Sounds like you tipped your mower it's side with the carb and muffler down. Big no,no. Easiest way to solve, is to make a mosquito beater out of it. Keep it running with carb cleaner or starting fluid, until it will run on it's own. Then let it running until the smoke clears up. Have a cold case of drinks to ease the tensions of the neighbors, as it will get smokey. Always remember when tipping the unit, CARB UP.