something interesting here. My thought is do you have an electric fuel pump, if not get a facet on there 40105. just put in inline with the mechanical. Another thought. I been through hell with my problem similar to yours. today it flew fantastic this morning and than I landed and taxi to hanger. guess what, rough running and shut down and fuel was coming out of the right side. not a bunch but when I turned on the facet pump, holy cow just poured out the vent, not drips but a bunch. smacked on the carb and still coming out a bunch. go back a few weeks and this happened and removed the bowl and found my new blue float stuck on the pin, on the bottom. I took and made sure the openings were ok and didn't find any more problem at least until this morning. did it again. did some checking and I find out the pins are having trouble in the bowl. to be exact the left carb, well in my model 4 that carb is now on the right. needs that for things to fit with a 912. you put the left carb on the right. well anyway I called lockwood and yes a redesigned left bowl almost black in color. I asked for the right carb bowl and was told that one is an original design. crazy, so I got the black bowl coming. oh and my problem a couple months ago was identical to your problem.