SOHC.co.uk Forums > CB350/400
Seized brake piston
McCabe-Thiele (Ted):
--- Quote from: K2-K6 on November 26, 2021, 05:18:14 PM ---They can get hellishly tight and need alot of effort to initiate moving, as you're finding.
When like that, probably only the hydraulic system will move it with the leverage needed. The mastercylinder will generate into the hundreds psi wise.
You could try putting a spacer onto the piston and squeezing in a vice to see if you can crack the corrosion sealing it seized, then see if it'll pump out. Sounds counter intuitive, but once moved from fully stuck they'll usually get going.
--- End quote ---
The above suggested method has worked for me in the past - for stubborn ones in the past I used an old MIni Clutch Master cylinder to pump the pistons out.
PaulC:
--- Quote from: K2-K6 on November 26, 2021, 05:18:14 PM ---They can get hellishly tight and need alot of effort to initiate moving, as you're finding.
When like that, probably only the hydraulic system will move it with the leverage needed. The mastercylinder will generate into the hundreds psi wise.
You could try putting a spacer onto the piston and squeezing in a vice to see if you can crack the corrosion sealing it seized, then see if it'll pump out. Sounds counter intuitive, but once moved from fully stuck they'll usually get going.
--- End quote ---
Thanks K2 I'll have ago at that tomorrow. Would using heat help?
K2-K6:
Heat almost certainly won't hinder it and may benefit, there's not much risk and I'd be inclined to heat the caliper in an oven rather than direct with heat scource.
There's essentially nothing inside them, just the piston and seal and they're pretty robust anyway.
Bryanj:
Ive never had the grease gun fail, but then i do use the air one at work, also you can get a caliper complete with with mounting, bolts, adjuster and pads from amazon for about £66. Put cb 500 caliper into the amazon search but scroll down as there are several and prices vary a lot, if you leave out the bracket i saw one at £51
PaulC:
--- Quote from: K2-K6 on November 26, 2021, 06:57:48 PM ---Heat almost certainly won't hinder it and may benefit, there's not much risk and I'd be inclined to heat the caliper in an oven rather than direct with heat scource.
There's essentially nothing inside them, just the piston and seal and they're pretty robust anyway.
--- End quote ---
Best wait until the wife goes to work for that one 😉
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