DIAGNOSIS With fresh fuel ruled out, you're down to spark, compression, or a severe fuel delivery blockage. On these, a fouled spark plug or a dead ignition module are prime suspects.
FIX Pull the spark plug. Check if it's wet (flooded) or dry. If it's dry, you're not getting fuel. If it's wet, clean and gap it (0.020 inches) or just replace it—they're cheap. While the plug is out, ground it against the cylinder and pull the starter cord to check for a bright blue spark. No spark means a bad ignition module.
IF THAT DIDN'T WORK If you have spark and fuel, check that the on/off switch isn't stuck in the stop position internally. Also, make sure the fuel tank vent isn't blocked, creating a vacuum that prevents fuel flow.
HEADS UP Never pull the starter more than 5-6 times with a flooded plug—you'll just hydrolock the engine. Always pull the plug first to check and clear it.