Front Brake Lever is Floppy 82GPz750

Now that my 1982 KZ750-R1 (GPz750) is running well its time to work on getting it to stop. The back brake is very acceptable.

Can brake lines get so old that they let in air without leaking fluid? What should I replace first? What can be replaced with used parts? What needs to be replaced with new parts? Is there some kind of piston that should be snapping the break lever back into place?

The front brake hand lever is floppy, and I use a bungee cord to hold it out. When I pull the lever it feels very soft and the pads just barely grip the disk. The pads show very little wear although they have been on the bike since I got it in 2005.

The master cylinder assembly looks o.k. from the outside, and there is no fluid seeping out. The right caliper assembly is missing one slider. I noticed that there was some kind of oily fluid at the end of the right front fork. I couldn't determine where it was coming from. The end of the left front fork is dry.

I replaced the brake fluid last year and bled the brakes extensively, but there always seemed to be a couple of more bubbles.

When brake lever is released, a spring inside the master cylinder pushes the piston back to its beginning position. Things may be too gummed up inside to allow the spring to do its job.

Brake lever itself could be worn out or damaged -- not able to push the piston in far enough, or not situated close enough to the piston when at rest (should be only slight clearance between lever and piston when in rest position). Might even be the wrong style brake lever from a different model bike.

With lever removed, test movement of the piston by pushing it (hard) and watching it return. It should move about 1/2 inch back and forth.

May be time to disassemble and overhaul master cylinder -- should obtain and use shop manual for guidance.

Brake lines won't let air in without leaking fluid. The lines are likely okay, at least until first getting the rest of the front braking system up to snuff.

Fluid at end of right front fork is probably either brake fluid or fork oil. Suggest cleaning the area well, letting dry, and watching carefully for any escaping brake fluid as brake is applied. If no brake fluid leakage, try pumping the forks to see if there's any fork oil leakage. If no fork oil leaking, check the fork oil level to assure fork has any oil left in it.

Uncertain what is meant by missing one slider. Hope not referring to caliper shaft -- but sounds dangerous to have missing, whatever it is. Any motorcycle with less than perfect brakes is too dangerous to ride. So please don't.

May be time to disassemble and overhaul brake calipers -- do both of them -- and use shop manual for guidance.

Please Please PLEASE do not ride the bike until the front brake system is repaired, whether by you or someone more professional, and fully operational. This is the single most important mechanical control on a motorcycle.

If there's any doubt, have the brake work done by a competent professional (and just maybe save your life).

Hoping, sincerely hoping, for a successful repair.

Post edited by: Patton, at: 2007/05/16 17:06

Post edited by: Patton, at: 2007/05/16 17:08

Thanks, and Thanks.

I'll do the research, and tear down the master cylinder this weekend, then report back what I find.

I might have a plastic cup master cylinder assembly from a 1982 KZ750 LTD that is in better working order. The one on the bike is a metal box, and looks cooler.

I'll have to see what is broken and how much replacement parts will cost.

I'll get backt to ya.