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Author Topic: Brakes heating up and locking up ruined the caliper and disk?  (Read 766 times)

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Offline cb750fbomb

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Brakes heating up and locking up ruined the caliper and disk?
« on: July 02, 2009, 05:36:55 PM »
I have another post about my brakes locking up, http://forums.sohc4.net/index.php?topic=54020.msg580204#msg580204. It is started happening and then started happening more frequently. The first day I noticed this happening all the fluid seemingly boiled out of the caliper. So, I have a buddy that builds custom bikes out of Triumphs, SX650s, early CB750s and sometimes Harleys and he grew up on bikes. He knows more about bikes than maybe anyone I know, besides the nice folks on this forum, and he swears that since the rear caliper has heated up and locked up that the caliper is shot and the disk is likely warped. He told me that I'm wasting my time replacing the inner seal and I need to get a new/used caliper and a disk. Anyone have any input on this? I'm about to install the rear caliper after soaking it in simple green and scrubbing filth out of it. All the parts except the inner seal seem fine and the caliper and piston are clean. The piston has some rust pitting inside that indention, towards the end that touches the pad and a couple of tiny nicks on the flat end. Sorry so long winded and thanks  :)
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'77 CB750F2
“The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.”

Offline Toxic

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Re: Brakes heating up and locking up ruined the caliper and disk?
« Reply #1 on: July 02, 2009, 05:49:24 PM »
ummm  I think your buddy knows less than you give him credit for.

You prpbably need new pads.

Warped rotor maybe, due to massive heat, sure that is a possibility.  But it is easy to detect a warped rotor.

The caliper is not likely to be damaged.

Post some pics of the parts and there are lots of people on hear that can advise.

Sounds like your knowledgeable buddy hasn't even seen the parts so how is able to make such a blanket statement like that?  Maybe he has parts to sell you.
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patrickd

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Re: Brakes heating up and locking up ruined the caliper and disk?
« Reply #2 on: July 02, 2009, 06:09:00 PM »
There is nothing that can go wrong with these calipers with the exception of a type of gunk that builds up under the D-ring that seals the piston. This buildup does not allow the piston to retract back into the bore and the pads drag. I bet you could turn that rotor on a lathe and retrue it. Don't buy into needing a new one till you take it to a brake shop and have it turned.
Take the caliper apart. remove the piston and the O-ring. Don't cut the rubber o-ring. Clean the slot in the caliper the ring rests in real good with a small wire brush. Completely clean it up in solvent, dry it super dry so as not to contaminate the new fluid. Reassemble with new pads and fluid and I bet you'll be good as new.
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Offline BeSeeingYou

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Re: Brakes heating up and locking up ruined the caliper and disk?
« Reply #3 on: July 02, 2009, 06:20:26 PM »
 Some pitting on the piston is ok and fairly common..  They don't have to be pristine.  Will the piston slip in and out of the caliper without the seal in place?  It should just by it's own weight.  With the seal in place it will take quite a bit of force to push it in.  If thats the case I would give it a shot.  I don't remember if you have the F1 or 2 but either way that rear caliper can be hard to come by.  Not impossible by any means but they both only had two year runs.
« Last Edit: July 02, 2009, 06:23:53 PM by srust58 »
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Offline cb750fbomb

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Re: Brakes heating up and locking up ruined the caliper and disk?
« Reply #4 on: July 02, 2009, 07:41:24 PM »
Everyone gives him too much credit because he's a builder and I was thinking he was full of it. He couldn't get my bike runnin' a few months back but Spanner1 and I got it going. I did an ass load of research and got it closer by myself than he did. The guy doesn't know crap about PD carbs, for example, but he has seen a lot more bikes than I have 'cause this is my first bike. I have a tendency to listen to people that have more experience than I do, but with him I've started taking what he says with a grain of salt. He also doesn't have any parts for my bike he's trying to sell me, so that's not his angle.

Got the caliper back together and pushing the break pedal barely moves the piston. The inside of the caliper is clean enough to eat off of. I just got off the phone with Spanner1 and he told me to try to clean out one of the holes in the reservoir. The same one that apparently a few people have had clogging problems with from my research. I also need a break bleeder and my bleeder valve is rounded off and rusted up badly. I'm going to try using a screw/bolt extractor and then I guess I'll have to go buy a propane torch if that doesn't work. I've also got 3 Speed Bleeder valves on the way.
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'77 CB750F2
“The major difference between a thing that might go wrong and a thing that cannot possibly go wrong is that when a thing that cannot possibly go wrong goes wrong it usually turns out to be impossible to get at or repair.”
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