Boxerworks.com

Tim Shepherd wrote:If the front brake lever is frozen, either the master is rusted solid, or the cable is, or both. See if you can get enough slack in the cable to remove it, by turning the adjustment things at both end of the cable and see if you can lever the end of the cable off the actuating arm of the master cylinder. Then, if it still won't move, cut the cable as close to the grip to remove and grease all pivots and reassemble with a new cable.

There's always the simple rusted frozen lever pivot, but I assume you'd be able to figure that out just by the feel: absolutely no movement of any kind.

Major Softie wrote: There's always the simple rusted frozen lever pivot, but I assume you'd be able to figure that out just by the feel: absolutely no movement of any kind.

Yeah, the brake lever is just like the clutch lever on a R90. That leaves the cable to the master cylinder, the master cylinder itself, and possibly a frozen up caliper.

I think it would be relatively easy to figure out which. I would take the tank off the bike and do some evaluation. I would pull the rubber boot off the rear of the master cylinder, which will give access to the master cylinder mounted lever. By loosening the adjuster nut on the brake cable it should be readily apparent if the cable is moving freely or is frozen up. If it were the cable, which I doubt, cutting the cable with an angle grinder would allow a new cable to be installed.

I would expect the master cylinder to be the culprit. That could be easily evaluated by attempting to move that little lever on the master cylinder. A long screwdriver or board could be used as a lever to see if the M/C lever is free or not. Or maybe a pair of vice grips fastened tightly to the M/C lever. The point is that the master cylinder piston will be free to move or not move. I expect that the piston is stuck. It's in a nasty environment, particularly if the master cylinder has been weeping some fluid past the piston.

If the piston is frozen up, then the master cylinder should be taken off the bike. I would then mount the master cylinder in a vice, butt end up, and then use a phillips screw driver and hammer to see if the piston itself can be made to move with some judicious taps of the hammer. If it does move then you stand a chance of prying the circlip out and removing the piston from the master cylinder. Then some honing of the bore with wet or dry sandpaper or cloth backed sandpaper in a slotted stick and some soapy water will reveal the condition of the bore. If the piston was stuck, though, I would expect the bore to be badly pitted as well.

If it wasn't the cable, or the master cylinder, then it has to be the brake caliper that is frozen up. I don't have any experience disassembling the swinging ATE caliper, but if it's stuck I suspect it will be toast. I have heard of making a zerk fitting adapter to screw into the brake hose inlet, and then use the pressure of a grease gun to pop the caliper piston out. I don't know what holds the caliper piston in, but I'm guessing a circlip type of retainer.



Ken

The caliper piston is held in by friction. A good blast of pressure will pop it out, provided the disc/pad(s) are not there, AND its not frozen.

I can't remember the rule for apostrophes with the it word.

Don't fret, "it" can be hard. (like it has... - can that even be "contracted???")

it's = it is
its = POSSESSIVE

Yeah, caliper disassembly is done by blowing the piston out with compressed air. If he removes the line and rebuilds the caliper and as well "knows" the locked brake lever is not due to a cable (if there is one on those) or seized lever itself, with the brake line open at the wheel with the front caliper removed, if grabbing the brake lever and squeezing does not yield a mess of fluid all over the floor out of the line to the caliper - the master cylinder's piston is surely what has seized.

A word of caution with blowing out the caliper piston with air; you can lose fingers easily that way. You need to put progressively thinner and thinner pieces of "something hard" (we used to use hunks of different thickness cut off discs we had welded handles on as this procedure was being done many, many times a day/hour...) Blow the caliper piston out a bit at a time until you are down to removing the last "spacer." At that point, BE CERTAIN not only that no body parts are between the piston and the other side of the caliper, but as well, be certain TO COVER THE CALIPER WITH A RAG, for DOT 3 brake fluid is no fun in the eyes - and it WILL come blowing out as a mist everywhere when the piston comes out... Actually, depending on if you have the correct sort of attachment to blow air into the fluid hole, COVER THE CALIPER EVERY TIME YOU BLOW AIR INTO IT, as fluid will blow back out of the entry hole every time too...

Native /5 wrote:I can't remember the rule for apostrophes with the it word.

its (posessive) - its piston
it's (it is) - it's not frozen
"it" girl -

I had "it" all correct above - missed "IT" being Clara Bow though...

Somewhat shocking I might have forgotten about 'IT' - She DID have 'IT.' That is, until she lost 'IT' all...