1977 kz1000 stock brake refresh

Hello
 I am looking at doing a brake reshresh on my 1977 kz1000.
I think that the pistons in the rear caliper might be stuck. Does any one know if this stock caliper and piston are hard to fix ? I am looking for any advise or tips on properly fixing  and restoring the brake calipers.
Thank you for reading this!
have a great day !😀

Brake callipers are pretty straightforward to rebuild and I believe parts are readily available for your KZ. The main thing is "surgical" cleanliness when working with hydraulic internals. If the calliper is frozen take the pad out, slide some cardboard between the rotor and the piston and apply compressed air through the bolt hole for the hose fitting - with luck the air pressure will force the piston out "WARNING" don't be tempted to poke your fingers in there when applying the air, if they get caught between the piston and rotor they won't be much good for anything afterwards

Good Morning GD! Those opposed piston Tokico 1977-1978 rear calipers can be a bear to service if pistons are stuck. Can You verify which, if any, piston is stuck? Both outer and inner A and B sides share the exact same piston/packing and dust seal components. Because the pistons are stubby little things if bore is all corroded and worn they can get cocked in the bore. I've also seen a few times over the years where persons adjusted the brake pedal too tight, taking out that "Required" freeplay! This absence of play and if brake pedal pivot to frame is rusted/old grease, the master cylinder piston won't retract back to it's resting position. This episode or portion thereof keeps the "relief" port shut in master cylinder resulting in what feels like a stuck brake. They used similar Tokico systems on the GS1000 and i believe some smaller GS's, both calipers of the clamshell design.       

thank you Clay!
Right now the pads on the rear brake are jammed up tight to the disc. I am not sure if I can disconnect my brake line and the I can try using a vinyl wedge and tap the wedge between the disc and the pad. Do you know any other ways to proceed ?

Compressed air can pack a lot of energy.  I have seen them popping out and flying across the shop, smashing things as they go.  An alternative is to attach a grease nipple and use a grease gun to force the piston out.

YES, open both bleeders while still attached. See if that relieves the pressure. You can pop off that plastic panel and get in there and spread the pads. And..everyone is mentioning "Air" to pop out those buggers. Yes air is fine and WILL bite you if not careful. I use a grease gun and specific grease Zirk fitted to the 10mm input. Gets the worst ones our...gradually, no surgery required!   

asphalt900 wrote:

YES, open both bleeders while still attached. See if that relieves the pressure. You can pop off that plastic panel and get in there and spread the pads. And..everyone is mentioning "Air" to pop out those buggers. Yes air is fine and WILL bite you if not careful. I use a grease gun and specific grease Zirk fitted to the 10mm input. Gets the worst ones our...gradually, no surgery required!   

Probably worth mentioning if you do need to go the "Air" route and especially if you are doing it "off the bike" then clamp the calliper in a vice and use pipe grips or a clamp to control how far and how fast the piston comes out (don't want any mishaps from flying objects)   whichever route you go down try and avoid "mechanical methods" if you intend to re-use the pistons

A couple pics. Here's the two different "styles" of Rear Calipers used on the 1977-78 KZ1000 models. Your Bigger style is for the A model and single piston style was slated for the B or LTD model. As Wookie mentioned Don't resort to grabbing the piston with vicegrips!! Another "subcategory" of the Bigger A model used phenolic inset pucks on the Z1R 1978 pistons, still 43mm diameter though but      didn't use the shim plates. Note in picture those "labeled Suzuki" pad shim plates X2. This is where Suzuki shared the same DNA with Kawasaki during this era. Kawasaki part number would be 43076-004 for this shim. Pins/pin retaining clips and brake pads interchanged too. Only thing that didn't was the flat "ring seal" between the halves, Suzuki was smaller.    

Sounds like a full system teardown is in order.  The corrosion that causes piston sticking, will also damage the master cylinder, and leave a scale inside all the parts, including the brake lines, which BTW, should be replaced.

 

Thank You for all these great ideas ! I am sure I can get this back in order now .
Have a great Day today !

As ever:  Well explained, Nessim, hardrockminer, Guy and Clay!   That all will help unexperienced persons on a sensitive theme like "brakes" a very lot !
( I´ve done it this way by myself a very few times: Stucked pistons throw out by comp. air, cleaning all like a surgeon ina hyperclean area, always new seals and gaskets, if necassary addit new pistons,..and so on,..and as you all wrote before, very important: 
NO any brutal force by throw out, or installing  the pistons, the result of this could made  irreversible damages in the alumium cylinderhousings bore for the pistons!-As ever: Think about before, and acting than!!  )

Thanks for the Kudo Big Joe! I'm a firm believer in some crisp Photos to back-up any text/descriptive hoopla of anything i say. Either makes the medicine go down easier or, sometimes, makes the person inquiring dig into the wallet to sort proper bits. Nessim, as always brought-up an excellent point! Because these rear brake lines run horizonal to the ground/captured by the swingarm, muck will definitely be lodged within the brake line and often plug it up. And..as goes the bore of the caliper so goes the bore of the Master Cylinder. Couldn't count how many of those 5/8 or 14mm i've pitched over the years because of the pitted bores. Yours master cylinder will be a black color. They had two types of those too. Early ones were anodized, later painted If You run into a pickle GD..just give me a ring the ole-fashioned way, telephone!