An age old problem......and help required please...

As the title says......

....HELP!

My ZZR600 has shite brakes...

I have googled like a bastard and have done many things to try & ease
this..

I have done the following:-

Installed braided hoses
Changed the pads
Changed the master cylinder
Bled the system numerous times.

I have lost count of the things I have tried....

By pumping the brake lever quickly a few times and then on tight, I
definately get a firmer brake; signifying that it is air and not
mechanical.

It was also suggested to me that I remove a caliper; pump the brakes
very slowly until the four pistons have come out a tadge; clean them
(all the whitish gunk); remove the cap from the top of the master
cylinder and then push the pistons back into the calipers. Brake fluid
then comes back through the system and out of the top, with such force
that it *should* push all the air bubbles out also. It was called
black bleeding. This seemed to work, but the brakes progressively got
worse. (started at number 3 on the span adjusted and ended up back at
number 1 by the end of 3 days)

I also have tried the bungee trick; this gave a lot better brake; and
after 100 miles the brake was as spongy as before. I did the bungee
trick again the following day and again after about 100 miles, back to
sponge-city.

I have now run out of ideas, and am thinking that air must be getting
into the braking system somehow...anyone got any thoughts/suggestions
on this??

TIA

 

You installed new lines? It's possible air is trapped somewhere, try tapping
the fittings with a hammer, or shaking the lines to try and dislodge the
air.
You could also try filling the system upwards from the brake caliper with a
big syringe, maybe a good idea to put some Copaslip on the nipple threads to
stop air seeping past said threads.
Also, Mityvacs are v.good.

 

I've never found a really easy way of doing this. What I actually use
for blowing out the pistons is a cannibalised soda stream machine
i.e. the CO2 cylinder plus push operated valve with a short length of
1/8 nylon tubing attached but I'd have thought an air line would do
the job. In addition I have a selection of pieces of rubber, bits of
wood, G-clamps assorted and a large woodworking vice for blanking off
holes as required (The caliper mounting bolt will fit the brakepipe
union bolt hole to seal it). If you find you manage to pop one
piston and not the other covering the removed piston with sheet of
(say1mm thick) rubber and clamping lightly back just into the end of
the bore can make a good seal. I've always managed to get pistons out
using compressed gas (I did once resort to heating) but *ensure* the
pistons are not able to fly unrestrained from the caliper as they can
let go with a bang.

One of these day I'll make myself a kit for doing this job. I think
what is required is a blanking plate/flange for the small connecting
hole connecting the caliper halves with some sort of valve/union for
connecting gas/hydraulics but I've never seen anything suitable on
sale.

HTH

Jim

 

Blank the spare hydraulic holes off with the right sized bolts if more
than one hole to the calliper. On one hole either use the bleed nipple,
if it fits[1] or screw in a grease nipple if the thread fits the
hydraulics' hole.

Wrap the lot in a sturdy cloth to stop bits flying about when it comes
apart.

Connect the largest grease gun you can get hold of to the nipple and
pump. If there are two hydraulic holes in the calliper pump out as much
air and replace with grease before sealing off the second hole.

It will come apart or the calliper's casing will split open [2] as the
piston will have several tons pushing on it.

You must wash the lot out in meths as you will have polluted everything
with the wrong sort of oil based product.

[1] Fits the grease gun.
[2] 6 to 10 thousand psi grease guns are common my Draper is 8000psi.