I think your float may need adjustment, or replacement. Sounds like it may be getting stuck open, thereby letting too much gas in to the carb. When you take your carb off again, make sure to take the bowl off and clean in there, and check to make sure the float can move up and down easily. To check it for leaks, you'd have to see if you can hear any gas sloshing around inside when you move it around. Don't use acid to clean the float, as it may destroy it, just some carb cleaner will do. The black smoke is an indication of too much gas...
Rattosh51
YT6800