brake bleeding problem

Have just put together the front brake system on my project bike.
New pads, new seals in the callipers, lines were totally dry, been sitting for a few years, banjo bolts were all ultrasonic cleaned and blown with compressed air as were the lines..
master cyl from zzr 1100 (5/8"). Stripped the master cylinder before putting on and cleaned accumulated sludge out seals looked ok.

bled the entire system multiple times. even started at the top cracked all the fittings and bled them all the way down. Have put about half a litre of fluid through, no air.

problem is the lever isn't creating enough pressure, blanked off the master cylinder with a bolt and washer and it is rock hard, kinda ruled the master cyl out.

there are no leaks in the system, i even tried bleeding it with a vacuum pump.


i am at a loss. I don't think the old rubber lines would flex that much.

ideas would be much appreciated.

Try holding the calipers up over the MC. Have a buddy crack the bleeder and check for air. It took me almost two weeks to get mine bled doing it with the calipers on the forks.

I use a pressure bleeder tank (KD 2222) with a special adapter I made. This works really well as it pushes fluid through the entire brake system with both bleeders open at the same time (no air bubble can get trapped). If you know a professional car mechanic you may be able to gain access to a pressure bleeder. You'll just need to make your own adapter as I've never seen one for bikes. Ed

am at a loss. I don't think the old rubber lines would flex that much.

Wanna bet??

I just put GPz750 calipers and a 96 GPz1100 master cylinder on my 750 twin using 80 KZ750E brake lines. No matter what I did (and I tried all the tricks) I still couldn't get them to work. Sure could watch the brake lines dance around when I squeezed the lever though.

New Stainless brake lines solved that problem. And they don't move a bit when I squeeze the lever.

Post edited by: steell, at: 2007/09/17 19:44

Rubber lines can deteriorate internally, swelling shut.

It is possible the brake lines are collapsed inside or have a( Butterfly)a piece of rubber inside the line that is acting as a one way valve.

Remove the calipers from the bike...hang them at a slightly different angle than they were when installed...slip a piece of wood a little thicker that the rotors in between the pads...hang them above the master cylinder,and bleed them again.
That's what I had to do,to get Mine bled on My bike.
I tried for DAYS,to bleed them while they were still on the bike,to no avail.Tilting them slightly made all the difference.Try to get the bleeder valve to the highest position,and just play around with different angles and You will get it.There's a pocket in there that holds a bubble and You won't get it out unless You do this.
Good luck with that,and post back.

Not clear to me what calipers you are using but the ones on my 1981 1000J gave trouble with binding on caliper slider pins. This pulled the calipers back from the disk giving excess clearance and as a consequence too much M/C lever travel.

I had replaced lines M/C kit etc etc and still had spongy brakes until I had a look at these sliders. On mine one of each pair had an anti rattle sleeve and it looked as though my lubriaction had made these swell leading to binding. Replaced with new at a cost of a few cents and removed lubricant. Sweet as since. Howwever this is a bizarre problem so check fluid for air first as suggested above.

Post edited by: Kiwiz, at: 2007/09/23 16:05

search the forum for "gravity bleed" - works great!