Takes 3 things to make it run.....spark, gas, and air. I'd check the spark at the plug. Pull one out leave it connected to the wire and turn over the motor.....should be a nice blue spark. White or yellow is weak and may not be enough. Also smell the plug and check if it's wet with gas. Maybe you flooded it?
Check the firing order as well. If you mixed a couple up it won't run worth a crap. Everyone has made that simple mistake over the years.
