On a Carter W-1, the brass screw with the blunt point is the mixture screw......out approximately 1 full turn front lightly seated. The other screw is the throttle positioner screw a.k.a. curb idle screw, and rotates the opening of the throttle plate. After the engine is up to normal operating temperature, adjust this screw to adjust engine idle RPM. Clockwise will increase RPM, counterclockwise will decrease RPM.

Jon.

Good carburetion is fuelish hot air
The most expensive carburetor is the wrong one you attempt to modify.
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The Carburetor Shop