To check for spark, remove the plug wire and position it where the metal tip of the wire is 1/4 inch from plug tip. Crank the engine and if you are getting a spark it will arc across the gap.
Things to check...
1. Plug gap?
2. Is the fuel old?
3. Carb problems - choke working or stuck?
4. Flooding
Sometimes you can coax an engine to start by removing the air cleaner and putting a few drops of gas directly in the carb.