I have a 1983 CB650SC, why are the brake calipers locking up?

Question

It started over the weekend. Brake calipers locked up on the rotor. You could not move the bike forward or back. I had to pop the bleeders lose and wedge a s***w driver in them to pop them loose. Once home I could take them apart and clean them. There was a build up of material from years of use. However, the indicator on the brake pads still shows good? So, at this point I am stumped... I rode the bike to work today and the same thing happened again?

Answer 1

It could be 1 of 2 things; both can create this and since your brakes can lock up, can be dangerous.

1) if you have moisture in hydraulics, it will heat up right away causing

    the brakes to lock (While using them, not while just driving)

2) The little cyclinders themselves can have a edge worn between

    themselves and/or the pistons. In either case couls cause this

    to jam in the forward position.

This is assuming that the break lever or pedal is returning. You can also have a bad cyclinder at  the lever. That would be easier to tell.

get it fixed asap as it can be dangerous.

Last , the indicator is just how much pad you have left/.

Answer 2

it's none of these answers... given the year of the bike you probably have the brake line to the caliper collapsing internally...you can't tell by looking at it!...if you opened the bleeder and were able to move the piston the caliper is free... which leads to the brake line as being the problem....

Answer 3

More than likely you have worn the brake pads down to the metal which caused the caliper pistons to become to hot damaging the piston rubber seals. Re-build the calipers.

Answer 4

I just did this repair over the weekend.

The brake calipers need to be rebuilt.

Gunk builds up under the seals, making the seals squeeze tighter against the pistons, preventing them from returning on their own.

Also after years of use, without cleaning them, the pistons get dirty and rusted on their exposed surfaces, making them even more difficult to return.

Replace the caliper pistons and seals.

Clean the piston cylinders with a caliper hone (aprox $25).

Using a pick, scrape all the junk out of the seal grooves.

Answer 5

Rebuild the calipers, when you take the piston seals out clean the gunk out of that groove (this is your problem), get new seals and reinstall them with a little brake fluid, bleed and test.

Next time they lock, smack the caliper with a plastic/rubber mallet if you need to move the bike, but don't ride like that fix the caliper right away.

Answer 6

its either the calipers need stripping and cleaning to remove the build up of grime  that is preventing the pistons from  returning properly.You will need a caliper rebuild kit - seals and dust seal and possibly new pistons if the  current ones are very rusty and pitted.

Or it could be the wrong  or mixed brake fluid