Check and clean the air cleaner and spark plug. Be sure the fuel in the engine is no more than 4 weeks old.
If the spark plug has oil or carbon on it, clean it off and check the engine oil level. If the engine is overfilled with oil, it will blow oil on the spark plug.
If the engine won't start I am sending you a method for checking it out.
You need to decide if the problem is no fuel or no spark.
Remove the spark plug and hold your finger or thumb on the hole the spark plug screws into. Get someone to pull the starter rope or engage the starter and the compression should push your finger off the spark plug hole. This will tell you the valves are operating inside the engine and you have compression.
Pour a thimble full of fuel into the hole the spark plug came out of. Quickly install the spark plug and pull the starter rope or engage the starter. The engine should try to start. This would tell you there is a spark and the engine will run if you get fuel. If the engine doesn't try to start, pour another thimble full of fuel into the cylinder. Look at the anode of the spark plug and see if it is wet. Try to start the engine again. If it still doesn't try to start, remove the spark plug and connect the ignition wire to the spark plug. Hold the bottom of the spark plug to a clean area on the engine block. Use insulated pliers or gloves to hold the spark plug to prevent shock. Get someone to pull the starter rope or engage the starter and see if you get a blue spark from the anode of the spark plug to the base of the plug. If there is no spark the ignition module on the engine is bad.
If you have spark the problem is in the fuel supply. Did you run the engine after draining the fuel to burn the fuel out of the carburetor? If not the carburetor will be clogged with the remnants of the old fuel and need to be replaced. If you ran the fuel out of the carburetor, the diaphragm or float is probably just dry and not flexing. You should take the carburetor apart and clean and soak the diaphragm with fuel or clean the float and needle and seat..
The fuel line might be cracked and letting air into it stopping the fuel from feeding the carburetor.
If you need more advice after trying these things, send another email and include the details of your tests and we will try to help.