Re-wiring, Part 3 (Switch loom) – 24 Nov 2015.

My next job was to produce the other small loom which is soldered to the handlebar lights and horn switch. I’m going to use the original chrome “snuffbox” switch which is in good condition without any melted contacts. The wiring is also in very good condition apart from one point where it looks like it has got trapped and cut the sleeving and the insulation of one of the wires inside. There was also a very perished rubber “T” piece in the loom. I hunted for ages trying to find a replacement and eventually came up with a nearly identical item at Disco Volante Moto here in Wales.

I removed the old sleeving and wiring terminals after checking that the wires were plenty long enough. The damaged insulation to the horn wire was repaired with heat-shrink sleeve.

I had planned out and drawn the alterations to the switch loom.

Switch loom

As I am adding relays to the headlamp circuits, the two wires (green and green/black) which originally went from the switch to the headlamp needed to be extended and diverted back toward the main loom. I don’t really like to solder joints in a loom as they restrict its flexibility. However, here I felt it was the best option because, if I were to unsolder then resolder the contacts at the switch, there’s a good chance of me damaging it.

Two new wires then need to be brought up from the main loom to the headlamp. As these have the same colour code as the originals, I added purple heat-shrink tags to them.

The earth return for the horn circuit was originally via the switch casing to its fixing screws, the switch-fixing screws to the clutch lever bracket, the clutch lever bracket to the handlebar, the handlebar to the fork stanchion, the fork stanchion to the headlamp bracket, the headlamp bracket to the headlamp shell, then the headlamp shell to the headlamp earth wire which is grounded to the rectifier bracket. A jumper wire is then needed as that bracket is mounted to the painted frame with rubber washers! I don’t think this is a reliable way of doing things.

However, improving this earth is difficult as there’s no way to put a soldered connection on the chrome switch casing. The best I could do was to add a wire with a tag to a fixing screw inside the switch.


A 3.5mm solder tag was nice and snug, requiring the screw to be wound through it but, is at best, optimistic as a long-term solution. I did test continuity between the switch case and the end of the cable with my meter. At the moment it’s very good.

I used “bullet” connectors on the headlamp wires. Plugs on the switch wires to the relays and sockets on the load wires from the relays to headlamp shell.



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