caliper/piston problem

[LarryC]

I've done a search which brings up dozens of threads none of which (of those I sampled) contained info of any use. So: the piston(s) in my front calipers are seemingly fixed in place. I've tried vise grips- no didn't lock em, just grabbed hold. No movement I could detect. No rotation or anything. Surely they must move in order to do what they do. What is the secret?

I bought this bike with the front brakes not working. The PO had worked on them- the fluid was drained. I need to go through it to make sure all is well.

[Agemax]

compressed air through the banjo bolt hole. aim it into a bunch of rags or the mother in law

[pete]

compressed air through the banjo bolt hole. aim it into a bunch of rags or the mother in law

That's gold right there! I call mine the "outlaws"...

I ended up having to use a pipe wrench on mine, compressed air wouldn't even budge it.

If you resort to that, you will need a new piston set because the jaws will bugger it up.

Also check the cylinder very carefully to make sure everything is clean, serviceable, and in spec.

[Indysteve]

Yep, I had to do the same with a pair of channel locks.
Buggered up the piston good, but after about 20 minutes they finally came out, and surprisingly the walls were clean and not scored.

My guess is you have clogged passages so most likely you will find a bunch of old crusty dried brake fluid.

[Rover]

Have you tried this: With the caliper hooked up to the master cylinder but without the rotor in the way apply the brake,if your system is not too buggered you may be able to pop them out.

[cowboyup3371]

I used a couple of flat bladed screwdrivers to pull my piston out. Remember, new kits will include a piston as well.

[LarryC]

Yeah I considered reassembling the whole thing and forcing it out hydraulically. That would test the master cylinder too. But it is so rigidly in place I thought it must be fastened somehow. Unfortunately I don't have certain things. Like a vice. Or a pipewrench. Or even channel-locks.

[Adler]

Yeah I considered reassembling the whole thing and forcing it out hydraulically. That would test the master cylinder too. But it is so rigidly in place I thought it must be fastened somehow. Unfortunately I don't have certain things. Like a vice. Or a pipewrench. Or even channel-locks.

In my experience, popping them out hydraulically is the least destructive way to pop out the piston without a compressor. If the return port on the master is blocked you will have some trouble popping them out that way. I say rebuild the master cylinder then use it pop out the piston.

[LarryC]

Ya know I forgot to ask. Why...or how is the piston jammed in there anyway? Corrosion? It swelled up? Seems it should be fine forever except for corrosion- if the materials are compatible and don't bind. The weak point should be the rubber seals. Thats how my Honda was anyway.

[Nessism]

Corrosion mostly.

These photos are typical of what you find inside the calipers after poor maintenance.

[pete]

Yup, they do tend to get crappy with neglect... I neglected mine for the best part of 10 years while it sat... I have a new master cylinder from Mikes XS and I just did the new piston etc. in the caliper:

[LarryC]

Wow those do look bad! I don't see any trace of that kinda thing in mine. Old fluid was discolored a bit but no solid matter. Looking in thru the banjo bolt hole looks clean too. Nevertheless they are locked in place.
That last pic- number 7. Is that the inside of the cylinder? I saw that view before but thought it was the piston. Not like mine! So I bought another caliper on ebay lol. (I have the N model- only one front caliper)

[pete]

Nup, that's the piston, it's hollow in the centre. I have no idea why though... maybe for weight or something?