I just purchased a replica Lucas horn/dip switch. This is the one with the large round chrome horn push and the black plastic dipper. I imagine the item is a pretty common purchase for later bikes (mines going on a 1967 Velo MSS). The replica switch has non-normal wiring colours as follows:
Red-black Blue-white Blue Brown
I've figured out that Red-black is the horn-push but I'm having trouble with the others which are to do with lighting. One is connected to the lighting switch and supplies power to the dip switch and the other two go to the high and low beams on the headlamp bulb holder. Can you tell me which is which?
Try brown as a power wire then test Blue/White and Blue as the high and low. Two pieces of wire with alligator clips at the ends with a battery should get it proved out. A tail light bulb with wires and alligator clips will tell if the power is coming back out of the switch.
norbsa 1960 TR6 1963 Super Rocket 1965 650 Star 1966 441 1968 Thunderbolt 1969 Twinkle 250 1972 Fastback 1974 Roadster 1970 S.S Way too many BSA's not named http://decentcycles.com