Air in front brakes 75 Z1-B

Hello, Good Morning
I have a 75 Z1-B, We have rebuilt the master cylinder,rebuilt front caliper with new piston & Bleeder screw, new brake hoses, new front brake switch, all new copper washers thruought, new brake hoses, new disc pads, new brake lever, new brake lever pivot bolt, have had the nbrake "splitter" off, carefully cleaned it too etc. Have bled front brakes until fingers are sore, using auto terms have "partial firm pedal", have tried using pump,hold and loosen caliper bleeder screw many,many times still only partial "Pedal",lever stops maybe 1 1/2" from handlebar
if I pump brake lever fast several times it has more
"Pedal" , then when released , seems to revert to partial pedal, using DOT 3 fluid as required, think if I just ride it some to allow new disc pads to seat in it will firm up and amount of brake lever will increase? Any creative ideas on getting air out of system? Or maybe its not Air?
Thanks

zip tie lever to bar over night then crack the bleeder valve

Ed, in the bottom of the master cylinder reservoir cup are TWO holes. The first hole is fairly obvious as it's over 1mm in diameter. There is a smaller hole about 10mm from that hole in a direct line with the master cylinder piston and on the output hose side.

If that hole isn't clear, you will not be able to effectively bleed the brakes. You will need a very fine spike - or a single wire from a wire brush to push thou the hole to clear it.

I had lots of of problems with my '76 kz900 which has dual front disks. I'd alway thought speedbleeders were the answer but they didn't help the air in the lines with the 900. I tried the technique that Plummen suggested and that helped some, but mainly I had to be patient. Every day for a week I'd go out and tap on the caliper and splitter several times with a rubber mallet, holding the bike at different angles. Eventually the brakes became firmer and firmer.

Good luck.

Try using a hand operated "Mity-Vac" to pull fluid/air out of the system.

Thanks Jeff,
We had the master cylinder apart in the parts washer, then bead blasted it and rewashed it, then lastly we used an air hose to blow out the 2 small holes in bottom of master cylinder and used the air hose on the main opening., hopefully we can bleed it once more then we will have more lever. My cousin had tried the wire tie the lever trick last night and interestingly...it did seem to help, not sure what the physics are for that , but if it works i'll take it.
I greatly appreciate all the help I get from you and Chris also. When I get the beginning and finished photos sdaved on a cd., I hope to post them on KZR so folks can see what an absolute basket case it was to begin with and how well its turned out.
We hope to have it finished in about another month.
Regards
ED Spangler

When you attempt to bleed the brakes, the air returning into the reservoir will come up through the small hole. If you are not seeing any little air bubbles, I would run a small spike down through that small hole to make sure it is clear. Nearly every mater cylinder I've rebuild I've needed to do this.

Link14 wrote:

I had lots of of problems with my '76 kz900 which has dual front disks. I'd alway thought speedbleeders were the answer but they didn't help the air in the lines with the 900. I tried the technique that Plummen suggested and that helped some, but mainly I had to be patient. Every day for a week I'd go out and tap on the caliper and splitter several times with a rubber mallet, holding the bike at different angles. Eventually the brakes became firmer and firmer.

Good luck.

I had the same experience. I added a second disk and stayed with the 1/2" cylinder.
Bleeding that system seemed impossible. But after many tries and lots of patience I think the last few bubbles worked their way out and the lever started to work well from the first grip.

Wish I'd been in charge but wasn't.

I'm not arguing.

Bill

Thanks Again Jeff
I followed your advice, then slowly pumped the brake lever with the reservoir lid off, I can clearly see bubbles whenever I pull the brake lever.
So...will try bleeding again and see if lever feel improves.
Hope you, your family, Chris and the gang had a Happy 4th!!
Now I am on to the Gear selector shaft / "Mission Cover" oil Leak, have ordered seals and gasket .If you have any tips for me on what to watch out for when removing the "Mission Cover" and or replacing it would love to hear them, have a thread on that going on the forum engine section.
Thanks Again!!
Regards
ED

all good tips...

the only thing i might ,add or reapet if already said is...

i take long ( 16-18") sections of clear tubing and stick em on the clipers venting/bleeder nipples and run em straight up to the headlight and use somthing to hold em up like that...wire-zip ties ect....then when i'm bleeding i keep tapping and let the fluid stay feeding vertical into the catch tubes (vertical clear add ons) while cracking and pumping and releasing the bleeders..pumping-repeating ect.....eventually with that much standing fluid and wiggleing the lines -tapping the splitter and master and calipers...eventually i can get more bubbles up the exit vent tubes...that last bubble is the ticket....good luck

What also works is buy a new oil squirtcan(the lever type) fill with fluid, then open the bleeders attach the can to it then pump the lever(on the squirtcan). What your doing is reverse filling the system from the calipers up to the master cylinder. This helps push the air up and out, but once the fluid starts to fill the master, be careful as it will quickly over fill! I've had good luck doing this.

The best little tool I found out of various methods is the one way valve designs.... Worked for my ZX6 brakes...

Started with the Napa version (cheap) and worked well but started falling apart... What do you expect for $7....

Have since moved onto the Stockton unit @ Cycle Gear....
Built stringer and have a tighter seal on the caliper nipples (clamp vs. spring)....

Go through the normal bleeding procedures... when you think you have it, open the nipple, pull the brake in/down, velcro strap it in position and tap the caliper and line up to the master reservoirs to get rid of all air bubbles... Lock the nipple down & release the brake. Works every time...