Front Brakes Dragging - Advice???

Hey gang - '77 Kz650 Custom with triple disks, two on the front one on the rear.

The brakes work great, lottsa life on the pads and I had the rotors ground smooth this season by a machinist. Brake pressure is fine and the lines have been bled a couple of times to make sure there is no air in the lines.

The front brake pads seem like they are not returning to their normal position when I let go of the brake lever. If I squeeze hard when rolling they seem to release properly but eventually ease back onto the disks, not enough to have any effect on the disk but just enough to notice with a little friction noise.

Kawasaki does not sell rebuild kits for this model and I was wondering if I just take the two brake calipers apart and give them a good cleaning is this worth the effort.

Anyone have any experience with this maintenance task? The brake calipers have never been rebuilt and up until now they have worked quite well.

Cheers-Colin Firth-Ontario Canada

Colin, Being a auto mechanic and having seen this problem on cars, here is my thought. The seal around the piston seals and also acts to slightly return the piston away from the rotor. This seal could not be doing it's job but a better reason could be that dirt, crap gets in between the piston and cylinder causing a binding situation to occur. A disasembly and good cleaning may solve the problem, but bleeding (flushing) won't remove dirt as the hydraulic pressure just drives it deeper in between piston and cyl. Let us know...

Hi Colin, go fast and stop bad is a bad compbination.

I second Bluemeanie, with some additional information.

FSM indicates seal replacement every second pad replacement.

You may have some corrosion buildup betrween the piston and the caliper.

Whether you replace the seals or not, taking the units apart and cleaning everything might take care of your binding issues.

The pins might need cleaning and lubrication as well.

Cheers back at ya.

Good advice for sure.

Only I think that some noise is normal.

Colin said: "...not enough to have any effect on the disk but just enough to notice with a little friction noise."

Colin do you actually feel the brakes dragging when pushing the bike around? The real test is does the disk get warm from just running down the road?

KZCSI

Brakes should be replaced/bled every year. When rebuilding the caliper/s, do the master while you're at it, and be done with the whole situation.

Post edited by: CoreyClough, at: 2007/10/01 23:44

KZCSI wrote:

Good advice for sure.

Only I think that some noise is normal.

Colin said: "...not enough to have any effect on the disk but just enough to notice with a little friction noise."

Colin do you actually feel the brakes dragging when pushing the bike around? The real test is does the disk get warm from just running down the road?

KZCSI

The brakes do drag noticeably when pushing the bike, but as far as feeling the disk temperature after a little run I haven't checked this yet. Clearly the pads are still riding on the disk so this leads me to believe that the caliper piston is not retracting as it should.

We've got some rain coming our way over the next few days so it will be a good time to disassemble both front calipers tomorrow and take a look at caliper piston movement. A good thorough cleaning will also be on the agenda.

Thanks gang

Cheers-Colin Firth -Ontario Canada

They all rub some. I can hear mine making little squeeking noises at low speeds as I ride. I remember when they were new, you could prop the front wheel up (or rear wheel on a disc brake model), spin the wheel and feel all kind of resistance. The pads could be manually pried apart with a screwdriver and the wheel would then spin happily until the brakes were applied, then back to rubbing. I'd say yours is normal unless it's really excessive.

Ron - I am a bit of a perfectionist when it comes to certain things in my life. My old bike is one of those things and the rubbing is beyond my tolerance level.

Today I ordered a brake rebuild kit from Jeff @ Z1enterprises. This should solve my problem along with a good cleaning of the caliper interiors.

Just looking to get back to perfection with the old girl until another 30 year old part wears out

Cheers-Colin Firth-Ontario Canada

Post edited by: reborn650, at: 2007/10/02 19:19

I doubt it helps rebuilding, but best of luck and let us know.

As noted by Bluemeanie, interaction between the caliper piston and seal is by design supposed to prevent the pads from rubbing against the disc when the brake returns to relaxed position. Although Colin already understands this feature, some elaboration might be helpful to others interested in this thread.

The shop manual explains that the circular rubber seal around the piston tightly grips the piston. When the brake is applied, the piston does not slide through the seal, but only distorts the seal. When relaxed, the elasticity of the seal resumes its natural shape which returns the piston to its original position (where the piston isn't pushing the pad against the disc).

As the pads wear, the piston will eventually exceed the distortion limit of the seal and slip through the seal, whereby the seal assumes a new grip rest position around the piston, and fluid from the reservoir fills in behind the piston. The length of the lever stoke or pedal stroke remains unchanged, so the brake never needs adjustment.

The seal is made from special heat resistant rubber. (And relatively expensive when compared to the price of a garden variety o-ring.)

Best of luck with the caliper restoration.

Earlier this year I had the master cylinder cause this problem. It would not release the pressure fully with the handle released. If the piston moves back and forth OK, then this would be my best guess.

A little late, but that what I would try next.

I had a similar problem with my 650C1 when I first tried to get it running after it had set for 10 yrs. When pushing it around the garage, I could tell that the brakes were dragging pretty badly. I disassembled and cleaned the whole system, and lubed the sliders. It works better now than I ever remember it working. But I think that lubing the sliders made the most difference. Prior to lubing, I could hardly move the calipers at all on the sliders.