Trying to fault-find this with a strange earthing problem.
Park light and rear light don't work - can't find the feed anywhere.
Indicators flash at 2x normal rate and stop if the headlamp unit is screwed back onto the shell.
This bike has an external switch on the headlamp shell for the lights, together with a main beam indicator lamp set into the top of the shell. I'm assuming that this isn't standard (?)
My CB175 was a K4 and it was 1976 so I don't really remember the setup of the light switches...