POOP! You've sure had your share of problems lately. The fact that it dies but will start again after a couple o' minutes does make one think it might be fuel related. You can open the drain plug on each carb to see if fuel pours out readily. Maybe rig up a way to catch the fuel and let it run for a couple of minutes. If there's any crap in the tank, it would draw said crap to the petcock filter. Which is another thing to check... the petcock filter.
I'd still do Ted's idea and run the bike with the cap open. Ya never know.
