Hi!
Can anyone advise if the 1960/1961 BSA M21 is positive or negative earth?
Would anyone have a wiring diagram for AA M21 with Sidecar and alternator fitted to the crank drive side?
Many Thanks,
Glenn
Your bike should typically be positive earth (they were -ve earth up to early 50s, maybe 1951 - someone who knows might correct me).
There was a change back to -ve earth in the late 60s (same for cars) which is still common practice now.
Hope this diagram helps:
(https://www.bsaownersclub.co.uk/bsaoc_forum/index.php?action=dlattach;attach=15109;image)
I would imagine an accessory loom with a pilot light/rear lamp feed and maybe brake light out to the double sided lamp that sits on top of the side car mudguard?