Rear caliper locks up ... *sob*

[kar_the_terrible]

So now my rear caliper is locking up. first the mechanic who replaced my tyres forgot to put the floating caliper bolt back on in the rear (and to think he inspected my bike).... so I thought that was what was causing it to lock up.

But after fitting a new bolt, flushing and bleeding the rear brakes it still locks up. Here's what I've done so far:

1) Earlier I put in new caliper seals in both the front and back. Front has a new piston too and works just fine.

2) I had cleaned both calipers to a shiny finish so there is absolutely no corrosion. The rear mast. cylinder piston returns to its original position and fits just fine.

3) I noticed that the rear caliper piston has a super-tiny pit about 0.5mm in dia. otherwise it is smooth and corrosion-free (I can buff it up and see my face in it).

Could this small pit be causing all my problems??? Or is the little spring that pushes the caliper back in faulty?? The folks I've spoken to dont believe that I've bled the system right <hmph> , but I've bled it a zillion times and am confident that Im doing that right.
The thing is that the brakes dont lock up completely either, I can push the bike when in neutral, but it offers some resistance, in fact I can even duck walk it, but I notice the difference. So this heats up the rear disc... and a spit-soaked finger sizzles (not yet bad enough that its red-hot).

Halp!! i need my bike to get around as my car is kaput and in the shop now.

[huh]

if the calipers are rebuilt and workin smooth. then i would go after the rubber brake lines. they can collapse over time or get restricted and not allow the brake fluid/pressure to release. when the brakes get locked up break loose the line at the master cylinder. without pressing the lever and see if it squirts and releases pressure. (like you would with the bleeder screw).
if it does you found your problem

[BuzZz]

It sounds like something binding. If the pads float (no direct experiance with you model) then the pins they float on and the holes in the pad that the pins slide trough must be smooth and clean. Any wear can let things move enough to bind, too.

If the caliper floats, it will have similar pins and holes, but the holes will be in the caliper. Good, high temp grease on these pionts might help.

There, I took my stab at it, let's see if it bleeds......

[kar_the_terrible]

Buzz,
I think the caliper design changed to the kind you're talking about with the 82 model.
In my case there is no continuous pin that aligns both pads. Instead the pads have recesses which slide along guides on the caliper body.

But I get ur point. I'll look at the guides too ... maybe the problem is in there.

[XJRJohn]

just a thought,had a cbx 550 with same prob.started after i serviced the calipers.traced it to a seal that had not seated and was stuck between the piston and the caliper.xjrjohn