Repair of motorcycle brake calipers
Motorcycle Operation

Repair of motorcycle brake calipers

Restoration of calipers, seals, piston, rear and front brake rods

6 Kawasaki ZX636R 2002 Sport Model Restoration Saga: Episode 25

The braking system is complex between hoses, calipers, pistons, seals and a braking system that requires bleeding. Clamps are particularly vulnerable and require either a complete refurbishment or replacement of the seal. In our case, they really need a lot of renovation.

Of course, in order to touch the caliper seals, said brake calipers must be disassembled and open in half. Provided that this is possible, of course. That owners of monoblock calipers keep a hacksaw ...

Front brake calipers

It's up to you how you want to start loosening them: mount or break the fork once (more difficult). This is the easy part, especially since I don't need a workshop stand to do this! So, I bring the Tokico goats home. After fully halving, I remove the pistons, which I pull from the inside so as not to damage their polished surface. It is durable, but still and above all the piston, it is not given: you have to count from 10 to 30 euros (per unit!) Depending on the model. So we go there with tweezers, literally and figuratively.

On the Kawasaki 636, not all pistons are delivered the same, which confirms the relevance of replacing their seals. Therefore, I am even more willing to remove worn out joints. There are two of them per piston.

Motorcycle brake caliper seals: old left, new right

One for sealing, a spinner, the other for protection, acting as a dust cover / scraper. He cleans the plunger before entering his house. Every joint is bleeding. They are easy to distinguish: they do not have the same thickness. However, they can be renumbered. Therefore attention is required.

Then I transfer the body from the caliper to the cleaner brakeseven if the exterior is frankly good inside. I disassemble the bleed screw and check the condition of the seal and the screw itself. Apparently everything is in order. After completing this step, I replace the seals and then coat them with the lubricant provided (some soak them in brake fluid before installing, I don’t need to do this) before reassembling the pistons. They are all in good condition and will not need to be replaced either. Now everything glides perfectly and very gently and smoothly. It promises!

I take the opportunity to change the spacers. Since the axle was not very formed (corroded and heavily oxidized), I ordered two on my last visit to Accessoirement, while returning the old ones with silicon strips, just in case. So I have everything I need.

Rear brake calipers

This operation is done on the front brake calipers, I am doing the same for the rear caliper. If it only has one piston, the principle is identical. On the other hand, there are some variations and different parts. Indeed, the caliper slides along the center of the support and provides the best braking performance. Thus, there are two axles, which are themselves protected by bellows and fixed to the plate. I'm going to dismantle it all.

After cleaning, I realize that the brake fluid is dark in color: it is in poor condition.

Cleaning the rear brake calipers

The hose is disconnected, I return the caliper to the operating table after placing it in the water and cleaning it. It's always nicer!

Rear brake caliper disassembled and flushed

Unlike the front calipers, it does not need to be opened: it is one-piece. Disassembly, on the other hand, is more difficult (without being complicated) in the sense that more parts are scattered: support, bellows, gasket spring, gasket holding rod and their pin, and gaskets. This is followed by the piston and its internal push pad, not to mention the two seals: the two-lip dust cap and the seal itself.

Many parts make up the brake calipers

The gasket rod is in poor condition, but it can be repaired thanks to the polishing wheel, my magic tool par excellence.

Polishing the cleaning pad rod

The gaskets are not very worn out and look nice, which is a great point. You don't need to change them. The same applies to the axle bellows. The original is also thicker and offers more spring than the replacement, which is why I prefer it over the repair kit.

If the pad spring is not visible in any way, I tug on it and restore the shine before proceeding to remove the piston.

Extraction of the piston on the WD40

It costs a little effort and reveals the bottom of the bowl with a lot of dirt. Therefore, disassembly is useful. So much the better. I clean everything up, remodel the seal seats and get the stirrups like new. It remains only to return to all this!

Dirty brake caliper piston

The piston, even when cleaned, is quilted and is no longer as smooth as it should be: protruding metal chips. This can damage the joints. I decided to polish the surface to smooth out any roughness before reassembling it.

The mission of grain sandpaper 1000+ soapy water is accomplished, it has regained its appearance and baby skin.

Cleaning the piston and repairing the rear brake calipers

Replacing seals in the brake caliper

I put the piston seals in their housing and grease before putting the piston back in place. It resists profusely and preys on air, which is a sign of a good seal. I clean the sliding axles of the bearings and check their appearance and wear. I lubricate them and return one of the bellows (the one that is clamped in its housing before securing the support).

Hind leg as good as new!

The gaskets are, of course, reinserted and put into action using a piston from which it only exceeds about 2 mm. The axis of the pads is flawless. Everything is fine. I have a smile to get the task done and without error or surprise.

The complete refurbishment still took me almost 2 hours. Result? Aromum like new! All you have to do is pick it up and push. Be careful to push the piston back onto the disc after pumping properly. The same goes for the front brake: it would be a shame to be in the wall for not thinking about strength testing in the presence ...

Everything is flawless

Remember

  • Replacing the caliper seals means restoring all stopping power and all original power.
  • Be careful not to damage the surface of the pistons when trying to pull them out of their housing.

Not to do

  • Too much stuffed into the pistons before disassembling them! If they are reluctant to come out, we will have to find a way to push them back. It's not always easy.
  • Tighten the gaskets too tight, pushing the pistons away if they are not on the disc.

Tools:

  • Key for socket and socket 6 hollow panels

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