Small Engines (Lawn Mowers, etc.): B&S 13D777 Loading up with gas, needle valve, best bet

Question
I have an 18hp B&S OHV model 13D777, type 0233"E1", code 0212132A. It will continually allow fuel to flow. It filled the cylinder and cranck case. I thought it was the float so I replaced the float, needle valve, and seat, seat was a PITA. It ran for about 30 mins and then it back fired from my butt coming off the seat. After this it began leaking again so I put in another needle valve and it still flowed gas at all times. I gave up and bought a new carb. Ran fine for 45 mins and when I shut it off it backfired. As soon as this happened it started flowing gas again. Once off I pulled the PCV line from the carb and while it had some gas in it it did not get in the crankcase. It was still "gugling" so I pulled the spark plug and it stopped making noise but continues to flow gas unless the line is pinched. At my witts end. The float/needlevalve/seat control the flow and all have been replaced so it must be something else. Help please the grass is growing.

Answer
 Hello Phil:

 I hate to say it but your best bet is going to be buying a cut off valve for the fuel line and turn it off each time you shut off the engine. I have one of these motors on my garden tractor.  Its a Carb Problem but theres no other fix for it. I have had over 5 NEW CARBS and each one does the same within an hour of using them.  Hope this Helps.

 Good Luck

 Respeectfully

 John