As most think, this does not indicate the throttle shaft needs to be re-bushed.
Gas is running down the throat of the carburetor and when it hits the throttle valves, it follows the path of least resistance and that is out the throttle shaft.
If this happens while the engine is running then you are flooding.
If this happens right after turning off the engine, then it is most likely due to percolation. This happens when the engine gets hot, and the gas heats up and expands. When the gas gets high enough in the float bowl, it runs out of the venturi and down the carburetor throat. Gas has a lower boiling point than it used to so the fuel system can’t handle it as it once did. There isn’t an easy solution to this other than making sure the fuel lines are away from the exhaust manifold. You may also want to try different brands of gas.