Take the carb completely apart, clean it. Make sure to get every hole and passage cleaned out including vent lines and adjust make sure the float is adjusted properly. I assume when you checked fuel flow, you checked it by turning the fuel petcock on and watched fuel flow from the tank? If you are getting fuel through the petcock, and the bike runs when you prime the carb, then I would think that you are not getting fuel into the carb. In that case I would suspect that the float is your primary problem, but I would still give the carb a thorough cleaning if you haven't already.
Yours truly, sincerelly, love always, Josh aka The DirtDemon.