Here’s the mixing valve on the ’37 Thor built Sea king I am currently working on. A very simple device with one moving part. The original mixture needle was missing but the new one I make for it will have a small knurled dial on it.
The next picture shows another members Thor motor. Apparently Thor Hansen used a bent piece of rod for the needle. 😯
I’m not sure why Elmer kept using them if he improved them enough to work and used carburetors on his own motors. Maybe they had a crate full of them and had to use them up.