Hoover300
Kieran,
I think I can get this solved regarding the wire setup for your D50:
* All white (negative) wires go to the side terminal screw. In this case, that would include those for the headlight socket and field coil
* All positive (live; hot) wires go to the bottom terminal screw; in this case, including those for the black brush lead wire (to bottom carbon brush) and headlight socket
* The long white and green wires emerging from the field coil go straight to the speed switch; the shorter green wire goes to the top carbon brush (as seen in the 4th picture you show us).
* The red and yellow wires go straight to the speed switch.
The foot switch I see on your D50 (part no. 110563) was the original one from the factory, and was also used on the initial 1967-68 season production run of the D80 (those units whose serial numbers begin with the letter "A"). The D80 got a redesigned field coil in June 1968, and thus so did its power switch.
~Ben[this post was last edited: 8/31/2020-17:27]