Classic Motorcycle Build

Harley Dual Disc Caliper Rebuild (1977-1983)

Article by Vintage Vinny

Rebuilding brake calipers is usually less expensive than replacing them, plus it keeps the bike more original. This article covers rebuilding Harley dual disc brake calipers 1977 through 1983.

Harley dual front caliper rebuild 78

First seen on the 1977 XLCR Cafe Racer and FXS Low Rider, Harley dual disc brakes were standard equipment on 1979 through 1983 Sportsters, 1980 through 1983 FLHT models, and several FX models (Wide Glide, Fat Bob, and Low Rider). Although most were chrome polished, some models had calipers finished in black.

Harley FX dual front caliper rebuild 78

Looking through old Harley parts books, it appears that 1977 through 1983 Harley dual calipers are interchangeable, but the right caliper only fits the right side, and the left caliper only fits the left side. Internal parts are the same for either side.

Rebuild or Replace Calipers?

Most, but not all, motorcycle brake calipers can be rebuilt. There are three reasons why calipers would not be rebuildable:

The caliper housing is cracked. This could happen if the bike was in an accident, or through damage.

Rebuild kits are not available. This is never a problem with classic Harley motorcycles. Rebuild kits are available from dozens of aftermarket suppliers.

The piston bores are too badly damaged. A badly pitted piston bore may cause a piston to stick, but corrosion is usually not an issue with aluminum-bodied calipers.

If you have a slight amount of pitting on the piston bore surface, it can often be sanded or honed out, but if there are any deep nicks or grooves, it's best to replace the caliper.


After sitting idle for several years, both front calipers on this 1981 Sportster had frozen up. There were two options; rebuild them or replace them.

repair or replace Harley brake calipers

After checking to see what replacements would cost, the decision was made to rebuild the old ones.

NOTE: If only one caliper is frozen or leaking brake fluid, it's advisable to rebuild or replace both sides. If you find that only one is rebuildable, it's OK to rebuild that one and replace the other one.


What's Involved

A brake caliper rebuild will involve removing, disassembling, cleaning, and then reassembling the caliper with new seals. On older bikes that have sat for awhile, the piston may need to be polished, and the piston bore may have to be honed. You may also have trouble removing a stuck piston.

Parts Needed

If needed, caliper seal kits can be purchased online.

Harley dual caliper rebuild kit

Shop: Harley Dual Disc Seal Kit

The original Harley caliper rebuild kits had part numbers 44151-77 and 44153-77. Each caliper requires one seal and one dust boot. Aftermarket kits usually service one caliper only.

If the brake pads were contaminated by leaking fork oil, or had brake fluid on them, or just worn out, replace them.

Harley dual caliper rebuild kit

Shop: Harley Caliper Rebuild Kit


Other Parts Needed

You won't know what else you'll need until the calipers are off and disassembled. On a 40+ year-old caliper, you'll often need to replace other parts, such as a caliper piston, caliper pins, or a stripped bleeder screw.

Tools and Supplies Needed

Tools needed include a 3/8" drive socket set, open and closed end wrenches, and Allen keys or sockets. You may also need a brake caliper honing tool if the piston bore is badly corroded.

Flare nut wrenches, also called line wrenches, are designed to remove steel brake lines and other hydraulic fittings without damaging the nut. A standard wrench will work, but you stand a chance of stripping the fitting.

You'll also need a can or two of brake parts cleaner, some DOT 5 brake fluid, and shop towels or rags.

NOTE: It's not necessary to remove the front wheel to remove the calipers.


Before Removing The Calipers

Spray the mounting bolts, bleeder screws, and brake line fittings with WD-40 or similar penetrant. The longer you allow the penetrant to soak, the better it will work (overnight is best).

It's usually easier to loosen the bleeder valves while the caliper is still mounted to the fork. Once loosened, tighten them up by hand so they don't leak while taking the caliper off.

1981 Harley caliper rebuild

Some brake fluid may come out of the brake hoses after they're disconnected from the calipers. Have a piece of cardboard underneath to catch any overflow and brake fluid.

mounting bolts for Harley dual disc calipers

Remove the mounting bolts, washers, and locknuts (one long, one short per side).

caliper rebuild Harley 79

Once the center caliper bolt is loosened, the outer and inner halves should easily separate.

rebuild Harley caliper 80

Spray/clean all parts with brake cleaner.

rebuild Harley caliper 78

Remove all dirt, rust, abrasives and old brake fluid. Dry with compressed air.


Removing a Frozen Caliper Piston

Even with 100 psi of compressed air this piston would not budge!

stuck caliper piston removal

Read: Remove Stuck Brake Piston


Removing a Stuck Bleeder Screw

On one of the calipers, the bleeder screw head was stripped. To remove, the caliper was placed in a vice between two soft jaw pads. Once securely in place, penetrating fluid was sprayed on and left to soak for a few minutes.

soft jaw pads for workbench vice

Bleeder screw removal was now easy with a 1/4" drive 6-point deep socket.

motorcycle caliper bleeder screws

Above: old and new bleeder screw.


Brake Caliper Inspection

Once the piston was unstuck, all metal parts were cleaned with brake parts cleaner and shop towels, then blow-dried with compressed air.

Harley caliper rebuild 83

With a flat-blade screwdriver, lightly scrape out any corrosion out of the grooves where the caliper O-ring will seat.

Harley dual brake caliper rebuild

After cleaning, run a fingernail inside the bore and check for any nicks or grooves.

Brake Caliper Honing

brake caliper hone tool

A rusty or pitted piston bore can often be renewed with a brake caliper honing tool and a hand-held electric drill.

brake caliper honing tool

Caution: Be sure you are using a brake caliper hone with 1000 grit stones. Do not use a small engine honing tool that looks the same, but has 220 grit stones, as it would take off too much metal and leave a rough finish.

Another way to hone a caliper bore is by hand. Start with a medium grit, then switch to fine, and finish with 600 or 1000 grit.


Brake Caliper Piston Polishing

One of the easier ways to polish a brake caliper piston is to chuck it in a lathe or a drill press at low speed.

sanding brake caliper piston in drill press

After removing a few nicks with 100 grit sandpaper, I switched to medium and then fine Emory cloth, then finished with 1000 grit sandpaper. The piston was then cleaned with brake parts cleaner and blow-dried.

rebuild Harley dual calipers 77

After honing, wipe out the cylinder and clean off the stones. Look inside the cylinders and see if all pits and corrosion are gone.

Repeat the honing process until the bore is smooth and free of scratches. When done, wash out the bore with soap and water to remove all traces of the hone grit, then blow dry with compressed air.

The brake caliper is now ready to be re-assembled.


Coat the new O-ring seal, new piston boot, and piston in DOT 5 brake fluid. The O-ring gets installed first, then the dust boot.

Harley dual caliper rebuild kit

With everything still lubricated with brake fluid, push the piston though the dust boot and O-ring, and into the bore.

Caliper assembly procedure is: inner plate, brake pad inner, brake pad outer, and then outer plate.

Harley caliper rebuild

Left and right calipers have identical brake pads, assembly plates, and pins.

Harley caliper pins 44162-77

The old caliper pins had a little corrosion on them, and were sanded smooth with Emory cloth. If your caliper pins need replacement, their part number is 44162-77.

The caliper bolt (with flat washer) is torqued to 60 to 65 foot/pounds.

Sportster caliper rebuild


Replacement Dual Calipers

1977 through 1983 Harley dual calipers are not that common, and if you can't rebuild yours, finding good used ones won't be easy. And remember that the two sides don't interchange - right calipers fit right-side only and left calipers fit left-side only.

The last solution is also the most expensive. If your old calipers cannot be rebuilt, and you can't find a good used pair, you can buy replacement calipers.

Harley Sportster dual front caliper rebuild


Related Articles:

Remove Stuck Brake Piston
Best Thread Sealant For Brake Fittings
Commando Brake Caliper Overhaul
Sportster caliper rebuild

Read: 1973-1977 Harley Caliper Rebuild