Seized brake pistons

I'm currently having the heads worked on on my xj750r and I started working on my front brakes (hoses, pads, general inspection) and I hit a problem I can't get the pistons out to re build them any hints or ideas or solutions?

 

Close the banjo-bolt hole with a regular bolt. Open the bleed nipple and fit a grease gun to it. Fill it with grease until the piston pops out. Be sure to wrap the busines end of the caliper with a heavy rag to contain the mess and prevent the piston from getting damaged when it pops out.

 

can you use air to pop them out k-moe?
just asking.

 

According to the manual I downloaded it says use air but I don't have an air compressor bike is stored in an unheated garague so I'm hoping they are just frozen right now. What is the best way to clean out all the grease?

 

Compressed air won't do any good on a stuck caliper piston. It only works on one that's not stuck. The brake fluid already in there will keep most of the grease from sticking. After the piston pops out the grease will come out in one blob. Any good brake cleaner will get the rest out.

 

Yes you can use air, but the pistons can be too far stuck for that to work.

 

If you use air be sure to put something on the piston to protect it with it pops out--'cause it comes out with a lot of force. I used air and clamped the calipers together and used a piece of inner tube to block off one side of the caliper so that only one piston would be forced out. I then took some doubled up inner tube and put it between the piston and the other side of the caliper to protect both the caliper and piston. It's slow but it worked for me.

 

You could always remove the caliper from the rotor and pump the brake lever, you may need to top off the MC doing this and should have a pail to catch the brake fluid when the piston comes out.

Although it sounds like you already have it off the bike. . . . Next time try the above.

 

If they are cold that could be part of the problem. I like to warm them up with a heat gun and use the grease gun method. They don't need to be hot just warm to the touch.

 

Lots of great ideas thanks everyone, I'll let you know which method works once I get around to it

 

Just chiming in as I had this problem last summer with two of my bikes and I did a friends brakes on his Maxim as well. I wasn't able to get a grease nipple/gun to fit the bleeder properly, and couldn't find a grease nipple that would fit properly into the bleeder screw tapped hole.

Here is what worked;

Top up your brake fluid reservoir and bleed the brake line. If you have it apart, put it back together again and bleed it.

How do y0u bleed it you may ask? Top up the reservoir with brake fluid, pump the lever and hold it down. With your other hand, loosen the bleeder screw on the caliper until some brake fluid comes out (typically a spurt of air comes with it when you first start). Once you have it so that only brake fluid comes out (no air spurting), it's bled.

Keep it all hooked up, lines on and bled...note again, the line must be bled otherwise you are just squeezing air and won't have the pressure to loosen the pistons.

Loosen the caliper and lift (with effort if they are stuck) the caliper off of the disc. You may have to pry a bit, don't wreck anything.

Leave the brake shoes in place and pump the brake lever. One of the pistons will move before the other, don't let it come out on it's own otherwise you'll never get the other piston out, stop it with a piece of wood between the shoes on that side. Keep pumping the brake until the really stuck one comes loose.

It uses quite a bit of brake fluid, you may have to keep an eye on the reservoir and keep it topped up and ... did I mention bled yet.

Once you get them out, you can clean everything up. There will be some white junk, dark goo and other crud in there. remove the seals, they come out much bigger than they went in, and it feels next to impossible to get the new seals in as they look way too big, but they eventually go in with a lot of fiddling.

Good luck

Gord

 

I coat the piston/seal with Kroil (soaked q-tip to get it evenly coated around the piston).
Then tighten a metal band clamp around the piston (hopefully you have a quarter-inch or more protruding) above the caliper body.
Never had a scratched piston (used this technique four times).
Preheat the oven to 425-450 degrees. Then put the caliper in, bake for 20-25 min.
I was pleased to not stench-out the kitchen, helps to do this in warm weather, so the room can be aired out, if you live w/ someone who might object.
Take it out and put an ice cube in the piston. If it doesn't pop and sizzle the caliper isn't warm enough.
Grab the band clamp adjuster with a pair of pliers and rotate the piston. Add more Kroil if necessary.
Rotate the piston while pulling upward and spirally withdraw the piston from the caliper. Sorry, don't have any pictures.

 

Never had one that wouldn't come out with the grease gun. I wouldn't use compressed air--- that's a HUGE-guage shotgun waiting to happen, and you sure don't want to be in front of THAT When it pops..... Cuz it'll be behind you before you even realize it went THROUGH you

 

Hogfiddles is right. No compressed air, Although not as bad as going through you, I know one guy who badly crushed a finger tip when the piston came zipping out.

I could never find the right fitting for a grease gun, maybe it's the metric/sae thing...

 

My greasegun fits right onto the bleeder

 

Sounds like an interesting idea however my wife will probly object to baking my calipers at 425 for 15 min. Let cool on cookie tray and enjoy ha ha

 

+1 on the grease gun. I just had to take apart two front calipers from an XS1100 that sat for 18 years, popped right out. Cleaned, made a split mandrel out of some 1/4" round stock, used that in a drill with some 400 grit wet or dry and WD40, and the bore looked like new. The pistons I polished on a buffing wheel setup. Those are replaceable for not much money if they are too far gone.

 

I tried the compressed air and it would not budge my pistons. You could probably safely use compressed air, just stick something where the pads go so the piston cannot come all the way out, like a small piece of 1X wood...

 

I just did this yesterday. I tried the grease gun but the bleeder was not correctly fitting to the grease gun. I used the short hose that goes from the MC to thensure splitter, hooked it directly to the caliper. It took some bleeding and lots of pumping but the pressure built quickly and didn't need that much fluid because of the short hose. I dangled a five gallon bucket off the handle bars and let the caliper hang inside. The piston popped out easily though you have to line it up with the opening on the other side, it can hang there. After a DreMel and brake cleaner rinse, threw the new seals and pistons in, then the nightmare of bleeding the system started... finally got it tonight.

 

I got one piston out by bleeding and pumping but forgot to stop it before I had the other side completely out but it came out easy with a few blasts of air I have a lot of cleaning before putting it back together with new seals, the slide rod where the boots are was stuck pretty good so I've got to clean that and order my new parts and I should be good to begin the painful bleeding process again