Topic: Stuck caliper pistons

[Scott S]

 It seems like good working brake calipers are one of the hardest things to find for these old bikes, especially the 500/550's.

  I've been watching ebay, etc. and the prices that stuck or frozen calipers are bringing is outlandish.
  I have at least three in my parts pile that are frozen solid. I've tried nearly everything....heat, PB Blaster, compressed air, BFH, etc. I can't even get the pad out of a couple of them!

 It's been suggested that I use grease. Can anyone show me how to make a fitting to pump them full of grease and push the piston out? Pics? Parts list and where you buy the fitting(s)?

 I just have a small grease gun in the garage.....do I need to find a shop that has one of those big, air compressor powered grease guns?

 And on that note, I'm really surpised that someone hasn't come up with a suitable alternative caliper. There are dozens and dozens of calipers out there that ought to work with a modified  or scratch built bracket, etc.

[Teatimetim]

honestly, any vehical that sits to long is going to have that problem.  Mine has sat for 17 years so it should be interestesting to get to working.

[fmctm1sw]

I've never failed to pop them out with a good master cylinder.

[knowsnothing]

I've never failed to pop them out with a good master cylinder.

+10

Scott, i have had 3 that have had stuck pistons.  The grease gun work on 2 of them pretty easily (i have a small one too), but the 3rd one was a bastard.  Not only was the piston stuck, but the pad and rusted and gotten its self stuck as well.  I tried just about everything (heat, pb blaster, BFGs, grease gun) to get that one out and nothing worked. 

I had a spare master laying around and figured what the hell, so i hooked it up, filled the reservoir and start pumping it like it owed me money.  The  lever got really firm, but i kept squeezing and to my surprise i heard something move a little and then the damn thing popped out.  VICTORY!!  it only took about a year.......

[Scott S]

 The ones I have left all have the pad rusted in place, too.

 Has NOBODY figured out a different caliper to use?

[MCRider]

In my case, I had the pump type grease gun with the short rubber hose. I unthreaded the end from the hose, leaving a short male thread. I threaded this directly into the caliper. It is NOT the same thread so don't force it, but it will catch a few threads. That was all i needed to gently pump out a stuck piston, otherwise unmovable.

It was very easy, took only a few moments compared to hours unsuccessfully trying other things.

Worst part was cleaning out the grease. 

[Mainerider]

I've found that compressed air works best and is very clean to use. With the bleeder valve in, insert a well-fitting nozzle into the brakeline hole, cover the caliper with a towel and blow around 90 lbs pressure in. Invariably the piston pops out within a few seconds. It does pop out with force so watch your face and cover it up so it doesn't fly out.

[Scott S]

 Tried that already. I need some SERIOUS force.

[Mainerider]

Are you using a nozzle that fits snugly in the banjo bolt hole? I've had some very badly pitted  pistons still come out easily. If its truly that pitted, galled and/or rusted in it may not be  not worth salvaging.

[sir funk]

It's been suggested that I use grease. Can anyone show me how to make a fitting to pump them full of grease and push the piston out? Pics? Parts list and where you buy the fitting(s)?

 I just have a small grease gun in the garage.....do I need to find a shop that has one of those big, air compressor powered grease guns?

I used a 10mm grease fitting I bought in a assorted metric pack at pepboys -- http://www.pepboys.com/product/details/9169087/.  It threaded right into the caliper where the brake line threads in.  Threaded it  in, made sure the bleed screw was tight, and started pumping.  Came out in about a minute or so. Grease gets all over;  make sure you remove the seal to clean it up and clean the grease out of the holes running to the bleed screw and brake line.

[MCRider]

Tried that already. I need some SERIOUS force.

Air or grease?

The grease is much more controllable and the pump gun applies an amazing amount of force in a controllable way.

You may need to get the fitting Sir Funk speaks of, but it wasn't necessary for me.

[70CB750]

I used grease gun on two and it worked both times. Not even an adapter, just press the gun to the open bleeder and start pumping. The bleeder is close enough to zerk to make it work.

[camelman]

Tried that already. I need some SERIOUS force.

Then use the stock master cylinder. With your 14mm master cylinder piston, a 10:1 brake lever ratio and a 150 pound squeeze, you should get almost 5000 pounds of force on the brake pad. It will push your rusty brake pad out.

Camelman

[Eydugstr]

I've never failed to pop them out with a good master cylinder.

+1.  Nothing against the idea of using a grease gun, but I use a m/c on a set of old handlebars in a vise,  and then set the caliper in a coffee can or a kitty litter tub.

[Scott S]

I used a 10mm grease fitting I bought in a assorted metric pack at pepboys -- http://www.pepboys.com/product/details/9169087/.  It threaded right into the caliper where the brake line threads in.  Threaded it  in, made sure the bleed screw was tight, and started pumping.  Came out in about a minute or so. Grease gets all over;  make sure you remove the seal to clean it up and clean the grease out of the holes running to the bleed screw and brake line.

 Perfect! Only $4.99 for the multi-pack and I got all three calipers apart! They all look rebuildable, too. Pistons look OK. One bleeder may need repair.
 Other than that, this pile of junk parts is now usable and actually worth a few bucks!

[mrrch]

Pics are excellent!
I've used this method a couple of times with sucess.