How to Clean Up Motorcycle Brake Calipers

Cleaning your motorcycle's brake calipers will keep your stops smooth and safe.

Even if you've been diligently replacing brake fluid every year or two, there will come a time when you'll need to disassemble the calipers for a bit of up-close TLC, not the kind they get at the end of the brake-cleaner straw.

Caliper overhaul includes replacing the dust and piston seals, and therefore requires complete disassembly. Don't panic; it's easy. Still, it's worth stopping by your dealer well in advance to purchase the seals, and be sure to ask how many sets you'll need for each caliper. Some manufacturers sell kits that include parts for the piston pairs on each side of the caliper, while others sell them individually by piston. If you're lucky, the dealer will have 'em in stock.

Remove the calipers from the fork legs and disconnect the brake lines. If the lines have been off more than once, order a set of sealing washers; they're about $2 each, and you'll need six or seven for a dual-disc front setup, depending upon how the hoses are arranged. Remember to keep brake fluid away from painted parts.

Remove the brake pads. Before you do anything else, spray the inside of the caliper around the pistons with brake cleaner (1). There's usually lots of junk in there, and you don't want to drag it farther into the caliper as you handle the parts. Blow the caliper dry with compressed air.

Bring the caliper to your bench and place a shop towel or slab of wood between the opposing pistons. Or, if you're working on a single-action caliper like this one, protect the inboard portion of the caliper to prevent damage to the pistons you're about to extract (2). You need not disassemble an opposed-piston caliper unless you suspect leakage between halves of the caliper body; there is a small rubber seal at the fluid passage between the two. Turn the caliper so the pistons face the bench and apply a small amount of compressed air to the inlet port. Do not place the nozzle all the way into the port; leave a little room around the edges (3). The pistons won't need much air to push them out of the bores, and you don't want them flying across the garage.

Typically, one piston pops right out, but the second one might be more difficult. You can grab the piston in your fingers or grip it with smooth-jaw pliers and pull it out of the bore (4). Set the pistons aside and take a good look inside the bores. There will likely be junk in there. Clean them out and look for nicks or gouges that would indicate debris floating around in the system or piston/bore interference. Remove the old seals with your fingernail or (very carefully) a small screwdriver (5), being careful to avoid nicking the bore or the seal groove. Discard the seals; once they're out, they're done.Clean the inside of the piston bores with more brake cleaner and blow out the transfer holes (6). Next, check the pistons' condition. They should be smooth and clean (7). Any surface corrosion should be removed with brake cleaner or a very light application of a ScotchBrite pad. Clean the pistons again and set them aside.

Prepare the new seals with a light coat of fresh brake fluid, then gently insert them into the grooves (8). They're not directional, but as you can see, there are two sets. The inside ring is the actual fluid seal, while the other is a grime wiper; the fluid seal is thicker and smoother. Apply a light coat of brake fluid to the piston and reinstall it with the flat face inward (9); push until bottomed. Clean everything one more time before you replace the pads and reinstall the calipers on the bike.

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