K8 front brake problem

[jyka]

Hi

I have a problem with my gen2 K8 hayabusa front brakes;
Somehow the front brakes became weaker after a few months. After bleeding (air bubbles comes from the bleeding valve) brakes work fine - but only for a while. I have to bleed it in the every spring and nowadays even twice a summer - it seems to getting worse.
I have aftermarket brake hoses (goodridge) but it doesn't cause this because I had the same problem with the stock hoses too.
It does not leak break fluid.
I have heard the same problem from some another gen2 owners in Finland.
Any ideas what causes this? Where the air bubbles get into the brake fluid?

br, jyka

 

[cheferman65]

Could be a bad seal at the master cylinder or the reservoir. No leaking of fluid? Are you using the correct brake fluid and is it new from an unopened container? Are you seeing a loss in volume? Maybe it's the calipers?

 

[lil charlie]

If its air bubbles its a fitting not tight enough or like cheferman said. Bad master cylinder.

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[jyka]

Thanks for your answers.
I have used DOT4 brake fluid (don't remember the brand). Does it matter was it an unopened container? I can't see any fluid leaks or loss in volume.
Maybe it is a bad master cylinder :/

 

[1ibandit]

One drop of fluid is one or two air bubbles! Zero air bubbles is what you want. The question now is how to find the problem. Pump up the brakes and zip tie the lever in place. Check it and keep it tight, after a few hours you may find your leak. This works in cases of small leaks because you are applying the brakes for a long time and the problem should show up.


1ibandit
88 ZL1000, 07 KaBusa
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[lonner]

it could be the bleeders if you had it before the lines were changed as some give trouble

replace them to save going through the mc rebuild etc as there cheap and would be my guess

 

[kromdom]

Good tips above. Another one I can suggest:
1. pull in brake lever and zip tie to the grip.
2. leave on x 24 hours.
3. any and all bubbles trapped during line/fluid change, etc. should be "purged" by then.

Best of luck.

 

[jyka]

I put a rubber band to the brake lever yesterday, I just checked it and now the lever is much harder! I didn't yet check the leaks, but at least air bubbles are (partially) gone because I can't press the lever to the throttle grip any more.

 

[lonner]

I put a rubber band to the brake lever yesterday, I just checked it and now the lever is much harder! I didn't yet check the leaks, but at least air bubbles are (partially) gone because I can't press the lever to the throttle grip any more.

also turn the bars full left lock on side stand and just move the lever slightly say 5mm a few times as this bleeds the mc as air can get trapped in there and wont shift until you do as suggested and that may help.

 

[dadofthree]

I put a rubber band to the brake lever yesterday, I just checked it and now the lever is much harder! I didn't yet check the leaks, but at least air bubbles are (partially) gone because I can't press the lever to the throttle grip any more.

You probably have a small leak, if it was just air in the system I wouldn't think you could fix it and then have it repeat after time. Who knows maybe you got it. Best of luck.

 

[karnage]

Bad brake lines as well.Check fittings for sure.