Caliper Caper

[Myumi-2]

The front brake caliper in my 1972 CB750 is not disengaging fully and makes a squeal as I ride.  

I plan to remove it and free it up.

Is there a standard solution to this problem?

Do I just remove it and force the caliper in and out till it frees?

What do I use as a lubricant?

Are there any other potential causes for this problem, i.e. master cylinder?

Cheers
Tim

[Tech78]

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[gonebiking-2]

The caliper must be stripped down and cleaned out. Use a very fine wet & dry sanding paper ( 800 -1200 grade ) and clean out the pistons. Replace the seals and then re-assemble. The reason you are getting the aqueal is that the disc pads are not freeing themselves from the disc and are constantly rubbing lightly against the disc. Their could be a certain amount of moisture in the brake fluid which might have caused a little bit of corrosion that needs to be cleaned out. Once this has been done and you get fresh brake fluid in the line etc the ptoblem will go away. I drain and flush my front brake every year so that this problem does not happen

[Myumi-2]

How do you remove the cylinder from the caliper unit???

[Polymer-2]

Stuff some rags in there to cushion the piston then blow some air into the brake line inlet and it'll blow the piston out.. Keep your fingers out of the way and wear safety goggles!

[sr58]

Use the master cylinder to force the piston out.  It is a lot safer than using compressed air.  The piston seal stretches a tiny amount and this pulls the piston back when you let off the brake lever.  Put in a new seal and make sure you clean out the groove that it sits in.

[Rick V]

 The other source of a sticky caliper on the early bikes is the pivot on the plate that the caliper mounts to. Be sure that it pivots freely. When you reinstall the caliper it is important to adjust the clearance between the inside brake pad and the rotor. To do this you loosen the lock nut on the adjuster screw and adjust the screw until a .003 inch feeler gauge just slides between the inner pad and the rotor,tighten the nut. If this is not adjusted you could have the pads still dragging or if the clearance is too high the brake lever will have too much travel.

[Myumi-2]

Thanks for that.

With a cost of a few dollars I got a nnew square cut seal from my friendly Honda dealer.

I used compressed air to blow out the cylinder.  The master cylinder was not able to push it out.  And it took a little while with the compressed air to push it out.

The old seal seemed in pretty good condition but came out easily.

The unit was not that dirty on the inside.  A bit of grit on the cylinder that was all.  I used a fine steel wool to shine it up again.  Same for the caliper.

I put it back together last night with the new seal and all the problems seem resolved.  The brakes go on and come off.

Thankyou.