What color is the spark? It must be white. If yellow the plug, coil gap, or coil itself/high tension cable are at fault.
What is the coil gap?
How is the key on the flywheel?
What is the compression of the engine?
Did you pry out and clean the black plastic idle jet? It is open to the world and can clog easily. If clean how is the tiny "O"-ring on the jet?
If cut,torn,rotten the engine will not run properly.