Husqvarna zero turn mower won't start

My wife mowed a few times this season. The last time she mowed, she said it sounded as if the engine was running faster than normal when the parked it in the garage. Now it won't start. Is there a governor on the motor? It is a Briggs and Stratton 24 hp extended life engine. I cleaned the air filter, checked the fuel pump and checked to see if the plugs were getting spark. Everything looks great. Could the float be stuck in the carburetor?  When I crank it, it doesn't hit at all. The parking brake is on and the seat switch is depressed. If it was one of the sensors, I don't think it would even crank. The model is Husvarna ez4824.