60s Bonneville Headlight Color Temperature

Can you explain?

 

I assume that you're talking about the colour temperature of the light output from headlight dip and main beams?

If so, what you need to remember is that most of the early-through-mid-sixties (and possibly later) motorcycle headlights used standard, prefocus, tungsten incandescent bulbs, mainly 55/40 watts output. By today's standards they were barely capable of lighting the front mudguard, let alone much of the road ahead! I exaggerate for humourous effect - but not by a great amount.

Remember, too, that the dynamo was still in use into the early sixties and its output was fed to the headlight through relatively poor wiring and a number of connections each adding its own value of current resistance.

The introduction of halogen bulbs and alternators in the mid to late '60s saw a massive improvement in the quality and quantity of light provided from headlamps, though many were still relatively low wattage at 35/35 watts. All in all the colour temperature of the light output would have been very much more towards the yellow, rather than white, side of a spectrum.

If you REALLY want to make your headlight look more classic period you could try something like these :-

https://nl.aliexpress.com/item/32556789637.html

https://www.amazon.co.uk/GoldVision-Yellow-55W-12V-2pcs/dp/B005BP5I7E


They look like they should show a more yellow'ish light output than the bright white of 'normal' halogen bulbs.

I would be VERY careful about riding unlit streets or country roads at night, though.