Until the carb and intake heats up a little, only a fraction of the gas coming through the carb actually vaporizes before it gets to the cylinders, so keeping it a little rich for a minute or two is a good idea. Until the tree huggers started having a freakout over a few extra hydrocarbons, it was a lot simpler to make an engine run smooth during warmup. Just before everybody went to fuel injection, there was actually a federal law we had to comply with about how long an automatic choke could stay applied! I think it was 1 minute above 70 degrees F., and 2 minutes below that temp. That took a BUNCH of fancy adjusting, vacuum pull-offs, and electrically-heated choke coils!
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!