Help Help! Stuck pistons in disc brakes!

Okay, nearly have the carbs figured out... and now pushing the bike back in the garage, MAN! The pistons in the disc brake calipers are stuck tight!

I pulled the calipers off, and used brake-fluid pressure to get one side about half way out... and then realized that if I popped the pistons out, I could never get the other side caliper loose.

Anybody have experience with this? How to rebuild the calipers? Is there a link to a thread that I can find? Sorry to sound so desperate... any help would be more than appreciated.

 

OK, so not a huge problem. There are probably going to be lots of other suggestions, but here is what I have done in this situation.
Get a pair of "C" shaped vise grips. They are great for working on brakes.
Use the vise grips to hold one piston in place, then use the fluid pressure to pop the other piston. Once it is out, you will need to split the caliper and rebuild that side.
Once that has been done, you will need to re-assemble the caliper, bleed it, and use the vise grips to hold the rebuilt piston in place, and repeat the process on the other side.

Also check this. Good info http://xjbikes.com/Forums/viewtopic/t=1 ... liper.html

Hope that helps..

 

Compressed air is another option, but you had to watch out as the piston will go flying as soon as it is loose. My front brakes were so incredibly gummed up that just about nothing would get the calipers or anti-dive pistons loose (put your bike in you sig ChicoJim). What worked for me is getting an 8mm grease fitting from Autozone, and hooking up a hand pump grease gun. Popped all but one of the antidives right out. It makes a big mess to clean out of the caliper, so have plenty (read 4 cans if you have anti-dive) of brake cleaner available so make sure you clean every bit of grease out before you reassemble. This was suggested in one of the other threads **edit-it was suggested in the link above**

 

+1 for grease gun. cleanup is not nearly as bad as some would suggest. The upside is a safe, smooth release of the piston (regardless how bad it's stuck), with virtually zero effort and no collateral damage.

P.S... the grease gun tip fits perfectly onto the bleeder valve... So all you really need is a 10x1.25mm bolt to plug off the banjo side of the caliper.

 

I used compressed air because I didn't want to deal with grease clean-up, but as man said, be careful as the pistons do come out with force. I placed a shop rag between the two to capture the piston.

Brake fluid gets gummy over time, so what you are seeing is normal for a bike that has been sitting for some time.

You can get rebuild kits. What I did was to completely clean the calipers and pistons. You will need a needle point scraping tool to get all of it out of the grooves. Make sure the pistons are shiny and clean before you attempt to put them back in. I treated the piston o-ring with some silicone grease before install to make sure it was pliable. Once you get everything cleaned up, the pistons will slide in and out as expected.

It's not too difficult of a job. The hardest thing is getting the pistons unstuck. After that, it is just the time to get everything clean. Take your time and make sure you get all of the old gunk out.

 

I used compressed air from a small pump (like you might have to inflate a tire in the back of your car that plugs into the ciglighter). It cam out no problem nor did it go flying across the room. Clean and smooth. Replace the rubber bits. Re-assemble and with braided lines and a MC rebuild, bike now actually stops well.

 

+2 for grease gun. It will work when compressed air gives up. No down side. As far as mess, no problem. We are dealing with an old brake system. Everything is a mess.

 

THANK YOU ALL! WOW! This is so cool. I'll post an update once the stoppage has been restored to the ol' FJ600.