Gasoline leaks out of the carburetor because the needle on the float inside the carburetor is not stopping the flow of gasoline into the float bowl. The bowl overfills with gasoline and the fuel goes up into the carburetor and probably into the oil as well. Check the oil before running the engine and if there is fuel in the oil, change the oil.
The problem is usually caused by debris from the fuel line between the fuel tank and the carburetor getting into the seat in the carburetor where the needle valve on the float assembly stops the flow of fuel into the carburetor. A defective float in the carburetor can also cause this.
You can probably repair the problem by removing the carburetor from the engine. Remove the fuel bowl on the bottom of the carburetor. Remove the float and needle being careful to not lose the needle or spring if it has one. Clean the debris from the seat that the needle goes into.
Replace the fuel line from the fuel tank to the carburetor. The debris usually comes from the deteriorating fuel line.