A couple of points:
In Canada we had manual choke B21A until 1984 model year. In 1985 our
pollution laws changed, and carbs went away. James, if you want to see
manual choke car, just nip across the border north of you there, there's
plenty of those cars still running around in Vancouver and on the
island.
And older SUs (like the pair in my 1966 122s) accomplished the choke
function by lowering the fuel jet so that a narrower part of the fuel
needle was in play.
SU type carbs were just about universal on motorcycles, even the highest
performance models until a few years ago - fuel injection is just
starting to be more common.
