check reeds ?
a broken or badly cracked reed petal won't run/start
also check the flywheel woodruff key that alings the timing, if it's sheared and allowed the flywheel to rotate out of time, it'll have spark, but at the wrong time.
flooded crankcase can also cause no start/run.
remove pipe from cylinder, turn off fuel & drain carb, run switch to off, throttle wide open and kick till your leg hurts to purge raw fuel out