Often no parts are needed, the piston will have some corrosion, you will have to decide if it needs replacing.
Cover any nearby paint with rags, plastic. Brake fluid really gets around.
To start loosen master cylinder reservoir cover screws, they are often corroded. Loosen, use a hand impact wrench before you round out the phillips slots, if the screw binds at ALL as you back it out;
stop, spray some lube, tighten back down a bit, now loosen again, repeat as many times as needed to remove the screw,
patience! If all else fails you can drill off the heads remove the cover then you can attempt to remove the remainder by grabbing with a visegrips.
OK back to caliper rebuild..
diagram and photo of the parts
Note: brake cleaner is for
metal parts, do NOT spray, or soak rubber parts in brake cleaner, they will swell and turn to junk.
Crack the brake line banjo bolt, just loose, now retighten, loosen then resnug the bleeder, it's 8mm (Makes it easier to remove these later when the caliper is off the fork.)
If the brake works AT ALL, Do NOT remove the brake line yet!
You do not not need to remove the carrier from the fork tube, the caliper can be unbolted from the carrier and brake pads by removing the bolt at the rh side of the pic above, and the phillips head (JIS #2) screw from the back side. The caliper will now slid up off the brake pads which stay on the carrier tabs.
If you want ot remove the carrier that' fine also. Loosen bolt #6 between two bolts #12 then the remove the 2) bolts #12, remove caliper with carrier from fork tube and rotor.
Rock twist the caliper a bit to help retract the piston to aid removal of caliper. If it 's really stuck a thin pry bar may help, don't abuse the rotor.
Remove screw #5 from back of caliper.
take pictures or notes of where everything fits.
remove bolt #6
The pads will come out, and the caliper separates from the carrier.
Some years have partial shims behind the pads, note position for re-installation.
Pads that have soaked in fork oil are junk and cannot be "cleaned up". Buy new pads.
The pressed steel pad locator you see now that the pads are out, has a prong holding it in, pry back a bit with a screwdriver to release the prong from under the piston on the caliper.
The prong (already released) is seen inside the rubber ring at the top here;
Remove the rubber piston dust cover and it's steel retaining ring. if the dust cover isn't gummy , distorted or torn it usually is reuseable.
Leaky fork seals often swell, ruin the dust cover seal.
Stretched dust cover, this one will not seal well and will let in water/dust, sometimes they get huge.
Here's why you left the brake line attached. Use the handle bar lever and pump the piston out. If it doesn't want to move, it helps to push the piston back in a bit with a large c-clamp, then finish pumping it out. You might need to add fluid to the reservoir. If brake line is already off or pumping doesn't work; put some rag in the gap between the piston and caliper body. This can be dangerous; air line pressure can send that piston into the far shop wall or lop off a wayward finger. Put an air blow gun in the brake line hole give it a
short, light burst of air. piston should pop out. repeat if needed. if it doesn't come right out use the C-clamp, push piston back a bit. try the air again. Really badly stuck pistons can be forced out with a grease gun.
Now sop suck brake fluid out of the reservoir, the caliper, and everywhere else it has gotten to. Remove the brake line from the caliper.
Hint; with the brake line removed from the caliper, brake fluid should dribble from the line until the reservoir is empty. If not you have problems upstream.
Carefully prize out the black rubber seal from the caliper. There
is a bunch of gunk behind it, do not ignore this step. this is why the piston doesn't retract like it should. I like a piece of stiff copper wire bent to a 90 with a square end to scrape out the gunk stuck in there.
The caliper is soft aluminum and can easily be gouged. Check the piston and bore, remove any deposits, decide if you can live with the piston pitting. Minor pitting is usually near the outside where it doesn't affect the seal. If the pitting is extensive replace the piston. Most new ones are now made of stainless steel and should outlive the bike.
If needed use VERY fine paper like 1000 grit or finer, on small piston pits, smooth any rough edges on pits, if needed lightly touch up the caliper bore with the fine paper. clean, dry all parts. Try the piston in the caliper without the seal, it should
easily slide in and out.
Check the slider #7 inside the rubber boot on the caliper, it should push in and out with small effort. if it doesn't, pop the rubber boot #6 from the grooves in the slider and push the pin out, clean and lightly coat with synthetic brake grease. reinstall pin.
Reassemble, wipe a bit of brake fluid on seal, install, use bit of brake fluid on piston, install, push it all the way in. Install the dust cover then the metal ring, use no tools, just your fingers, this may take a few tries to get it right, don't worry the rubber is very tough, repeat til it's in place and smooth.
Old brake lines are crap and need to be replaced. A one piece stainless line is good
Take it to the bank: The master cylinder MUST be completely
overhauled or replaced.
put it all together and bleed per
littlebill's how to thread.
Sorry I just used old parts from the bins for pics.
You don't HAVE TO remove the bracket from the fork leg; caliper can easily be removed from the bracket for pad changes etc. Loosen 1 bolt, 1 screw to remove.
