During the past month I had been struggling with fuel venting overboard and thought I had it fixed and over with but it suddenly returned on one carb. While investigating I noticed that the float valve arms on that carb were bent in towards the center of the carb. In all my previous messing with the float arms I must have inadvertently squeezed them inward to the point where they were no longer consistently riding on both float side pins. A simple act of straightening the arms out solved the issue with no more venting. Add that one to the list of things to check when investigating the accursed 912 carb fuel venting.