brake piston sticking

i have an '83 kz550ltd and the piston in the master cylinder is sticking.I recently got the bike, and the brakes seemed low, that you could pull the lever almost all the way into the handlebar.I changed the pads and bled the brakes. it started to not return fully, then completely stuck in. i have found no leaks in the system. any idea what could be causing this? is this fixable or should i have the cylinder rebuilt?

There are two ports for fluid transfer between the reservoir and piston bore.

The larger port supplies fluid from the reservoir to the piston bore. It's relatively easy to see through clear fluid.

The tiny (almost invisible) port is a relief port that allows pressure inside the line to relax by returning some fluid to the reservoir.

The tiny relief port might be clogged, and thereby preventing the brake from releasing (i.e., the piston can't return to its resting position inside the bore).

Long story short -- would assue the relief port is clear so fluid may pass through it.

Good Luck!

maybe see if you can find a rebuild kit through z1 enterprises,id check the calipers at same time

Hello, Kevin, and WELCOME to KZR!

We're glad you're here!

Good Luck!

Completly flush the old fluid out, pop the piston out of the caliper, take the seal out, clean the groove with a wire wheel and dremmel, clean the seal and you should be good to go.

Patton wrote:

There are two ports for fluid transfer between the reservoir and piston bore.

The larger port supplies fluid from the reservoir to the piston bore. It's relatively easy to see through clear fluid.

The tiny (almost invisible) port is a relief port that allows pressure inside the line to relax by returning some fluid to the reservoir.

The tiny relief port might be clogged, and thereby preventing the brake from releasing (i.e., the piston can't return to its resting position inside the bore).

Long story short -- would assue the relief port is clear so fluid may pass through it.

Good Luck!

this is exactly the problem I had. Just clean out all of the gunk in the MC and make sure those two holes are clear.