TOPIC:

Bike:
'83 KZ750F1

Symptoms:
Front brakes drag at random. Some times a little, some times so bad that I need to go full throttle just to pull over to a safe place. At that point, I could crack the bleeder just a little to relieve pressure, and barely get home before it starts again.

Brake lever feels... strange. Definitely feels stiff, with very little travel required to actuate the brakes. Piston often doesn't return far enough to disengage the brake light switch.

At first, the dragging only seemed to be on the left caliper. I rebuilt and cleaned out the left caliper, and flushed the whole system... now it drags on both sides.

Does this seem like a master cylinder problem? If so, how do I take the blasted thing apart? I can't figure out how to remove the piston once the dust cover and retaining clip are out, and the factory service manual is no help.

Rebuild the calipers, the pistons are sticking. Cause is old brake fluid. Now is a good time for new pads as well.

I would rebuild the master cyl. and the other caliper. If you do then make sure that both holes inside the master cyl. (ones larger than the other) are clear. BTW I like Bel Ray Super Dot 4 brake fluid.
Sorry, I didn't read the whole post. My Clymers manual Isn't too detailed about the front master cyl. I'll have to check with a friends factory manual. But that won't be until later tomorrow. Sorry. My guess is that you might just need to latch onto the end of the piston (pliers small, vise grip etc...) and pull. Do hone the master cyl. once you get the piston, spring. and other parts out.

Post edited by: zedheadmc, at: 2005/11/01 00:36

Post edited by: zedheadmc, at: 2005/11/01 00:38

Post edited by: zedheadmc, at: 2005/11/01 00:45

I'd say if you're master cylinder won't come apart easily if the retaining clip is out, then that is probably the cause of the sticking. The piston assembly should come out easily. If not grab hold and yank. Since you're getting a rebuild kit anyway, all that stuff gets replaced.

It wouldn't hurt to at least tear apart and clean out the other caliper. When the rubber piston ring is out, make really sure its groove in the caliper is as clean as you can make it. All that white powdery junk has to come out. Anything in that groove causes the piston ring to squeeze on the piston tighter than normal. Also, The piston rings are directional (tapered), so pay attention, I think the fat end goes toward the pad... isn't that right?

=

Yep, it looks like you just tug on the piston once the dust cover/retaining clip are removed.

Think I got it... there was so much of the white crud on the outside of the piston that it actually formed a ring around the top of the cylinder. It looks like that's what was causing the piston to not fully return, as well as causing the difficulty in disassembly. I was able to carefully scrape most of the crap off with a pocket knife, taking time to go smoothly and evenly without gouging.

Test ride seems promising, but brakes are now pretty spongy. I'll re-bleed the system and test again to be sure. Thanks!