They idle on all 3 carbs. There is adjustment screws on the lower base. You have to pull the rear carb to adjust it unless you an aftermarket plate. If they are dumping fuel is the float level adjusted right?
The out side carbs operate on vacuum and will open under load. There are springs in the vacuum pods you can change to make them open slower or later. The linkage actually pulls the carbs back shut once you lift off the throttle.