Z1000 A2 Rear Brake Master Cylinder

[Kev1R]

Z1000 A2 Rear Brake Master Cylinder
Worked till I took it apart – I know “if it ain’t broke don’t fix itâ€￾ .............it was kind of working but not very efficiently – now not at all.

Master Brake cylinder not pumping fluid –I know these can be difficult to bleed but I cannot get fluid to even to the 1st banjo connection to the side of the unit.

I seem to remember a thread relating to possible blockage in the unit - not sure where I should be looking though – is this potential blockage somewhere in the bottom of the reservoir – this seems to have a non removeable plastic cover and difficult to check from the top.

I have a replacement parts kit from z1 enterprises that I will attempt to fit over the week end.

Anyone done this (removing the piston) without access to an airline - I am anticipating an interesting week end of further challenges!
Would appreciate any guidance.

[Kev1R]

Got it apart with a bike pump to access primary cup & spring.

All looks good and clean
Took my time cleaning and coating with brake fluid before re assembly.

Put it all back together and tried again - exactly the same result.

There are only about 6 moving parts and it all looks to be ok - except it does not work - Very frustrating!!

[chrisu]

you need access to a vacuum bleeder like a mityvac

this will drag the fluid through

[Kev1R]

The fluid is not even appearing at the outside of the master cylinder where the 1st banjo connection for the brake line is bolted to the side.

I had discounted it as a 'bleeding' issue and more of a "piston not doing it's thing" issue.

Strange the set up looks similar if not identical to the Z1R one which I replaced all moving components about a year ago with no problems at all.

Thanks anyway - I shall keep at it

[chrisu]

Had exactly the same symptoms and mityvac was how I fixed it

[Kev1R]

Ok Chris you've convinced me

I shall invest in a vacuum brake bleeder

Thanks for info
Kev

[chrisu]

took a while even then

the alternative is to use a syringe to prime the brake line

[scott]

Kev there are two tiny holes in the master cylinder, make sure these are clear, think one is called a relief hole. A very fine piece of wire should open up the hole, which is probably full of shite......had the same problem on my A2.

[Kev1R]

I had read somewhere about blockages - presume these are the holes in the inside of the master cylinder which join the piston area to the fluid in the reservoir.
A Blockage there would certainly account for the symptoms but unfortunately the 'floor' of the reservoir has a plastic base which looks as though it is not made to be removed - otherwise access to clearing any blockage would be straightforward.

I then read that the entire plastic reservoir bit simply unscrews from the metal body -but I have not managed to do that either. I expect it could be a blockage and the vacuum simply overcomes it to force it out and clear.

[chrisu]

might be a red herring............

i had dismantled my master cylinder as it was the bleed hole was blocked and causing the rear brake to stick on.

bleed problem was after it was fully dismantled, cleaned and reassembled.

[scott]

I had read somewhere about blockages - presume these are the holes in the inside of the master cylinder which join the piston area to the fluid in the reservoir.
A Blockage there would certainly account for the symptoms but unfortunately the 'floor' of the reservoir has a plastic base which looks as though it is not made to be removed - otherwise access to clearing any blockage would be straightforward.

I then read that the entire plastic reservoir bit simply unscrews from the metal body -but I have not managed to do that either. I expect it could be a blockage and the vacuum simply overcomes it to force it out and clear.

The plastic base, if I remember correctly, has a little piece of plastic floating about the bottom. Wip it out with a little piece of bent metal and there should be two screws revealed. Undo the screws to remove the reservoir.....if I remember correctly

[tlc]

Scott is correct.
Using a right angled pick to pull upwards on the plastic part inside the reservoir at the bottom. Underneath that are 2 screws which then allows the reservoir to be separated.

[Kev1R]

Update!!

Removed the plastic base with a small allen key - Could easily see the two screws that release the base but as they are made of something resembling the consistency of Philidelphia Cheese I could not unscrew them.
In the meantime the vacuum bleeder arrived in the post. The method that eventually worked for me was:

1 attach the vacuum bleeder to the caliper in the normal way
2 remove the brake line connection to the master cylinder and place in brake fluid container and then draw fluid through the line with the bleed device.
3 using a finger on the side of the master cylinder (Where the line connects to) as a pressure relief valve, pump the cylinder -with the brake pedal- until you have fluid up to that exit point.
4 re connect the (now full of fluid) brake line.
5 bleed in the normal way using the pedal (I found it better if the plastic drain tube from the bleed nipple went 'up' an inch or so before draining down to give a little surplus fluid above the nipple.
This worked for me


Incidentally the piston that came in the kit was different dimension (Slightly too big) to the one in my bike so I could not use it.

Thanks to Chris and all advice- for inspiration to persevere as I had almost given up and was on the point of investing in a replacement master cylinder.

[chrisu]

Good result.

Excellent

[Taffus]

Update!!

Removed the plastic base with a small allen key - Could easily see the two screws that release the base but as they are made of something resembling the consistency of Philidelphia Cheese I could not unscrew them.

You need to use JIS screwdrivers not philips. Philips are designed to "cam out" ie chew the heads if too much force is used. The Japanese use JIS standard screw heads which are very different to a philips head.

You can of course bodeg the job and hit a philips screw driver into the JIS screw and gorilla it out...........