Brake caliper stuck.

[Magua]

I've been putting my brother's bike back together (gn250). Renegade master and I attached the new (from a wrecker) brake caliper and bled the brakes.

Unfortunately the piston has pressed against the pads, but wont retract. So while faulty, I can't remove it to exchange for a working specimen.

Any tips on removing it?

[imdying]

Lever it off carefully. Either that or beat fuck out of it with a hammer, shouldn't take long. You really should service any caliper that's been off a bike for a while, they tend to corrode up. Any calipers I have in storage, have been totally stripped down and wrapped in grease paper. Sucks to come back to an otherwise good caliper and find the pistons have light pitting in the chrome (which makes them throwaway).

[riffer]

Once you've got those pads levered back you'll need to clean up the caliper. Remove the caliper.

Basically, you need to push the pistons out. You will need the following ingredients:

1. A pair of locking mole grips.
2. An air compressor with air gun attachment.
3. An old rag.
4. Some brake fluid.

Place the rag over the end of the piston on one side of the caliper and place the molegrips over them and lock tight. The rag is to stop the molegrips from putting dents into the piston.

Place the air gun over the bit where the brake hose goes into the caliper and blow air into it - really hard.

The piston will go "POW" and come straight out.

Now search in the gargre for the piston - they can really fly out some times.

PLEASE don't put your finger in the way. It really fucking hurts.

Now you need to put this piston back in the caliper. Not all the way. You want to still be able to get it out again. Use liberal amounts of brake fluid to clean the piston a bit. I use Autosol to polish the piston but that can come later. Use the rag and molegrips to hold the piston so it has a good 7mm sticking out.

Then push out the other piston with the airgun. If you've greased the other piston enough you should be able to pull it out. Failing that, grease up the piston that's out and you'll gradually get them both out.

Do you know how to clean and/or replace the piston and seals?

[Magua]

Do you know how to clean and/or replace the piston and seals?

I do not. I shall try to aquire an air gun and mole grips and will get back to you.

[scracha]

If you've got a sliding caliper as opposed to opposing pistons, then the air-gun method is a pain in the arse, especially if you ain't got all the fittings. Also more likely to fark up the seals.

To get it off the brake disk, just lever the pads against one another with a couple of flat screwdrivers.

Once the caliper is off the disk, pop the piston(s) using the brake lever. If there's multiple pistons then pump them out one at a time (using hand pressure or g-clamp on the other piston(s) to stop them all coming out) Clean out the piston and the bore that's left behind (stating obvious but be gentle). If the piston is farked then you've no alternative but to get another. I use a tiny bit of silkolene high melting point grease on my brake pistons but some folks say you should just use brake fluid (I dunno, it's never caused problems for me), should go back in with hand pressure only but if all else fails use g-clamps.

Lazy men pump the pistons out a centimetre or so and clean them, pop back in with g-clamp, and repeat a couple of times up but if the piston is sticking real bad then it's likely to be crud behind the seal so you've no alternative but to pop the piston(s) right out.

Be gentle putting pistons back in otherwise you'll fark the seals. Take for test ride when finished as nothing more scary than unexpected failed brake seal.

Oh..and you haven't overfilled the brake fluid eh?

[FROSTY:Me]

or just bring the whole plot to me and Ill sort it for ya

[owner]

I thought the recent thread about the YZF brake rebuild was an excellent ,easy to follow, "real world" description of everything that is needed to rebuild brakes, If you haven't read that, its worth a gander. Or if the GN has a completely different setup just take it to Frosty he'll sort it!!!!

[scracha]

If you haven't read that, its worth a gander. Or if the GN has a completely different setup just take it to Frosty he'll sort it!!!!

I'd imagine a ginny has a cheapo 1 piston sliding caliper setup which is a piece of piss to do. Although way more efficient, opposed pistons are a PITA if they're stuck.

[imdying]

I use a tiny bit of silkolene high melting point grease on my brake pistons but some folks say you should just use brake fluid (I dunno, it's never caused problems for me), should go back in with hand pressure only but if all else fails use g-clamps.

Some folks are right then... this is the brake equivalent to shaking a baby.


Never use petroleum based products on your brakes.
Never use G clamps to push a piston back.

[scracha]

Some folks are right then... this is the brake equivalent to shaking a baby.
Never use petroleum based products on your brakes.
Never use G clamps to push a piston back.

'Scuse my ignorance but can I ask why?

[motorbyclist]

I thought the recent thread about the YZF brake rebuild was an excellent ,easy to follow, "real world" description of everything that is needed to rebuild brakes, If you haven't read that, its worth a gander. Or if the GN has a completely different setup just take it to Frosty he'll sort it!!!!

i was thinking the same thing

of course squiggles could give a hand being a GN expert

and i'm not doing much these days...

I'd imagine a ginny has a cheapo 1 piston sliding caliper setup which is a piece of piss to do. Although way more efficient, opposed pistons are a PITA if they're stuck.

nah the YZ didn't have opposed, but in my piston cleaning experience a collection of metal spacers (often incl. the pads) is great for stopping 3 of four pistons moving

'Scuse my ignorance but can I ask why?

cause you're forcing things, which usually breaks things - they should go in easy unless something is wrong and you don't want to take a chunk out of the seals or the caliper itself

of course this is the difference between "how you should do it" and "how you do do it"

[Magua]

I got the piston out, it was pretty dirty, as was the bore. Trouble is I can't get the damn thing back in, pretty tempted to use some grips, heh.

[FROSTY:Me]

duder --call MCC--they are on here come see me lets sort it out --all will be fine

[XRKID]

I got the piston out, it was pretty dirty, as was the bore. Trouble is I can't get the damn thing back in, pretty tempted to use some grips, heh.

Like i told you befor use special honda tool #001 and #002 hammer and skewdriver (flat) it solves everything, beleive me lol. CRC works wonders too air compressers and special tools are for people with lots of money and no musscle. lol JJ gud luck

PS. Dont let ya mates use the skewdriver and hammer while you are holding the object, you end up bleading alot

[motorbyclist]

don't use crc on or near the brake seals

just dont