There’s another adjustment screw on my carburetor, a little bit to the left of the idle adjust screw, a little bit beneath it, pointed more upward, not-seeable when the air cleaner is mounted. It’s the 22 R engine.
The Chilton’s diagrams of the 8, 18, and 20 engines have ‘fast idle adjusting’, ‘mixture adjusting’, ‘throttle position adjusting’ screws, not the 22R’s diagram.