Here is a tip for you. Check the power valves on both carburetors. If the power valve or round gasket is broken, it may let the gas leak into main body "vacuum chamber". If this is the case, the gas will leak into the engine without you seeing it and it floods the engine. If you open up the carbs, remove the bowl and metering block carefully to see if the chamber is wet. If this is the case, you have leaking power valve(s).