If you hit something definitely check the flywheel key. Also the usual flooded / oil crudded up plug issues.

The other major problem can be if there is any dirt in the fuel bowl, it plugs up the carb. The most likely spot for this is a bolt at the bottom of the fuel bowl, 1/2" head I think that has the head at the bottom and threads going up. Pull this bolt, ( fuel will run out since the float now thinks the carb needs fuel). When you take the bolt out - have someone hold up the fuel bowl so it doesn't fall down.

In this bolt is a sideways and then vertical hole. I have heard this called the "bubbler". Any dirt in this passage way will stop the engine from running. Blow it out or use a small wire.

Good luck!