Fitting a Boyer to a Dommie twin
Fitting electronic ignition to old Brit bikes is usually straightforward, and Boyer’s is probably the most popular system. They cover a good range of bikes, their website has detailed, model-specific info, and you can speak to someone intelligent if you hit a snag.
The basic idea with a Boyer is to unscrew the points and mechanical advance/retard, and screw in a rotating magnet, followed by a plate with a coil or two. As the magnet spins past the coil, it generates an electrical pulse which goes to the ignition box. The box amplifies the pulse into a spark, and obligingly provides an advance curve to replace the function of the original bobweights.
Once you’ve ensured that the spark happens at the right moment (you’ll need a strobe light), you tighten everything up and enjoy excellent starting and permanently accurate ignition timing. Which is fine – until you discover there isn’t a kit for your bike, such as this single-carb Norton Dominator in a Featherbed frame. I was making a new loom for it and the owner, Jono, wanted to take the opportunity to convert to electronic ignition.
A call to Boyer revealed they don’t do a kit for this model (nor does anyone else!), and suggested
I call Alan Osborn at long-established AO Services in Norfolk (01953 884681). Alan uses Boyer components to make a rotor and coil that fit inside the original 18D2 distributor housing, plus a single-cylinder amplifier box with two 6V coils. The kit costs £165 including P&P, plus an £18 optional aluminium cap to tidy up the distributor.
Electrically, it’s as simple as any other Boyer. Two wires take the timing pulse from the source coil to the box. Three wires go from the box to the rest of the bike. One of them is live when you turn the ignition on (and also connects to the coil live terminal), one is earth and the third sends the signal to the coil. It works perfectly, but when you’re dealing with a 55-year-old cafe racer there are a few other snags to overcome. Turn over to find out how to deal with it.
‘BOYER REVEALED THAT THEY DON’T DO A KIT FOR THIS MODEL’
Electronic ignition kits aren’t available for some classics, like this Dommieengined special, but we know a way around it...
Make a neat job like this and save yourself a lot of kicking – it’s not difficult