KMX200 Brake Rear Caliper

[Zedxfarin]

In the next few days lads i'm going to be taking apart and rebuilding the rear brake caliper from my kmx200. The caliper is seised at the moment but i'm hoping the piston will be reusable. I am also going to be fitting it with new pads.

Never worked on brakes like this before, I have only ever bled the brakes. Any dos or donts for me before taking on the job. thx
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Montesa Cota 350cc, Yamaha DTr 125cc, Yamaha Timberwolf 250cc, Yamaha YZ 250cc, Kawaski kmx 125cc, Kawaski kmx 200cc, Yamaha TY80cc, 175cc Chinese Dirt Bike, Chinese Wanyge 125cc, Mini & Midi Moto 50cc - What i have owned.

[DrDonnyBrago]

[Teflon-Mike]

HOW To: Overhaul a Brake Calliper / Replace Calliper Seals & Brake Pads

Should give you some insight.

I'd plan on replacing the piston. If the seals are shot, but the piston OK, it would leak, not sieze. Only reason it'd sieze is corrossion between piston & caliper body, exposed piston almost always the worst effected, especially as that has the precission ground sealing surface.

There's two types of piston, chromed and stainless. Chromed, often get the messier as the chrome will flake off when they get corroded. Stainless often look like they aren't so bad & might polish up, but infortunately, they are often as bad or worse, the corrossion leaving bad surface pitting.

Also if the pistons siezed, they are a pain to get out, and it'll almost be garanteed you'll have to resort to tugging it out with grips, buggering the sealing surface.

Face it; if the pressure in the hydraulics from the master cylinder aren't enough to shift it, then compressed air wont do much, and the liklihood of getting it out OK with a pair of piston grips that expand inside the piston and dont grip the sealing face is boarder-line.

And if you dont have any of that kind of specialist kit on hand; then its £15 or so against the inevitability it'll need changing anyway, and the hassle and cost of running round garages & M/C shops asking them to try and pull it for you, before you find out, tyou need one anyway!
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[Vincent]

Get the caliper off and, with the piston facing down, pour some plus gas around the edge of the piston, where the seal is. Let this soak in for as long as poss, pref over night or even longer, then use the brake lever to pop it out.
Never use any grips to get it out you'll f**k it up fer sure.

Carefully clean out the grooves where the seal/seals sit/s and cover the new ones in brake fluid before sticking them in.

As Teflon says, if the piston has anything but perfectly smooth sides, there's a good chance it'll leak.

[Zedxfarin]

I got the caliper off today. The pads are a mess thay have big chunks out of the side of them. I took the caliper off before i read your replys. I hope the piston will shift with air, I will soke the piston in petrol. I'm looking at replacing the piston and seals.
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Montesa Cota 350cc, Yamaha DTr 125cc, Yamaha Timberwolf 250cc, Yamaha YZ 250cc, Kawaski kmx 125cc, Kawaski kmx 200cc, Yamaha TY80cc, 175cc Chinese Dirt Bike, Chinese Wanyge 125cc, Mini & Midi Moto 50cc - What i have owned.