The complete loss of engine power due to failure of the No. 1 main bearing, and the secondary failure of a crankcase through-bolt and the fuel pump drive coupling. Contributing to the accident was the pilot's decision to attempt a return to the airport for a downwind forced landing, despite having an interstate highway and an open grass area short of the runway as available emergency landing sites.

The pilot not following his Pilot Operating checklist procedures. A factor was the aborted landing which interfered with the pilot's normal traffic pattern habit.