Right out of the bat I agree with Van. Yank that kill switch outta there.
And with my own personal experience assuming you have a Happy Time engine,that's exactly what happened to me when my magneto failed.
Check for spark first though.
Also, try unscrewing the fuel tank cap. Mine tends to seal up too much when theres a full tank and it creates a vacuum on the tank, starving the engine for fuel. Once I open the tank and close it again, the engine comes back to life.