A C150's engine would not start using normal engine start procedures. On the pilot's second troubleshooting attempt; he failed to turn the Master and Magneto's off and exited the aircraft. After he moved the propeller slightly; the engine started and taxied across the airport unattended.

Narrative

I had the engine cowling removed to run engine to check for an oil leak. I pulled the handle to engage the starter. The engine did not spin over; starter did not engage. I exited the aircraft turning the Master and Mags off. I checked the wiring connection to the starter and moved the prop; everything seemed normal. I reentered the aircraft turned Master and Mags on; pulled starter cable; the starter did not engage again. I exited the aircraft again. As I walked by the prop I reached out and moved prop. The magneto fired and the engine started. I was not trying to hand prop the airplane; in fact I moved the prop just enough for the impulse coupling to fire. The aircraft sped off across taxiway through grass and across runway and flipped over on its back. I was unable to stop the airplane. I was frustrated that the aircraft would not start. I got in a hurry the second time getting out of the aircraft neglected to do what was normal; turning Mags; Master; and Mixture off. When I moved the prop and the engine started it was clear that the Mags were either left ON or the mags were not grounded. After the airplane came to a stop the key switch was found in the ON position and the mixture was rich. After airplane came to a stop the mags; master; and mixture were turned off. Frustration led to inattention to the task at hand; operating in and around the aircraft in a safe manner. I did not follow normal checklist procedures prior to exiting the aircraft even though I was not going to fly the airplane.