Choke should be fully open (vertical).

What we are trying to do here is to set the curb idle too high, to see if the carburetor will function on the main metering circuit. If so, then the idle may be reduced to a more normal setting, using this screw.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
If you truly believe "one size fits all," try walking a mile in your spouse's shoes!
The Carburetor Shop