So-called 'electrical engineers' for manufacturers were (and sometimes are) notorious for calling out inadequate wiring gauges
Lucas generally used their 14 strand wire, rated for 7.5A, which exceeds the current consumption of any individual electrical component.
Ime, before 71, Lucas used 28 strand (rated for 15A) for wires common to more than one circuit - primarily the Brown/Blue (then used to connect battery negative to one Ammeter terminal), Brown/White (then used to connect the other Ammeter terminal and at least the rectifier to the ignition switch) and White/Blue. So I have never understood why, 71 onwards, when the standard RM21 alternator was rated for 10.5A at 5,000 rpm, Lucas used 14 strand for all wires, including the Brown/Blue then between battery negative, rectifier, Zener and ignition switch;
the difference today is pennies when wire is bought retail, then it cannot have made any noticeable difference either to the amount Lucas charged BSA or to Lucas's costs? The only thing in the change's favour is it does continue to work, although ime the 14 strand Brown/Blue does not have any spare capacity.
the infamous 'bullet' connectors used in British bikes and cars--that predictably increase resistance as they deteriorate, especially in humid climes. This, of course, is done to facilitate quick and thus inexpensive assembly
The primary problem with electrical connectors is owners expect them to last much longer than either vehicle makers or harness makers designed for. Vehicle owners' manuals did not (and still do not) have anything about electrical connections maintenance, the average vehicle owner does not think about them until they do not work, then bitches about the poor quality.
Ime, the bullet terminals and snap connectors Lucas supplied are no worse, and no better, than the bullets and sockets the Japanese electrics makers use; the Japanese could be better, if they pulled up their harness makers but, for whatever reason, they do not.
You will not be aware of it until you own one but Lucas electrics on most Triumph and BSA triples are more reliable than those on contemporary twins, simply because most triples do not have the big clump of bullets and snap connectors under the tank, with one end of each snap connector to collect wind driven water that makes its way between tank and frame ...
Also typical with older 20th century vehicles was running a bunch of current through switches rather than using relays, a practice which back in the day was one cause of vehicle fires or just melted wires.
As I say, the rating of the wire Lucas used on motorcycle wiring harnesses exceeds any individual component's current consumption; however, that never took account of increasing resistance at corroding terminal connections because owners did not even look at them from one decade's end to the next ...
Similarly, I do not know of any o.e. Lucas switch that was not capable of switching the current drawn by the switched component. Ime, switch failure causes are normally owner neglect and/or failure of designers to consider environmental factors - adequate waterproofing, use understanding (e.g. that owners would attach fobs and other keys to an ignition key, the switch would be affected by the weight of other keys, fobs flapping in the slipstream. etc.). In some respects, design time limitations had to be set by the maker because the buyers would not pay more than the absolute least possible.
First thing I did on the present '71 Bonny was to install a VW Beetle '67-79 headlight relay
allows you to use one of the momentary buttons on the OEM controls to handle a few milliamps rather than the full current for the headlamp bulbs.
Like you, I have long used relays to supply/switch the headlamp, but that is because I fit headlamp bulbs that draw considerably more current than o.e. However, o.e. headlamp bulb filaments draw less than four Amps, a relay would have been overkill (and unjustifiable expense for the buyer).
