starting facing downhill

You only need two things for a motor to run- fuel and spark.
I get ya, and not to nit-pick but just incase somebody else reads this you need air/fuel mixture to be somewhat ballpark correct, timing (be somewhat close on both ignition and valve), and compression to go along with your spark/gas. I know it's not the OP's issue, and I don't know what it would be other than what's already being suggested.