DO NOT AND I REPEAT DO NOT CRANK THE ENGINE AND LET THE GAS SPRAY OUT. I used to do it that way a few years ago until I had one were the carb leaks and I pulled the spark plug out, disconnected from the wire, and in my hand with the plug wire sitting about 4 inches from the engine. Got on the seat, while holding the disconnected spark plug in my hand. The first crank sprayed gas, the second crank sprayed more gas, this is going all over the mower, and on my wooden board trailer. Third crank lit it. Spraying gas causes static electricity which can arc and ignite. If I wasn't carrying a fire extinquisher I would have lost the mower and my trailer.
Always use an air hose to blow out the gas from the cylinder, and I repeat to no crank the engine to expel the gas from the cylinder.