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Paul,

I find most bike front brakes bleed pretty quickly anyway due to the master being so far above the calipers (gravity).

The rear master cylinder on a Z13 will allow fluid past the master piston if you reverse bleed..........I did it 2 weeks ago on mine in a very short time.
Just ensure you have a small tolerance between the end of the piston and the linkage arm so the piston is at its maximum stopping point.

Not sure which fluid you are using, but I use DOT 5 Silicon Fluid on mine as its 100% non corrosive so does not eat your paintwork if it gets on it.
You can only use Silicon Fluid if your system is completely drained of conventional corrosive fluid, as you cannot mix the 2 together.

Pete F
UK

Ok, front brakes have been thoroughly bled, but I still have a lever that goes right down to the handle. It does stop the bike though, so something is happening, but no pressure like I am expecting and like what I have on other bikes. There is definitely no air in the system anymore as I bled it all the way in reverse and then for good measure half a litre the conventional way.

The rear will not push through the MC. I stripped it and it all looks fine, but as soon as I put the piston in, it blocks.

Could it be that one of the holes inside the bore is blocked? And if so, how to unblock?

I am now leaving it as I am frustrated and the brake fluid needs to rest.

The lever on your front brake may not offer the piston enough "stroke" to fully pressurise the system.
Try removing the brake lever and using a phillips screwdriver in the piston cup and push the screwdriver instead of the lever.......it usually goes further in.
That has worked well for me on other bikes.

With the rear, you should have 2 holes in the bore just like the front but its a bit more difficult to see them due to the upright design of the master cylinder.
You can carefully use wire to clear the holes but obviously just be sure the wire does not touch the seals on the piston.
Its important to be sure the piston is stopping in the correct position to be certain the piston stroke is passing both holes in the bore.
You should definitley be able to backward bleed it from the caliper to cylinder as I have not had a problem doing it on countless Z1300's over the years.

Pete F
Uk

I am at work now so can't look at it, but whilst I don't wish to question your wisdom, ...are you sure there are two holes in the bore? I can see two in the reservoir, but I had a really good look and poke about with some metal wire (without scratching the bore of course), and I can only see one hole in the bore. Once the piston goes in, the system is blocked and I cannot get anything through from the rear caliper connection into the rear MC reservoir.

I'll have another look when I get home and the other thing I will do is inspect every component to see if it is assembled correctly.

Paul

There are always two ports in a conventional brake master cylinder, one of which is located in front of the piston. The front port, sometimes called an equalizing port, allows fluid to move back into the master cylinder when the brakes are released. If that port get plugged - which is not uncommon if the system has not seen regular maintenance, the effect is the brakes will drag and even lock up (as the fluid heats and expands and the port is not available to bleed off the excess pressure.

If your lever is really spongy, you still have air in the system. Typical places where the air gets trapped are:

• in the master cylinder piston cavity. Puling the lever in then letting it snap back (and keep repeating until no air bubbles comes out of the ports can help with this.
  
• at the end shoulders of banjo bolts - 'bolt bleeding' each of the 5 banjo bolts (starting at the top) can help with that - it's messy though so you need to be extra careful not to get brake fluid on anything. The fluid holes on ends of the factory banjo bolts on my mid 80's Honda are dimpled (or countersunk) to eliminate the shoulders. I do this mod on all banjo bolts. You can buy special banjo bolts that have build in bleeders which will help with air trapped in the banjo itself - I've never used them so not clear to me if they provide any benefit or not. Pete's mention of DOT5 fluid is good advice (and works especially well for bolt bleeding) but it'll get you into never ending flame wars on the internet.
  
• at the caliper seals which is much harder to get rid of because the seal cavities can trap air that is 'blind' to the bleeder screws. Ensuring the cavities and seals a whetted with brake fluid helps with this when assembling brakes). Driving around for a few days to shake some of the air loose - which then has to be bled using the bleeder screw - may help.

After not being able to see it I decide to take the plug out and indeed there are two holes and indeed one was plugged solidly!



When trying to unplug the second hole it was really solid, so much so that it seems to have been plugged in purpose?? I think in order to open it up I need to drill it out, but before I do that, are you sure there should be two holes going from rear brake mc reservoir into the mc piston bore?

I also created the air box, but it keeps slipping off. How did you secure it?