its within your budget will take care of 90% of the brakes on the front.

Try to bleed one side at a time and make sure there is 100% no air in the brake lines. When rebuilding the master cylinder lubricate seals with clean brake fluid.

I would still still fully pressure test when you have replaced all the hoses, copper washers etc and make sure there is no loss.

best wishes
Sc00bie

Offline burty

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Re: My brakes are very soft
« Reply #27 on: November 22, 2018, 05:21:26 PM »
Don't replace the brake lines before replacing the seals in the calipers first.  My money is on this bring the source of the problem.

That said, if they are 7 years old, the replacement of the brake lines is well overdue.
2017 Z1000SX, in black.  Roughly 70000 miles and 8 years on SXs.

Offline sc00bie

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Re: My brakes are very soft
« Reply #28 on: November 22, 2018, 06:37:58 PM »
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...
Sc00bie

Offline dev

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Re: My brakes are very soft
« Reply #29 on: November 23, 2018, 09:11:04 AM »
Wouldn't the caliper seals leaking mean oil getting out? At least that's how I imagine it. But there's no oil leakage AT ALL!

p.s. my English is quite good actually, it's just the new terminology around this topic that I need to catch up on, so feel free to type away as you would normally :)