Front Disk Brake Rebuild

The restrictor 'valve' is a jam fit in the spring and both should just fall out of the bore or come out pulling on the spring some. If not then likely rust has jammed em and likely pitted bore to resleeve to recover. May try putting in boiling water to expand the alloy and try to extract, otherwise run a screw in to pull out as trashed internals anyway. Could buy a whole 'nother fork and gear and be done with Norton all together but factory brake is easy enough to make work quite well enough to squeal ABS like at hwy speed then worry about letting up lever grip not to lock up as speed bleeds. In a panic crisis there's some safety against adrenalized grip taking ya out before stopping upright. I absolutely hate when I have to let off brake an instant to recover grip and reapply as lose some bike lengths of stoppage. '72 Trixie's poked out valve with new rubber hose and cleaned up rotor has made me swear off common recommendation of 100 front tire instead of my usual 110 as my 2000 mile old 100 is wearing out the center first rather than the sides and just can't take my sense of urgency of slowing needs I'm used too. SS hose will add a bit more security of transferring fear reaction into tire reaction and RGM race lever takes a bit less grip effort to do so too. I never EVER trail brake unless going so slow hardly need to anyway, so all my real braking is done bolt upright with both tires in line, then let off to actually lean and turn, usually with some power to help by then.

I tried drilling out valve but the rubber just expanded around drill so hole closed back up too much, then tired red hot 6 penny nail to get clean hole joy. [no sex jokes please] Spoke with Mark Davis on his 850 @ LOP Texas, that tried hot nail method a year ago and said its still working its treat with nil planning ahead as prior and about 1/3 shorter stoppage w/o panic grip as prior.

Lockheed has ~17:1 ratio, 1/2"-13mm bore gives ~19:1, 12 mm ~21:1 while moderns are in 22-25:1 range.

A wellworking disc brake starts with the proper ratio of caliper piston to master cylinder piston size. Hoses, pads, rotors, levers, all contribute to a brake's efficacy, but having the right ratio is, by far, the biggest factor to brake performance.

kernel65 said:

And if I don't have air, do I really want to go prying or sticking a pick into the those areas?

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Scott, I don't think you have a straight shot at the bore through the brake light sender hole or the hose to the caliper. They're angled down. Besides, like you said you could scratch the bore. Maybe something like the tube from a can of carb cleaner or brake cleaner. Anything plastic and flexible. If that fails, take the M/C the the gas station and go at it.

P.S. Just about any auto repair shop would have an air nozzle with a rubber fitting on the end to get just the kind of seal this needs. Make sure they have the master cylinder pointed at something that will catch the parts when they fly out of there like a shot.

kernel65 » Tue Oct 08, 2013 4:47 pm
Any trick to getting #11 and #12 out of the reservoir?

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Ugh, thot ya just teasing. I've done 2 mastercylinders, both rusted swollen pistons to a fault, one that had eaten into the bore, but both allowed all the guts to spill out, after the rather stuck pistons with rust embedded decayed seals extracted. Make sure the spring and valve are really in there first. #12 is the spring, so if the little plastic spreader #13 came out then a screw chould be worked into the open end of the spring to tug it out w/o touching the bore with the screw, though what the spring drags out with it may. If spring comes out leaving the rubber restrictor valve behind with its hard plastic 'bobbin', I'd try to sheet rock screw the bobbin out and on into the rubber valve's hole and try pull it too. Would take a big blast of air to shock it out as has a bleed hole not much air pressure can build up otherwise. A drill press-mill with flat faced bit a bit smaller than bore could be run in to clean out the bottom area which don't need nor want any sealing, which is reason to open/remove the restriction anyway. The 3 bore areas that matter is the section the two piston seals work on and the outer low pressure seal at the lever end. If no joy then its trashed anyway so send as a core to the resleever who will just make a new bore removing what ever in the way. I guess if ya'd got to it 15 min sooner ya could of saved it...