a motor needs spark, fuel, and air to run. to run correctly those parts need to be adjusted correctly
pull the plugs and hold it against the block or head adn have someone kick it over and look for a spark,
fuel: clean your carbs out, check your jetting. might have a big pilot or plugged up
air: clean your filters.
if still dont work then find out whats wrong and go from there. spark= electrical: stator, coil, cdi, etc