A SWITCH IN TIME
Apologies to Jethro Bell – and anyone else who sent in postal queries just before or during lockdown. The spiders who’ve taken over the CB office are terrible at forwarding letters, so I’m a bit late answering this query about how to wire a two-position ignition switch for his 1955 Triumph Tiger 110. He has upgraded to 12v with a solid state regulator and had the magneto converted to electronic.
First thing is to work out what functions you need, Jethro. If the switch is only two-position, you’ll need a separate light switch, and assuming you want both ignition and lights to be key-controlled (so kids can’t turn the lights on when parked) the switch needs to separate the battery and charging system from the feed to the ignition and light switch, meaning you can manage with just two wires.
Jethro’s switch has four: red, black, black/white and green, which sounds like it’s off a Japanese lightweight with direct ignition. Black/white is an ignition wire and green is earth, so I suspect these two connect in the ‘off’ position, cutting the ignition by shorting low-tension ignition current to earth. When ‘on’ the switch will break that connection, but join the red and black for other functions, so red and black are the two to use.
I’d join the battery live and regulator DC output (usually red or black depending on earth polarity – ie red on a negative earth bike) and connect these to one switch wire, then join the wires to the ignition and light switch and connect them to the other.
You could just have the battery on one side and everything else on the other – but if you do, the charging circuit is permanently connected to the ignition, making it possible for the bike still to run off the alternator with the ignition switched off.