I remember setting one up, and the idle circuit was on the primary's on both carburetors, and each carburetor served only 4 cylinders. You had to work at getting them synchronized properly, and they ran smooth once you got that done. It was more of a "balancing" act than anything else. The linkages had to move smoothly and in exact synchronization. It could be done, but most people didn't have the patience to do all the adjustments exactly, and you had to have 2 carburetors that responded exactly alike when the secondary's opened up. Everything from float level to jetting had to be exactly alike.