One more question:

The engine ran fine for about flights, then about 5 minutes into the 5th flight, the engine conked out. Appears to be fuel starvation. Changed fuel tank, no help. A friend cleaned out carb, no help. Engine won't draw fuel on the ground when choked. Carb is a Tillotson with a serial number of S236C350.

Any suggestions or ideas? Thanks.

Steve