do I need a new brake master cylinder? [update]

[martin_14]

back to this.
After around 400 miles with the brand new brake master cylinder, the same behaviour developed. The free play on first application of the front brakes is too much, after quick release and reapplication of the lever, it goes to normal.
So I took the bike back to the dealer as well as the "old" brake master cylinder to be reinstalled. The dealer's owner was disappointed and asked me to leave the bike at his place for the winter, so he could investigate the issue more thoroughly. He's not happy with not being able to sort this out for me. And since the bike is unregistered during the winter, it's irrelevant to me where it hibernates.
So, I'll leave this post sleeping until the beginning of March, when I'll pick up the bike and see if there's anything improved.
Meanwhile, if any of you guys has any suggestion, I'm all ears.

[lather]

<SNIP>
So, I'll leave this post sleeping until the beginning of March, when I'll pick up the bike and see if there's anything improved.
Meanwhile, if any of you guys has any suggestion, I'm all ears.

I don't feel like reading through the whole thread to see if this has been covered before, so if it has I beg pardon. I believe warped rotor or wheel offset in the forks could cause this behavior. Obviously (I think) a warped rotor would be noticeable in the bars on braking so apparently not warped. But the wheel offset may not be noticeable except as what you are describing. By wheel offset I mean the wheel not centered between the forks. I suspect the mechanics who have looked at it have checked for this but maybe not. Good luck.

[PlaynInPeoria]

That's a good point.  A warped rotor would push the pads out, which would mean that when you grabbed the brakes, they would feel soft initially because they are touching nothing, then would stiffen up when they came in contact with the discs. 

Good potential diagnosis there.

Ahh, after rereading, it was offered as a potential cause.

[PlaynInPeoria]

I have a question, Martin.  I read the entire post and didn't see much about it.

Have others you trust ridden the bike when it is exhibiting the symptom/problem and confirmed that they feel it too?  Not trying to be offensive but you are part of the system also and it seems most everything else has been changed (master cylinder, lines, pads, fluids).

[martin_14]

@lather: yeap, one disc was warped by 0.4mm. Kawasaki indicates that 0.3mm is the maximum allowed, so I changed the disc. No good. Now both discs are at 0.08 and 0.12, which are good values.

@PlaynInPeoria: yes, friends drove the bike, and noticed the same. 2 mechanics at the dealer, too. And I drove other bikes (20 or so, mostly BMWs but Hondas, Kawasakis and one Suzuki too) and none of them exhibited this issue. Hell, I drove the new J300 scooter from Kawasaki (which is a freaking Kymco) and it has a much better feel to it.

[PlaynInPeoria]

That sucks, man.  Good luck and keep us posted.

[flashback50]

I'm just wondering if this problem might be linked to the ABS pump. One of the complaints I read about the front brakes on the other forum, was that they went mushy and it ended up being an ABS pump. Just a thought.

http://forum.cog-online.org/say-anything-here-except-that!/maintenance-or-lack-there-of/

[martin_14]

well, the issue has been solved. After replacing the brake lines by SS lines, disconnecting the ABS unit and driving around a few days, changing the brake pump, bleeding the lines, and redoing callipers and master cylinders, I decided to go bold and just change the callipers. My dealer, Kawasaki Europe and I figured that if there was something wrong with the callipers, and they were retracting the pistons too much, that could explain behaviour. So I sourced both front brake callipers from a salvage yard and had them mounted, and voilà, brakes run perfectly for the 1000 miles that I had the bike until I was run by a bus.
So... short lived good news 
Case closed.

[gPink]

You going to salvage the salvage calipers?

[VirginiaJim]

well, the issue has been solved. After replacing the brake lines by SS lines, disconnecting the ABS unit and driving around a few days, changing the brake pump, bleeding the lines, and redoing callipers and master cylinders, I decided to go bold and just change the callipers. My dealer, Kawasaki Europe and I figured that if there was something wrong with the callipers, and they were retracting the pistons too much, that could explain behaviour. So I sourced both front brake callipers from a salvage yard and had them mounted, and voilà, brakes run perfectly for the 1000 miles that I had the bike until I was run by a bus.
So... short lived good news 
Case closed.

In more ways, than one.

[martin_14]

You going to salvage the salvage calipers?

They got scratched in the mishap, so I'm not sure.