I got a 92' GS500E twin ! i assumed the rear caliper was siezed but after striping it down im not to sure !! i got a bit confuzzled achually :roll: !!
On the caliper only one of the pistons push onto the pads !! the otherone wont move at all !! even when i stripped it down i could not get the other piston to move not even a mm!!! i was just wondering if its ment to move or not ?? i am now assuming its not ment to move !!
(maybe dumb question but i dunno !!! i need a bit of info)
thnks
All the pistons are supposed to move. Mine were stuck too. The manual said to replace them if this happens but after replacing the front ones I decided it wasn't necessary for the back ones. So I just tried real hard to get the stuck ones out- I don't remember how but it probably required some ingenuity. Cleaned them and put some fluid on them and put them back in. If they are stuck, I recommend cleaning the heck out of them and replacing the seals if you can- you probably don't have to replace the pistons unless they are warped and that is what is causing them to be stuck. I also reccomend cleaning all the rear brake stuff (shims etc.- but not the pads) with brake cleaner- I forgot to do it and now my rear ones squeak.
Thanks for reply !
i did clean em and atempted to force the piston to move i think they must be warped ! i will strip it down again tomoro and clean the heck out of it !!! if it dnt wrk then i will just use the good old "adjuster" (which is a hammer) :) show em whos boss :) !! the thing is i need to sort it because only one of the pistons is pushing it is causin the bisc to bend and ware alot quicker !
:roll: but ohwell !! ill live :) just cnt promise my GS will if things carry on going wrong :guns:
Quote from: SlashexeThanks for reply !
i did clean em and atempted to force the piston to move i think they must be warped ! i will strip it down again tomoro and clean the heck out of it !!! if it dnt wrk then i will just use the good old "adjuster" (which is a hammer) :) show em whos boss :) !! the thing is i need to sort it because only one of the pistons is pushing it is causin the bisc to bend and ware alot quicker !
:roll: but ohwell !! ill live :) just cnt promise my GS will if things carry on going wrong :guns:
It isn't that expensive to get a new piston and O-ring set, so I recommend that just to be safe before you try to hammer it into submission. Also, I would feel better if you got a second opinion, besides mine- I've had only limited experience.
Disc brake pistons often stick due to corrosion on the wall of the caliper or piston. There is a discussion thread about the different DOT brake fluids. A couple are hygroscopic - this is they collect water. This is what rusts the caliper and/or piston. Do a search of the forum on "DOT type" to nail this down.
Since this is a '92, you probably don't know the entire service history of the bike. Assume the previous owners were idiots and never changed the fluid and serviced the brakes. If it were me, I would drain the fluid, clean or rebuild as needed. (You do have a Clymer or Haynes manual don't you?) You don't seem afraid to get into it so that is a plus. The calipers I have seen stuck are due to corrosion on the back of the piston. Hammering it won't do because the stuff is behind the piston and you will be putting crap into your fluid. Only draining, disassembly, and rebuilding is the safe thing here. ACHTUNG - Brake fluid is corrosive to most paint and decals. Shouldn't hurt you unless you drink it or get it in your eyes.
Once the brake line is off and the caliper is on the bench (or garage floor as needed), you can use a compressor to "blow" the piston out. CAUTION - put something a little less than the thickness of the rotor between the pads before trying this. I have a t-shirt with black speckles all over it because one piston shot out of the caliper like a rocket when it let loose. Also cover the entire mess up with a rag to catch splatter. At least the stuff washed off my face. Press the rubber end of a blow attachment to the hole for the banjo bolt. GENTLY squeeze the blow handle. Practice this before hand.
On that same caliper I had one piston totally siezed in. Ended up cutting a slot in the piston and using some steel to twist the sucker loose. Ugly job. Ended up replacing the piston anyway due to rust/corrosion.
If one is sticking, the other may not be far behind. Running it on one piston does more than wear the pad crooked, it cuts your clamping pressure in half. You may not think you notice it, but it is less than before. For casual braking it would take an accelerometer feeding a PC to show it to you. Hard braking would definitely get your attention. :o
Make them both work. They should work smoothly.