Seized brake piston?

Okay, this is my first winter with the SV and already the front brakes are binding (badly).

**I swear my ZX6 was never this bad**

Anyway, as you all know I'm a mechanical moron and need some advice.

I've taken the calipers of the the forks and removed the pads to give the whole thing a damn good clean only to discover that one piston in each caliper seems to be solid and refusing to budge!!!!!!

So the questions are this.....

1. How do I free them (to scared to do anything yet in case I damage the rubber seals on the piston)?
&
2. How do I keep them sweet over winter so this doesn't happen again (keeping in mind the bike is not kept in a garage)?

Any suggestions and recommendations are welcome!

Cheers
Richard.

[northwind]

I use compressed air... G-clamp the one that's not stuck, and fire the other out. But you've got to be very careful, they fire out at ridiculous speed (I shot one into the ground from a GSXR caliper, and it stuck about 5 inches deep into the lawn )

Northy that sounds soooooo cool but I forgot to mention that my tool kit is embarrassing and I don't have access to anything remotely like compressed air.

Will blowing through a straw work

Thanks though buddy I appreciate the reply.

[northwind]

Perhaps if you have cast iron lungs

But, easy alternative, you have all the necceary hardware to pressurise a brake caliper- connect it to the braking system, use a wee cheap g-clamp to stop the one that's not stuck from pushing out, and then pump the lever (with no disc in place). Pain in the bum to do, but it usually works. Your dust seals on the stuck pistons are most likely fubared, incidentally, that's how they get stuck in the first place. Main seals might be OK, but it's good practice to replace them in sets whenever you remove your pistons, they say (I don't, never have, I replace them when they're damaged or worn only)

Alternatively, here's one I saw this month in Volksworld- mechanical grease gun. Makes sense, they can apply a huge amount of pressure (that's how they work) though of course it'd fill your caliper with manky grease that you'd need to clean out. I've never done it, but the idea's quite logical.

Originally Posted by northwind

But, easy alternative, you have all the necceary hardware to pressurise a brake caliper- connect it to the braking system, use a wee cheap g-clamp to stop the one that's not stuck from pushing out, and then pump the lever (with no disc in place). Pain in the bum to do, but it usually works.

That's a plan, I'll give it a go tomorrow and let ya know how it goes.

Cheers Northy

What I'd do is put it all back together and bleed it all through. Fork pads removed and calipers not fixed, place and hold a long spanner down inbetween the caliper halves (where the pads sit) so that when the pistons come out, they go so far and then stop as the spanner is in the way. HAVE to ensure they are not going to push the spanner out though so best to do with another person.

I do that because I have no air compressor.

Oooh pretty much what northwind said.

Originally Posted by instigator

What I'd do is put it all back together and bleed it all through. Fork pads removed and calipers not fixed, place and hold a long spanner down inbetween the caliper halves (where the pads sit) so that when the pistons come out, they go so far and then stop as the spanner is in the way. HAVE to ensure they are not going to push the spanner out though so best to do with another person.

I do that because I have no air compressor.

Oooh pretty much what northwind said.

I did it the same way, having no compressor. I found on both mine and my son's that the outer seals had been forced out by a build up of white deposits in the groove, caused I think by salt water penetration. This had caused them to be trapped between the bore and the piston. You need to carfully clean that crap out properly with something pointy (I used a jewellers screwdriver). Some people, including me, use red rubber grease to lube the seals. I find it form a layer on the outside of the outer seals which helps protect it. Some people don't bother but when I've come to service the brakes I've found a red ring of grease when the pistons are pushed out a bit for cleaning, which looks like it's kept the crap from penetrating the seals.

There are people on here with more experience of brakes than I, and no doubt they'll give good advice.

HTH Keith

Keith and Instigator, thank you. That's given me some ideas to get cracking on with.

I'll give those a go today and let ya know how it goes, finger crossed I'll get them shifted.

Cheers
Richard.

Northy, Keith & Instigator, if you guys lived near by I'd buy you a pint.

Clamped the free pistons off and pumped the seized ones through (result).

The dust seals do need replacing but for now I can get back and forward to work without doing rolling burnouts every time I pull the front break

Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you, Thank you.

Rich.

and if you can, you stop them seizing by applying a fair bit of copper grease to the pistons (just avoid the discs!) behind the pads. This will stop them seizing for years, now why they do a half arsed job of it in the factory i'll never know!