I think you have a stuck float or bad float valve.
It can only be one of two things, the obvious that Mike and Dave replied to or the not so obvious I wrote. Did you try anything suggested? A stuck float on an '88 will sometimes dump fuel overboard on that carb from the thicker hose on the left rear corner that goes to the metal pipe which sits behind air box. Disconnect that hose from carb and see if gas pours from there too.1988 Goldwing 1500. Replaced most every vacuum hose. Put it back together and it would not start. Took air filter off. Looked down throats of carbs. The carb on right is fine but carb on left is flooding cylinder with lots of gas.