This is simple and self-evident to most anybody with a soldering iron but here we go….

First a primer on headlamps. Rated at 55 watts, an H4 lowbeam headlamp consumes around 55 watts, I guess, which is something like 4-5 amps. With a 240 watt alternator and with barely any charge below 2500 rpm, goofing around in the city, prior to cranking on a cold morning, or when your electric system is failing, it would be good to be able to switch off the lamp. Moreover, the parking lamp is on all the time and can make-do for a substantial part of the safety and regulatory issues, especially in the daytime. Finally, if you need some lamp action, you can always flick on the highbeam the two habitual ways which are unaffected by this mod.

So, the best Airhead approach is to cut the wire to the low beam (the yellow lead) and solder-in wires to a switch mounted anywhere you like. I had a spare hole in my headshell which needed plugging anyway so a bat-handled switch suitable for a 7/16 inch hole was just right. There are neat handlebar accessory switches too.

Any switch with a rating of 10 amps or more (or a dual-switch with two sets of contacts rated 6 amps each, wired in parallel) is good. Wires can be any reasonable weight, maybe 20 or a lower number – not a big thing for such short runs. But if you can, avoid ordinary lampcord in favor of something with a more automotive heat resistance. Try to remember to slip the heat-shrink insulation on to the loose wires before soldering the wires together, eh?