piston stuck in caliper (brakes)

[flumpy7]

Hi all

Prob been asked a million times. Need to do a caliper overhaul on my vt500ef. Pumped out one piston with the fluid i.e pumping with no pads in place. The other is stuck, really f*ck$n stuck.

I haven't got any compressed air before anyone asks, tried using a footpump but just not happening. The caliper is currently disconnected. Any ideas anyone?
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2012 Sinnis apache

[andym]

reconnect it with 1 pipe if possible, top up brake fluid and pump away...

If the air didn't work and the fluid doesn't work try taking it to a local tyre fitter and see if they would give it a blast for you... or petrol station tyre pump

[janner_10]

You could try slotting the removed piston back into the caliper and clamping it in its fully retracted position, use a flat bit of wood. Then refill the system with fluid and try and pump the stubborn one out by using the brake lever / pedal.
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Yamaha FZS600 (Now gone to heaven) > CBR600F4i (SOLD) > '99 YZF-R1

[HD]

Yeah get the system back to how it was and keep the piston that works back and pump the other out. You may need to bleed the system a bit to get the pressure to pump it out.
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Rusty '02 Vito Camper + CBR600F3

[flumpy7]

[HD]

If it is bled properly then you would hope straight away if all of the other pistons are held back. When you are trying to bleed the calliper, it may try to edge out anyway. Make sure to stop it before it falls out cos else you wont get the others out. I like to get all 4 out slightly, then split the calliper and pull them out. If I can't pull them by hand I put a bit of rag on some mole grips and give it a firm tug.
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Rusty '02 Vito Camper + CBR600F3

[flumpy7]

[HD]

You 100% it doesn't split as the rear on my Derbi was a tiny 2-pot and that did? And yeah clamping it down with something usually works, like mole grips again, best tool for doing brakes haha! And its not that hard to pull them out sometimes, other times like this you've got no hope
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Rusty '02 Vito Camper + CBR600F3

[janner_10]

I had the same on my fazer rear brake - one of the pistons wouldn't budge so I split the caliper and manhandled it with a pair of mole grips as a last resort - It didn't mean a new piston though, but I knew this.

Turned out the seals on the rear master cylinder were on their way out so it couldn't build the pressure up to free it. Thankfully found a recon one for £12.

If you cant shift your stuck piston with fluid alone it maybe worth splitting and trying grips and be prepared to replace said piston and seals as they are easy to damage.
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Yamaha FZS600 (Now gone to heaven) > CBR600F4i (SOLD) > '99 YZF-R1

[Budgetboy]

As others have said connect the brakes up again and use fluid.. But heres a little tip..
Get a pick and pull out the old dust seal if you can before you connect the brakes back up.
if you are rebuilding them you wont mind ruining the seal,just go steady.
there will be less resistance on the piston then.
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www.Mailorderrepairs.co.uk We service your Carburetor's, Calipers & Suspension for less Also Bike repairs undertaken.

[steven_191]

If you do use grips to pull it then be careful and make sure you don't leave any burrs. This may fuck up the new seals.

There are pullers but not sure how effective it would be considering how stuck it is.

Also you could try attaching it to a bigger master cylinder to get more power through the line ie the front master cylinder.

[Vincent]

The problem is that you're looking up how to do this after and not before attempting the job. If you had looked before, you'd have seen that you shouldn't pop out the loosest piston until the other one has started to move. So you apply pressure, then when the first piston starts to move, stick a block of wood or something on top of the piston to stop it moving any further. Apply pressure again and the other one will pop out.
You need to reinstall the removed piston, bleed the system and try again. Make sure the seal is good on the re-installed piston.
You could see how much a new piston is, they vary in price depending on how they're made. If it's cheap, pull yours out with a pair of mole-grips and replace with a new one. I have a front wheel off one of these in the lock up. Is the caliper inside the disc cowl?
Not much help I know but you might remember to look fist next time
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Space Is Deep

[andym]

You can try this at your own risk... I don't know if anyone has suggested it, but with the caliper off, if you can get a screwdriver down into the back of the piston, you can try that with some gentle pressure just to get it moving slightly then try the air again.

I had to do this with my intruder brakes, OK it scratched the back of the piston slightly, but it got it to start moving then air took care of the rest... but as I say that is at your own risk. I'm guessing the piston on mine just had so much crap in there because it didn't have a dust seal it had locked the piston.

[flumpy7]

[andym]

Might sound stupid, but if you have the new piston and seals, if there is anything left of the piston sticking out can't you just get a good grip with (and I had to look online for these, still not sure if it's the right name though) waterpump pliers and twist the piston out? it doesn't really matter what state the piston is in if you have a replacement.

Normally I would have said use the handle of a hammer and tap the piston back into place (I've done it with old and new seals in place), but if it's pissin' fluid then it sounds like you've messed something up around the nipple.

[flumpy7]

[bikenut]

hi dude,

reassemble so u can use hydraulic pressure, place caliper in hot water and pump away..........or use heat gun and pump away........some pics and results would be good.

[bagger]

ive done this loads just use a big rawlbolt m25 size or so put in the piston tighten down till it grips then use molegrips on the side of the bolt and turn and pull
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sv650s,cb350s

[Vincent]

[Kickstart]

Hi

As others have said, reassemble, bleed and pump the pistons out, blocking them so they both come out together.

If the bleed nipple is not sealing then you have a bigger problem, as that is only an issue if the bleed nipple is tightened up. If it is leaking when tightened up then the caliper needs some work (ie, possibly drill out the bleed nipple and cut a thread for the next size up, but take care that it will still seal) or better being replaced.

[Stonefly]

[Kickstart]

Hi

You have just made me think. Some ZZR600s have plastic stuffers that can be easily removed while others have the odd ones moulded into the pistons.

As to removing them, not sure. You probably can get away with it. However I suspect the main purpose of them is to insulate the calipers (and the fluid) from much of the heat generated in the pads. Remove them and the fluid will probably get a bit hotter. Also they are slightly proud of the pistons, so without them the pistons will need to come out slightly further for the pads to contact with the disks. Doubt by a critical amount but just something to be aware of.

All the best

Keith
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