Can't bleed KZ750 H2 after caliper rebuild?

I have just rebuilt all three calipers on my 81 kz750 h2.

New seals and boots, and some new lines.

I am unable to bleed the brake, both front and back.
I must have gone through 2 quarts of brake fluid already.
I bleed and bleed, and get a few small bubbles to come out of the right caliper, then the left caliper, then nothing, unless i wait a few hours. But i have been doing this for almost a week now, and still have zero brake power\pump pressure. Not even started on the rear.

I am unable to take out the piston of the master cylinder, because the circlip is so badly corroded, but i have done my best with compressed air, and made sure both return holes in the master cylinder are open.

I get some air the come out of the MC reservour after refilling but thats about it.

Am i doing something wrong? I see no leaks anywhere in the system.

Any help is welcome!

they make a tool for drawing fluid from the bleeder.... harbor freight...or harbor F onmline


try tapping the the lines and junctions with a rubber mallet while you have the lever held in,just before you crack the bleeder...bleed the junction /splitter union bolts

bleed every nut and line coupler...crack it while the lever is held in...start at the bottom bleeders and work your way to the master cylinder ,cracking or bleeding any fitting...then reverse the order....you will get the air out and just a small size bubble can make a huge difference

OK,

I have cleaned out all hoses, and air pressure cleaned out the junction section with all pressure screws, bleeder screws and MC hose and screws.

I have been using the mighty vac all night long now, and have tried to use it to bleed both of the front disks, with no luck. When the pump is hooked up it seems as though there is air coming out of the caliper ALL the time, i dont get it. i must have ran a liter of brake fluid buy now and no change in MC pressure. Whats going on???

Please help

Might be time for new mastercylinders if theyre too coroded to take apart imagine what internals look like

krifartida wrote: ...I get some air the come out of the MC reservour after refilling but thats about it.....

With the brake line banjo removed, squeezing the brake lever should press against the MC piston to force brake fluid out the exit hole where the banjo attaches.

If only getting air (instead of brake fluid) out of the exit hole, the piston bore isn't being filled with brake fluid (for whatever reason) from the reservoir.

If there's fluid in front of the piston cup inside the bore, pressing the piston against the fluid will push the fluid out the exit hole.

Good Fortune!

What was the situation with the brakes before beginning work on the calipers?

If only air is coming out, where did the 2 quarts of fluid go?

Good Fortune!

Before all three pistons were seized. There was considerable amounts of brown sludge in all three calipers, and all seals and boots were dead from dried out brake fluid..

When the mightyvac is connected it sucks brake fluid out, but it always has some air bubbles in it, all the time.

The piston is pushing out brake fluid, as i am able to bleed the fluid from the bleed valves.
I bleed and bleed, but no air bubbles appear to come out when bleeding manually. i keep topping off the reservoir so it does not suck in air. I have teflon around the bleed valves as i heard that might help, but i guess its not really doing anything.

Is it possible the MC piston is letting in air through somewhere?
I just ordered a pair of circlip pliers, which i hope will help remove the MC piston circlip and the piston it self for inspection.

Try stripping the master cylinder down as far as you can then soak the rest of if in a pan full of brake fluid,yeah itll remove all the paint but hopefully it will loosen up the snap ring enough to come out so you can rebuild it.
or you could probably buy a good used one for $20-30 someplace thats rebuildable if need be

A. If you have Speed Bleeders on your calipers, remove them and use regular bleed valves. Speed Bleeders are only for maintenance and won't let you flow enough fluid out of the calipers to bleed after a major rebuild.
B. What is the state of your MC's? Based on the description of your calipers before the rebuild, they are most likely shot. Get new ones if you're not able to completely rebuild the ones you have. Your life depends on it.
C. Don't use that MityVac gizmo! Reverse bleed your brakes instead.
D. The splitter that is on the lower triple-tree always gave me fits because the front of it sits higher than back and a bubble of air likes to get trapped in there. You'll have to figure out a way to tilt it so that the banjo fitting holding the hose going up to the MC is the highest point on it. When you combine that problem with skinny SS braided lines, Speed Bleeders, and the MityVac, you end up wasting a lot of brake fluid trying to move that bubble out of there to no avail.

A word to the wise, never rebuild both the front and the rear brakes on your bike at the same time. I know yours is a different situation but under normal circumstances, that is a recipe for disaster.

OK - so i have pulled the MC apart, finally!

Inside was dirty with lots of sediment, but no apparent damage. All bores were smooth and action was good.

Cleaned all and put back together - but had a hard time getting air to rise out of the reservoir, but after lots of tapping with a mallet on the junction section, and the calipers them selves - all the air finally rose out, and i was ready to bleed.

But - shocks- just as before - i bleed a few boubles out the right side caliper, then nothing more. I bleed a few more out of the left side, and no more. I used the mightyvac again as well - no effect. No clue what to do next???? where is the air hiding, and why is it no coming out???

Rear brake bled no problem and action is good BTW.

bench bleed the master cylinder first

I did...