The pilot reported that in cruise flight he positioned the fuel selector to the right auxiliary fuel tank and set a timer for 20 minutes. He practiced private pilot maneuvers and then proceeded to a nearby airport for touch-and-go landings. He did not switch the fuel selector back to the main fuel tank because he did not notice the timer. The pilot completed one touch-and-go landing and during the initial climb, the engine experienced a total loss of power. He pitched the nose of the airplane down for a forced landing and the engine regained power momentarily. The engine again experienced a loss of power, the airplane stalled, and impacted the ground adjacent to the runway resulting in substantial damage to the fuselage. The pilot reported no preimpact mechanical malfunctions or failures that would have precluded normal operation. He stated that he should have refueled the airplane before the flight, so he did not have to worry about fuel management.