Front brake problem

[craig mac]

Hi all,
got a problem with the front brakes, hope you can help.
recently I have replaced the seals in the front calipers, pulled the master cylinder apart and cleaned it up. didn't replace the brake pads they looked ok.
i reassembled the whole lot changed the brake fluid, bled the system thoroughly (I think) (checked it 3 times). have adjusted the brake lever so it sits furthest from the throttle. the lever feels spongy and is quite long. it will pull up about 10 mm from the throttle. the bike will stop but does not feel right at all. there are no fluid leaks anywhere. i cable tied the brake lever over night. when I released it the lever felt perfect, then later that day after no use the lever was long and spongy again. rebled, recable tied, exactly the same thing. any ideas would be great before i take it to a mechanic. cheers

[robracer]

Did you put a new kit in the MC?

[Blurr]

Might be a slow air leak in the MC seals.

[Jonno]

What year 9R and are the lines the originals?

Is it spongy then holds pressure or eventually leaks down until the lever hits the bars?

Bleed it again (I use a self bleed kit $5 supacheep).

Reason that cable tieing works is it temporarily expands the rubber braided lines to the max, so when you go to use the brakes next it is already expanded and taking less lever to activate the brake caliper pistons. The other theory is it helps air bubbles rise to the master cyl under pressure.

In any case if this is on your 9R I would say get braided lines if they are still original as this may be one part of the issue that they are old and stressed, the other would to use the self bleeding kit and keep flushing it through for quite a while (I have used nearly 300ml to be sure)

HTH

[Sulli]

you should bleed it at the master cylinder first generally by cracking the banjo and ensure the master cylinder is set up level to pump out all the air

[craig mac]

Did you put a new kit in the MC?

no new kit. i inspected the piston it looked good , no pitting etc... and the rubber seal looked ok, but thinking about it now the seal did seem quite hard. your right rob, a good place to start. which parts should i replace in the MC?

Might be a slow air leak in the MC seals.

should i only be worried about the seal that sits at the end of the piston ? the seal that sits immediately under the MC cover is just for stopping reservoir leaks right?

What year 9R and are the lines the originals?

Is it spongy then holds pressure or eventually leaks down until the lever hits the bars?

Bleed it again (I use a self bleed kit $5 supacheep).

Reason that cable tieing works is it temporarily expands the rubber braided lines to the max, so when you go to use the brakes next it is already expanded and taking less lever to activate the brake caliper pistons. The other theory is it helps air bubbles rise to the master cyl under pressure.

In any case if this is on your 9R I would say get braided lines if they are still original as this may be one part of the issue that they are old and stressed, the other would to use the self bleeding kit and keep flushing it through for quite a while (I have used nearly 300ml to be sure)

HTH

it's a B4 model (12/96) 6 pot calipers. brake lines original.
yeah, spongy then holds pressure.
i will go and check out the self bleed kit.
i never thought about replacing brake lines but again it does make sense. most things fatigue over time.cheers

you should bleed it at the master cylinder first generally by cracking the banjo and ensure the master cylinder is set up level to pump out all the air

thanks Sulli, tried that too to no avail.




many thanks gents.

[Naked Twin]

Had the same problem on my zx7r, it was a 97 model and had original lines. Rob helped me bleed them and gave the advice and I ended up replacing the lines, it fixed it.

Nick