Help,,Brakes on 79 kz400

So here the situation -
Caliper is in tip top order..
Pressure at the lever for the brakes....I have tried both of the master cylinders that I have and both seem fine.
Brakes bled and bled well...no air,
No leaks
Almost no stopping power at the caliper
Looks like the piston is extending but the inner pad doesn't make any contact.

Am I right in assuming that a new set of pads would be a good place to start ??

Should have mentioned the problem is with the front brake

Your saying the brake pads do not contact at all? Are the pads within spec or are they worn all the way down? Can you get it to grab the rotor if you pump the brake handle?

Assuming you checked the brake reservoir and the fluid is up to where it should be?

I haven't worked specifically on a KZ400, but almost all older Kawasaki are a single piston caliper. The piston pushes only the outside pad. The inside pad is is fixed against the caliper. The caliper floats on pins/bolts of the mount, centering on the rotor by the outside pad. The brake caliper lives in a dirty wet environment. Corrosion and and grime are a common problem. However, short of being rusted solid, a properly working M/C and piston should have enough force to overcome the worst rust and grime. Then the problem is the stuck caliper won't release the inside pad from the rotor. You may have a combination of problems. For starters, you need to remove the caliper and make sure it "floats" on the mounts to start. I think you may find that you don't have as much piston pressure as you think.

MDZ1rider wrote: I haven't worked specifically on a KZ400, but almost all older Kawasaki are a single piston caliper. The piston pushes only the outside pad. The inside pad is is fixed against the caliper. The caliper floats on pins/bolts of the mount, centering on the rotor by the outside pad. The brake caliper lives in a dirty wet environment. Corrosion and and grime are a common problem. However, short of being rusted solid, a properly working M/C and piston should have enough force to overcome the worst rust and grime. Then the problem is the stuck caliper won't release the inside pad from the rotor. You may have a combination of problems. For starters, you need to remove the caliper and make sure it "floats" on the mounts to start. I think you may find that you don't have as much piston pressure as you think.

Yup, the caliper and piston work beautifully.. I think the inner pad may be too thin and worn..i can see the outer pad moving with enough pressure to move the rotor a little...

punisher11b wrote: Your saying the brake pads do not contact at all? Are the pads within spec or are they worn all the way down? Can you get it to grab the rotor if you pump the brake handle?

I can get it to stop the rotor if spun by hand, but i still see a gap on the inner side.. piston had enough pressure to move the rotor in a little.

If the inner pad looks thin I would change it, seems like the likely place to start. Make sure your guide pins/bolts are lubbed. Just out of curiosity does pumping the breaks cause them to stiffen up at all?

they are pretty stiff on the first pull...Im almost positive there is no air to sponge things up....I just ordered a new set of pads....I may try to craft a small shim just for trouble shooting to see what happens... Ill keep an update going.

Its a long shot but have you tried zip tying the brakebhandle in and letting it sit overnight? Helps retrain the caliper to the correct position.

If the outer pad is contacting the rotor enough to make the rotor move and there is still a gap between the inner pad and the rotor, then the caliper is not moving as it should. Could be corrosion or something could be binding.

Wait. Only the pad with the piston actually moves. The other is locked into the caliper. The caliper should move slightly on its pins when the piston drives it's pad into the rotor.
That expansion action pushes that pad and pulls the caliper housing, with it's fixed pad, to the other side of the rotor.
Did I misunderstand you about one pad not moving?