So, the engine rotates when the ignition switch is turned but will not start up and run on it's own.
Check the condition of the spark plugs.
Check the ignition wires and their connections.
Check the condition of the battery and fluid level.
Check battery connections, make sure cables are tight at the battery and clean.
Check the condition of the air filter.
If it almost starts then we can assume that it is getting fuel.
Weak or old spark plugs have a reduce "spark" and wear out over time and thus yours may need to be cleaned or changed for fresh ones.
