The pilot reported that the airplane was being flown to another field, about 40 miles away, for repairs to the left wing fuel tank. He said he was burning the fuel from that tank for the repairs to be done. En route the tank ran dry and he switched to the right tank. He also stated that impending weather forced him to abort the flight, so he was returning to the departure airport. While on a 2 mile final approach to the runway, the engine quit. A forced landing was made in a field with tall wheat and the airplane nosed over during the landing roll. Twenty minutes elapsed between the pilot's stated takeoff and landing times. Inspection of the airplane revealed that the fuel selector was on the right tank. All of the fuel was then drained from the airplane. The following fuel quantities were drained: 1.5 gallons from the right tank, one quart from the left tank, and two ounces from the gascolator. Fuel was replaced in the airplane and the engine operated normally. Unusable fuel specified for the airplane is 10 gallons.