A carburetor works by drawing air over a main metering nozzle. To keep a constant amount of fuel to the main metering nozzle the carburetor uses a fuel bowl. The bowl is the round cup at the bottom of the carburetor. To maintain the constant level there is a float and needle inside the bowl. The needle can block fuel from entering the bowl of the carburetor. The needle is attached to the top of the float. When the level in the carburetor is too low the float drops and pulls down on the needle. The needle will pull out of its seat and allow fuel in. As the bowl fills up the float will rise. When the level of the bowl is enough the float presses the needle against its seat and block the fuel flow. This process repeats over and over.
It sounds like the needle is not blocking the fuel flow and fuel is coming out of the main metering nozzle. This could be due to many reasons; hole in the float, misaligned or stuck float, missing or bad needle, just to name a few. To check you will have to remove the bolt holding the bowl on and check to see what is going on inside.