First, to determine wither it's spart or fuel related. If you remove the air cleaner when it's not starting, shoot a small amount of carb cleaner or starting fuel into the carb and see if it runs a second ot two. If so, that would indicate a fuel issue. Plugged gas tank or anything between it and the carb. Gas cap vent and\or carb. If there is a solenoid on the bottom of the carb, it could be failing. For troubleshooting, remove it and cut off the small internal shaft. Replace later.
Spark issues could be coil, plug, plug wire. Remove the kill wire from the coil and see if it runs. Reattach to stop engine. If it runs disconnected, then there are many electrical devices that could cause it.