I knew that would get you going.
It is truly a Rube Goldberg setup. Eddie said the screws at the rear of the carb on each side are the primary and secondary idle adjustment. He also said the secondaries start opening at 1/3 throttle. I agree the first time you set it up would have been intimidating. You would appreciate the linkage quality. I wonder if the shafts are splined under the linkage? It seems it would need more than a pinch to stay in place.