revenge of the calipers

[5hort5]

Ok, the front calipers came off fine and the pins weren't stuck but I want to get one of the pistons out of one as it's stuck and pliers don't move it. I have pushed another piston in and attached the caliper to the rear break line and filled with fluid again but I'm not getting a presure to push out the stuck piston or the other one for that matter.

The setup:

Pot of brake fluid, bled system, no air coming out but also no pressure or resistance on the rear pedal.

To bleed the system I open the bleed nipple when pushing down the pedal, held the pedal down and closed off the nipple before letting the pedal up, I now just have fluid going through.

What am I doing wrong?

http://i132.photobucket.com/albums/q37/5hort5/cal2.jpg

[fastdruid]

Ok so first I wouldn't have used pliers on the pistons unless you are going to replace them, too easy to damage them.

What you need to do now is to remove all air from it which is most likely hiding behind the piston, close the nipple, lube both pistons with red-rubber grease and use (ideally) a brake piston compressor, (in reality either a G-clamp or I use water-pump pliers with a rag to prevent damage to the caliper body) to push the piston all the way in while holding the caliper so the pistons are pointing downwards (so you are pushing them UP).

If you have an 'S' make sure that you don't have an air-lock in the hose from the res to the master cylinder, open it up and squeeze the tube between them, if you get air bubbles then you have, either give the tube a few squeezes inbetween pumps of the lever or move the res so the hose is vertical.

Then pump the lever and see if it moves the pistons, if so then put something in the way to prevent one pistons popping out while the other doesn't move (I use a spanner), then pump until all pistons are touching, remove and you should either be able to remove by hand or a few extra pumps should pop them out (watch out for the fluid spillage!
If not then it needs more bleeding but there should be no space for the air to go.

Druid

[5hort5]

Thanks druid, that worked a treat. looking at them I'm not the first one to have a go at em with a pair of pliers, I'll clean them up and post a pic of them latter to see what you think.

thanks again - si

[5hort5]

mmm, two are fine with no marks, the one I had a problem with is on the right and the one on the left was like that on the bike. What do you think?

http://i132.photobucket.com/albums/q37/5hort5/piston.jpg

[fastdruid]

I personally would swap those, certainly would the one on the left, the one on the right isn't too bad. You could get away with them though.

http://www.wemoto.com/bikes/Suzuki/SV_650_K1_K2_X_Y/99-02/picture/Stainless_Steel_Piston_and_Seals_Front_Caliper/

Druid

[Biker Biggles]

As you have taken the trouble to get them out Id change them.They will probably work OK but will always be open to collecting crud and corroding where they are damaged and will be loads of trouble over time.

[thefallenangel]

can see where the one on the right has seated itself. the mark all the way around has suggested it's stuck there. I would say they are okay to reuse providing you keep an eye and clean out twice a year. But it's up to you and money dictates these things.

[flymo]

they are fine, I've used worse than that on a race bike. If you have any deep plier marks at the very tops of the pistons then you can lightly (very lightly) smooth them over with a flat needle file and/or some fine wet/dry paper. Anything further down the piston that will come into contact with the brake fluid seal will need replacing.

You can measure the depth of the cylinder that the pistons fit into and determine the position of the fluid seal (its the deepest of the two seals) then compare that to the piston. Anything above that depth cannot come into contact with the fluid seal and so should not cause any fluid or pressure loss.

[hardhat_harry]

Look ok but if you are going to use pliers always stick a bit a rag between the pliers and piston so the pliers dont mark them