Old Britts – MK3 Rear Master Cylinder Rebuild Information
Download the complete PDF version using the green download button at the top right of this page for detailed Old Britts rebuild information covering the Norton Commando MK3 rear brake master cylinder. Written by Fred Eaton, this workshop article explains the rebuild kit options, dismantling process, internal cylinder components, cleaning requirements, correct reassembly order and the critical cylinder depth adjustment that must be preserved to prevent rear brake lock-up.
The guide covers removal of the reservoir, set screw, cylinder body, rubber cover, circlip, piston and internal rebuild parts, while also noting that the original piston should be handled carefully because replacement pistons were not available at the time the article was written. It explains the importance of cleaning the cylinder bore thoroughly, keeping the piston holes open and ensuring all parts are ready before the master cylinder is reassembled.
Further sections show how the body, push rod, jam nuts, spring, valve, rubber cup, washers and piston are assembled in the correct order. The article gives special attention to aligning the cylinder threads with the original set-screw mark, warning that threading the cylinder in too far can prevent the brake pads from returning to neutral and may lock the rear wheel. Reservoir positioning, spacer placement, O-ring fitment and final securing of the lock nut are also covered.
Contents Include
- MK3 rear master cylinder rebuild overview
- Old Britts rebuild kit 19-4700 and 19-4700/R information
- Reservoir, set screw and cylinder dismantling guidance
- Piston removal precautions and cleaning advice
- Cylinder bore and piston hole inspection
- Push rod, jam nut and body reassembly sequence
- Internal cup, spring, valve and washer placement
- Circlip and rubber end cover installation
- Critical cylinder depth alignment warning
- Reservoir spacer, O-ring and lock nut fitting
