Small Engines (Lawn Mowers, etc.): Float problems, snapper riding lawn mower, briggs and stratton

Question
I have a Snapper riding lawn mower with a Briggs and Stratton 11 hp I/C engine. It will start with the air filter off but not with it on. It also has gas in the throat of the carb. I checked the float and the gas turns off when I push it up and flows when I let it down. I have cleaned it as much as I could with the carb still on. Could it be a bad needle and seat or does the float level need adjusting? All help is appreciated.
Thanks

Answer
I can only assume without seeing the air filter that the air filter is extremely dirty and is "choking" off the engine.   

The air filter replacement is the first place I would start.

If there is dirt in the needle and seat it will allow fuel to leak by.  

Shake your float and make sure you cant hear any fluid moving around inside-throw it in a bucket of water to see if it floats or sinks.

HTH

Dave