Small Engines (Lawn Mowers, etc.): Gas leaking

Question
I have an Ariens 20hp riding mower...(motor model 331777--2372G5 briggs.  Yesterday, the motor would not idle and would only run on high rpm.  This morning when I went to check the mower, gas was dripping out between where the head attaches to block (underneath the bottom---there was no gas leaking from valve cover).  I took the valve cover off and there was aprox 4-5 oz of gas that poured out.  The valves seem to all be in adjustment as I rotated motor by hand and valves open and close properly.  Help?

Answer
Leaking inlet needle seat.  Has the carburetor ever been rebuilt?
 
Do you have an air compressor?  Have you ever rebuilt a carburetor?

Check You Tube for mower carburetor cleaning or rebuilding...there are lots of videos.

Let me know if you have an air compressor and any experience rebuilding carbs.
Eric