Well I’ve resolved the problem with the switch unit… for now.
I bought a cheap (probably Chinese made) switch unit for High/Low beam, turn indicators and horn. It doesn’t have lights On/Off so I’ve decided to use a toggle switch for that. I chose a DPDT On-Off-On switch so that one half of the switch covers the pilot lights, front and back, while the other half covers the headlamp power to the dip switch. This way I can have the pilot lamps available both when the ignition is turned on and when the key is turned to the “park” position and removed. The headlights only available with the ignition in the “run” position.
There is an unused fuse in the fusebox on the far right as you look at it. The one to its left is the only one that receives power in the “park” position as well as in “run” and is normally where all the lighting circuits get their power. In my system this fuse will only supply the pilot light circuit. A jumper wire was added from the top, supply side, of the third fuse from the right to the top, supply side, of the spare fuse on the far right. This new fuse will be my supply to the headlight circuit.
It’s not really as complicated as it sounds and, yes, I know, I could have swapped things around so that the pilot light circuit was on the end.
I had already fitted a plate to add extra indicator lights to the original instrument cluster. I made a new version to provide room for the toggle switch. This has a waterproof cover. It’s not a thing of beauty but is fine for now.
When tested all worked as intended. If you ride with the headlamps on, they switch off with the ignition as before. If the key is turned left to the “park” position just the pilot lights come back on.
I’ve ridden the bike and I can manage this switch arrangement without any difficulty. I’ve also ridden at night for the first time and the dip beam provided by the Wipac Quadoptic headlamp and Nightbreaker bulb combination is fantastic. Main beam is ok but seems to have a hole in the middle of the spread of light.
I’ll keep a look out for a more “period” handlebar switch to possibly fit next winter. Something from a 70s Yamaha would probably be ok.
Next job is to go through the ignition HT circuit. Then to tune and synchronise the carbs. I’ll also draw a new wiring diagram showing the new switches.