How Does an older Carb without a Choke Pull Off Do It?

I understand a choke pull off keeps the engine from running too rich at initial cold start-up. So I was wondering how a '65 carb without a choke pull off can do the same thing, or can it? Thank you.

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Looking good. PS, they sell the plastic plug wire insulators. https://www.megapartsusa.com/proddetail.php?prod=101-PWBAX5