Electronic spark ignition has been the standard for motorcycles since the late 1970s. Electronic ignitions have many advantages over the older mechanical contact points. Electronic ignitions are smoother running, and result in better fuel economy and lower emissions than the original mechanical points and condenser systems. Boyer Bransden is a popular manufacturer of replacement electronic ignitions systems for older English motorcycles. Installing a new Boyer system is relatively easy with a few simple tools and the right information.
Open the seat to gain access to the ignition coils. Remove the fuse from the negative (-) terminal of the battery. Remove the black/white and black/yellow wires from the condensers and ignition coils.
Remove the white/yellow wires from the negative terminals of the ignition coils. Remove the ignition coils and install 6 volt coils. Remove the red wire going to the ground terminal on the condenser unit and remove the condensers.
Connect the red wire to the positive (+) terminal of ignition coil number one. Install a jumper wire from the negative (-) terminal of one coil to the positive (+) terminal of coil number two. Install the Boyer transistor box in a convenient place near the ignition coils where it will not be subjected to excessive heat or vibration.
Connect the red wire from the transistor box to the positive (+) terminal of ignition coil number one. Connect the black wire from the transistor box to the negative (-) terminal of ignition coil number two. Connect the white wire from the transistor box to any one of the white/yellow wires removed from the ignition coils in Step 2.
Connect the black/yellow wire from the transistor box to the black/yellow wire removed from the ignition coil and condenser in Step 1. Connect the black/white wire from the transistor box to the black/white wire.
Remove the contact breaker cover and remove the contact breakers, backing plate and auto-advance unit. Disconnect the wires from the contact breaker plate. Remove the auto-advance unit from the shaft by putting a small piece of steel rod down the centre and tapping it around until it drops off the taper.
Install the Boyer magnetic rotor into the taper from which the auto-advance unit was removed. Hand tighten the cap-head screw and washer provided with the Boyer kit. Install the Boyer stator plate where the contact breaker plate was originally fitted. Set the stator plate about halfway along its adjustment slots. Align the stator until the magnet screw can bee seen through the timing hole in the stator plate.
Tighten the cap-head screw using a 3/16-inch Allen key. Connect the black/white wire to the black/white wire on the stator plate. Connect the black/yellow wire to the black/yellow wire on the stator plate. Ensure the connections are clean and tight.
Tighten down the stator plate with the original pillar screws from contact breaker unit. Install the breaker plate cover and replace the fuse in the negative (-) terminal of the battery. Start the engine and bring it up to normal operating temperature. Adjust the timing by following the manufacturer's procedures for your engine. The timing is advanced or retarded by moving the stator plate on its slotted holes.
The Boyer Bransden electronic ignition produces extremely high voltages. Use caution when working around the high tension leads on a running engine to avoid an electrical shock.