You are correct sir,.... my mistake. The wires from the ignition switch are indeed double white and double BROWN and BLUE not GREEN as i stated earlier. My apologies for the misinformation. Your humble friend,....R.T.Hi Rod,
So not an original harness, which is what I based my previous advice on. Given the other differences you've mentioned, an educated guess says it's Wassell "Genuine Lucas" ...
Are you sure the tracer's definitely Green and not a shade of Blue? Brown/Blue was the 'original Lucas' colour code for the wire attached to the battery "not-ground" terminal since some time in the 1950's; any bike not fitted with an Ammeter, Brown/Blue continued to the ignition switch.
'Original Lucas' did not use the same wire colour/s for entirely-different connections. Specifically Brown/Green was always the 'original Lucas' colour code for wires to pilot bulb and rear bulb tail filament - as you've noted, there are two Brown/Green wires attached to Lighting switch terminal #7; if you wish to be sure, use an Ohmmeter or the Ohms function of a multi-meter to test continuity between Lighting switch terminal #7 and those two bulbs.
Otoh, if you test continuity from the ignition switch, you'll likely find one Brown/whatever wire goes to the rectifier and battery -ve, the other Brown/whatever wire goes to the Zener.
Original '78 T140E-specific harness didn't have either Brown/White or Brown/Blue from ignition switch to Lighting switch; these are Lucas colour codes specifically for unswitched connection from/to the battery ('78 T140V has Brown/White).
At the Lighting switch, you should connect the Brown/Blue wire from the ignition switch to terminal #4 specifically (not #3).
This specifically depends on the ignition switch connection of the Lighting switch Brown/Blue wire in your bike's harness. As in my previous post, the ignition switch has either three or four male spade terminals:-
. if three, you can see two terminals are connected together and one isn't;
. if four, you can see they're connected together in two pairs;
. risking stating the obvious, terminals not connected together on the outside of the switch, are connected together inside the switch just when the switch is 'on'.
White is the Lucas colour code for wires switched by the ignition switch. Otoh, as I've written above, one of the "Double Brown/whatever" wires is unswitched from battery -ve.
So, with "Double white" on one terminal and "Double Brown/whatever" on another terminal not visibly-connected to the White wires' terminal, the White wires are energised only when the switch is 'on' (or the switch is faulty).
So, if you connect the Lighting switch (Brown/Blue?) wire to the ignition switch terminal visibly-connected to the White wires' terminal, the lights will be switched on and off with the ignition.
The reason Meriden used a 31788 (or 35710) Lighting Switch on the '78 T140E is specifically within those switches terminals/positions #1, #3, #5 and #7 are connected together internally.
So, on an original '78 T140E harness, if a White wire switched by the ignition switch was then connected to Lighting switch terminal #1, and terminal #7 has the Brown/Green wires specifically to pilot bulb and tail filament, those two bulbs would be illuminated all the time the ignition is switched on, to comply with the 1978 FMVSS.
Blue supplies the headlamp dipswitch on the handlebars. One Lighting switch position connects terminal #7 to terminal #8. So the headlamp will be on in one Lighting switch position and off in the other two.
Not if you carefully read and follow all my advice.