zxr 750 removing seized pistons from caliper

[royzxr750]

Hi guys iv just taken off my breaks on my zxr 750 to rebuild them as the brakes are crap. well tbh just dont work.Anyways i have split them in half and i can see they been seized and pushed right in for sometime. What i would like to know is wots the best way to get them out or will i be looking at new brakes?

[0ddball]

Piston pliers might work depending on which pistons you have. Some have the pistons with the removable rubber insert, others have the bonded in cork ones.

Best way is find someone with a compressor and a blow gun (or buy one for about £4 from machine mart). Bolt the halves back together and give them 120psi down the fluid hole with a bit of wood between the pistons. When they are all popped out and touching the wood remove the wood and let them come out more till they are touching each other before separating the halves again.
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ZXR750L

[Matt-]

Piston Pliers if possible.

Get them moving, Spray some lubrication in their WD40, then pound some air, go to your local garage and ask if you can borrow their Air line.

Make sure you clean the Pot's up after you have them out
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RIP jack (wheelie king), you will never be forgotten.
Current Bike's - Road Legal TZR 125 Pitbike, Aprilia SR50R 2010

[Mungel]

I learnt this the hard way, like yourself. You need to free the pistons up before you drain the fluid. Once you have split the caliper halves, it becomes far more difficult to free stuck pistons. Compressed air or grease gun will do it, maybe a local garage would help you with this?

When I first rebuilt my tokico 6 pots (good brakes if serviced regularly, don't believe the hype about needing to swap them out), I couldn't remove a couple of stuck pistons and had no access to compressed air or a grease gun, so I put the whole lot back together, using the old fluid, bled the system and then mounted them back on the bike. Without replacing the brake pads, I then carefully pumped the pistons out of the calipers, onto the brake disc. It takes a while and you have to keep the master cylinder topped up whilst doing it.

Once all the pistons are pressed up against the disc, you can remove the calipers and split the halves. With the pistons pumped so far out of the calipers, you can easily remove them.

With everything removed and cleaned up, I personally recommend getting genuine replacement seals as opposed to the cheap ebay copies, but that's merely my preference resulting from a bad experience with cheap seals.

HTH
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Mungel
ZZR600 (dead) - ZX9R (sold) - FZ1S

[gandy666]

I did the same as mungel but took the pads out and put a g clamp on the piston I did NOT want to pop out and that worked.


then i rebled it and moved the clamp to the other piston.

was 2 pot brakes tho, but the principal is the same

[royzxr750]

Right well this evening iv put the calipers back on the bike and bleed the brakes and the pistons in the calipers will not move not even 1mm. So anymore ideas?

[Islander]

Does the lever feel spongy or firm?

[royzxr750]

brake lever feels spongy. Was even like this before i took the calipers off

[Ichy]

Sounds as if you still have air in the system. Try cable ties to hold the lever tight to the bar for a few hours.
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[royzxr750]

No there was no air in the system but tbh i think the seals in the master system are shot

[Fizzer Thou]

When dealing with seized brake calipers I use an old but working master cylinder fitted to an old handlebar clamped in a vice.This is the best way of pushing out caliper pistons.It is a lot easier to sort out one caliper at a time rather than attempting to bleed and sort both simultaneously.
I have a compressor,but using this would not be as effective as pushing out th pistons using hydraulic pressure.I have heard of people using a grease gun to push seized pistons out of calipers,but it does make a hell of a mess once the piston is out and you would need to spend quite some time cleaning it all out.

If you suspect the master cylinder seals as having perished it does not take too much to strip this and at least clean it all up.When I did my one on my Exup recently I found a big glob of congealed brake fluid in the main chamber.The bike has done over 40,000 miles but the seals were still good and the brakes are now as good as.
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Just talk bikes.What else is there?

Always have a 'Plan B'

[Budgetboy]

Poor seals is another one that is often overlooked.These are perishable items and once the fluid starts to go past the main seal that is it.. But the dust seals will hold the fluid in..

If i were you i would bleed the brakes starting from the MC as air tends to get stuck in here. Then bleed your calipers keeping the bleed nipple at the highest point. Once you have done that remove the brake pads & caliper (keep hose attached). Pump pistons out and clean them, dont go to far though (2-3cm normally)
Use red rubber grease and push the pistons back again, remember do one side at a time. push the pistons in and out at least 2-3 times to get the red rubber grease to work.
Replace calipers & pads after that and try the brakes again.
If it still does is move onto the MC.
If you have standard lines check for cracks or damage/getting old.. replace with braided lines.

My guess is it will be air or poor seals.
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[Fizzer Thou]

[Budgetboy]