Old Britts – Installing Boyer Bransden MKIII Ignition Units for Nortons
Download the complete PDF version using the green download button at the top right of this page for an Old Britts reprint of the Boyer Bransden MKIII electronic ignition installation sheet for Norton motorcycles. This technical reference explains the components supplied in the ignition kit, the initial timing position, magnetic rotor and stator plate alignment, transistor box mounting, coil wiring changes and the final stroboscopic timing procedure used to complete the installation correctly.
The guide begins with the parts included in the Boyer Bransden system, such as the transistor box, stator plate, magnetic rotor, fixing bolt, plastic strap and bullet terminals. It then covers removal of the original contact breaker assembly and auto-advance unit, setting the engine to 31 degrees before top dead center, fitting the magnetic rotor in line with the Norton timing case marking and positioning the stator plate so the magnet aligns with the timing hole.
Later sections explain the wiring changes required at the timing cover, ignition coils, ballast resistor and condenser pack, together with the installation of the black ignition box on the frame tube. The article also includes wiring diagrams, rotor and stator alignment drawings, black box placement illustrations and final timing instructions using a stroboscope at up to 5000 RPM, along with notes on coil choices and primary resistance requirements.
Contents Include
- Boyer Bransden MKIII electronic ignition installation for Norton models
- Ignition kit component identification
- Contact breaker and auto-advance unit removal
- 31-degree BTDC initial timing setup
- Magnetic rotor position and stator plate alignment
- Atlas reverse-rotation timing note
- Timing cover wire and bullet connector guidance
- Ballast resistor and condenser pack removal notes
- Transistor box frame mounting and wiring connections
- Ignition coil wiring sequence
- Stroboscopic final timing procedure
- Coil compatibility and primary resistance guidance
