Welcome to the forum.
If a carb has been flooding the engine, the gas has to be getting past the petcock and the fuel needle inside the carb(s). You've rebuilt the petcock so the carbs need to be pulled and those needles and seats need to be replaced inside the carbs. Do not detach the carbs from each other would be my advice and do a mechanical throttle sync while they are off. And of course remove all the jets and emulsion tubes and make sure they are clean while you have the carbs out.
1985 Kawasaki ZN700 Shaft, 4cyl
1989 Yamaha Venture Royale
2007 Yamaha Royal Star Venture