At 70*F that spring should unwind PDQ, in fact it should be almost limp.
If the engine idles ok after warm-up, that sorta indicates that the low-speed system is working.
That leaves just three possibilities maybe 4.
#1) would be the accelerator pumpshot
#2) would be too much idle timing, which puts the throttle blade too far down the transfer slot. It dries up, and then takes a MS to get started again.
#3) would be really old gas; fresh gas is clear to slightly yellow
#4) would be, lessee, oh yeah, I remember; a defective carb-heat system. That is the exhaust passage under the carb, the heat-riser valve, or the mixing valve in the air-cleaner, if your carb was calibrated for it.
Happy hunting.
BTW yes, that choke mech is designed to come off somewhere in the first three minutes, at freezing temps.
Also; in Ks you shouldn't be having this problem, but; at certain times of
the year, with high humidity, Carb-icing can cause that. Thois is usually a result of a throttle-valve that is too far closed, and lack off carburetor heats. When the conditions are right, ice will form on the outer perimeter of the throttle plate. This will restrict the airflow enough at idle that the engine will stall. This will not be related to throttle changes, it will just stall, apparently for no reason.
I just thought it was worth mentioning.
