Help! front brakes won't work

Please help. I have a 77 KZ650C with the dual font disks. I cannot seem to get my front brakes to work. I have rebuilt the both calipers and the master cylinder twice. No matter how many times I bleed them the lever always feels spongy, and will not fully apply the brakes. I tried reverse bleeding with a large syringe and I also tried zip tying the brake lever closed over night but neither seem to help at all. I know that the calipers are functioning correctly and the master cylinder is not pitted. If anyone has any suggestions please let me know, since this is driving me crazy.

i installed new lines and it took FOREVER to get the lever back...if you have the resevoir that has the 4 screws holding it on it will take a while..
it took about 2 hours and a lot of fluid..start at the caliper farthest from the master.....hope this helps.....good luck

The last time i had his problem I had air bubbles trapped in the master cylinder. I tapped the master cylinder and a few bubble came out then I removed hte master cylinde unit and turned it the air bubbles came out and problem solved.

If the bleeder screws aren't situated at top of caliper in its usual mounting position, sometimes helps to remove the caliper from the fork and hold it in position so the bleeder screw is at the top while doing the bleeding operation. This helps expunge any air which might be trapped inside the caliper above the bleeder when in the normal caliper mounted position.

This is the FSM specified bleeding procedure for KZ900 LTD.

Good Luck!

can only be 3 reasons for you problem, you have air in the system, the MC is bad or the MC is/was not designed for dual
disks and can't move enough fluid.
since you say that the MC is good and and you have tried about everything to bleed the air, you should disconnect 1 of the caliper hose at the junction block ( make sure to plug the opening) and rebleed the system.
If the lever feel good and the brake work, obviously the issue is with the wrong bore in the MC

Thanks for the help. If the master cylinder is too small to move enough fluid would that effect the lever feel or would it just not engage both calipers completely.

that will do both, the lever will feel very soft and the volume of fluid pushed by the MC piston will be too small to fully displace both calipers pistons.

bleed the brakes some more;)