z1 73 disc pads sticking on (twin disc)

[slacker]

Hi all, I have just rebuilt the bike including the brakes.

I have fitted a new master cylinder, rebuilt both calipers fitting new seals and use the old discs which look fine to me. I have just taken the bike out for its first run since the rebuild. During the ride the front brakes would not release and the disc got bloody hot. When I rebuilt the calipers should I have lubricated the 2 bolts which locate the moving pad. I used DOT 4 brake fluid when I filled up the system. Anyone got any ideas why they are not releasing.

Thanks Ian

[tlc]

I think the easiest way to tell what is happening is to remove one caliper at a time and see if the piston returns whilst holding with fingers.

I have seen either master or slave giving the problem you describe with possible causes being too tight a tolerance for the seals.

Is the new master a genuine or repro ? Was the caliper seal receiver totally clean ?

[slacker]

Thanks for the reply chris,

the master cylinder is a repro from z1.

I did clean the calipers prior to fitting the seals. I'll strip them again and make sure they are totally clean.

Ian

[PAULJAC47]

A clue to check if hydraulic or mechanical fault is to check if the brake pressure switch is breaking and putting indicator lamp on/off,and yes you should lighty grease bolts with copperslip.caliper shoud slide freely on bolts. Paul J...

[coldsummer]

It's not unknown for the new pads to have too much meat on them and may need to be 'reduced' slightly. Also, twin discs are slightly thinner than the single disc. Has yours been converted from single to twin using another thicker single disc?

Disclaimer - I don't consider myself an expert, just passing on some thoughts that may be worth considering

[RogerJ]

It's not unknown for the new pads to have too much meat on them and may need to be 'reduced' slightly. Also, twin discs are slightly thinner than the single disc. Has yours been converted from single to twin using another thicker single disc?

:

Hmm, my Z1A was converted to twin discs when I bought it and has the 7mm discs fitted. All other parts are new, including the ZPower calipers, and they still drag. Time to try 6mm discs methinks. Thanks coldsummer for the tip.

[PAULJAC47]

It's not unknown for the new pads to have too much meat on them and may need to be 'reduced' slightly. Also, twin discs are slightly thinner than the single disc. Has yours been converted from single to twin using another thicker single disc?

Disclaimer - I don't consider myself an expert, just passing on some thoughts that may be worth considering

Good point Simon,just fitted some 5mm discs to my A4,much lighter as well!!!

[RogerJ]

Anyone know if Z650 discs will fit?

[GPRD]

I found a similar thing when I was doing my 650. The bolts holding the floating pad should have rubber boots on them, what I found was that when I was pusing the bolt through when assembling the caliper, I was trapping a bit of rubber, not allowing the bolts and floating pad to move freely.
I hope I explained myself properly there, I did try to avoid saying 'thingy'!!!

[zedtwo]

Z650 Discs will not fit as they are 4 mounting bolts and Z1s have 6

[PAULJAC47]

If not too fussed about originallity an A4 wheel fits right in with the more commonley available discs!!!!

[RogerJ]

time for me to look for a complete A4 front wheel then. Thanks for the info. Anyone got one for sale by any chance?

[PAULJAC47]

You may be in luck send me a Pm..Paul J

[slacker]

Hi guys,

Thanks for all your help.

I have removed one half of each caliper and then pulled the brake lever and both pistons go out and then drop back, but the floating pad stays out. The replacement pads are jamming in the carrier. I've filed the pad diameter down and they now appear to be working. I give the bike a run tomorrow. I'll stick so photos on the site of the finished bike.

Thanks again Ian