Norton Commando Workshop Manual

## Brakes, Weels and Tyres

# H

Master Cylinder Overhaul
Prior to commencing work on the master cylinder it is desirable to obtain a supply of new Lockheed Series 329 Fluid in a sealed container. Where supplies are unobtainable and the fluid may have to be re-used, it is suggested that fluid is collected in a clean jar or receptacle by means of a short length of clean rubber tubing from the bleed screw to the collecting jar. Release the caliper bleed screw one full turn and operate the hand brake lever a number of times until the master cylinder reservoir is empty. Close the bleed screw and detach the drain tube. Store the collecting jar safely and cover carefully to prevent dirt ingress.
Master Cylinder Removal
1 | Disconnect the brake stop light pressure switch spade terminals and lift away the plastic switch cover exposing the hose union into the master cylinder.
2 | Detach the hose from the master cylinder.
3 | Remove the four switch casting screws and lift away the master cylinder complete.

Master Cylinder Dismantling - See Fig. H16
1 | Remove the reservoir cap and bellows seal.
2 | Remove the brake light pressure switch.
3 | Remove the pivot bolt locknut and withdraw the pivot bolt and lever.
4 | Carefully prise the boot circlip from the lower end of the master cylinder. This can be achieved if care is taken to lift three or four adjacent segments progressively, a little at a time until the circlip is tipped sufficiently to clear the mouth of the cylinder bore.
5 | The boot is located into the piston and is best removed with the piston. Lift the piston out complete with boot and secondary cup.
6 | Remove the primary cup washer, primary cup spreader, spring and bleed (or trap) valve assembly. To dislodge these items it may be necessary either to bump the casting on a block of clean soft wood to dislodge them or alternatively to apply gentle air pressure at the hose union bore and blow the parts free.

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