Scooterotica

Is there a way I can free-up a seized piston, on the grimeca disc brake?

Presume its a two opposed piston type? If its still plumbed in, clamp the other piston and work the lever, you may get movement/lucky.
For use off the bike, I adapted an HD grease gun to take a flexible brake hose. Basically the same deal, clamp the free side, and pump away.
If you use this method, I would replace the seals, which you may have to do whatever way you get it out.
Any hydro-carbon oil, grease or anti-seize fluid will be absorbed into the rubber and sooner or later the seal will fail.
The seals do the work of retracting the pistons too, by gripping the piston. As the pressure moves the piston outwards, the seal deforms. Release the pressure and the seal pulls the piston back. As the pad wears the piston moves beyond the point which the seal can grip, the seal slides back to position it is comfy with. Then release the pressure the piston will retract not quite so much - voila! self adjusting brakes.
Sorry to ramble, but that is why you should not put any lube on the seal. Or lavish copperslip on the pads, because it then gets on dust seal and rots that, water gets in, well you know whats going to happen then.
I use a very thin smear of copperslip on the pad, and a smidge of high temp silicone grease (from a plasma cutting torch) under the dust shield.

djh66 wrote:Is there a way I can free-up a seized piston, on the grimeca disc brake?

air line with a rubber tipped blow gun stuff it in the banjo bolt hole an ya can blast the piston out a da calipa and clear da length of an average garage; I did that; maybe wrap the caliper in a dust sheet first,

muppet,

Thanks for the advice, I will try as soon as I get chance.

Would you beleive it, I've now misplaced the c-clip from the caliper pin, searched all over the bloody garage
Does anyone know what size in mm it is?