DURING GROUND ROLL, WITNESSES REPORTED ENG DEVELOPING INTERMITTENT POWER. TAKEOFF CONTINUED & AT ABOUT 150 FEET AGL. PLT INITIATED A TURN TO THE LEFT TO RETURN TO THE ARPT.DURING THE TURN ACFT STALLED & CRASHED ON ARPT PROPERTY. PLT WAS REMOVED FROM BURNING ACFT & TRANSPORTED TO THE HOSPITAL WHERE HE DIED OF HIS INJURIES. FIRE EXTINGUISHED BY LOCAL FIRE DEPT. EXAM OF ACFT REVEALED NO EVIDENCE OF FAILURE OR MALFUNCTION OF THE FLT CONTROLS. EXAM OF ENG REVEALED NO DETERMINATION COULD BE MADE FOR THE REPORTED INTERMITTENT POWER. THE IGNITION HARNESS & LT MAGNETO WERE DAMAGED BY FIRE. RT MAGNETO OPERATED NORMALLY, AS DID THE SPARK PLUGS. MAGNETO SWITCH AT ACCIDENT SITE POSITIONED TO THE RT MAG. IT TESTED NORMALLY. FUEL CONTINUITY FROM EACH FUEL TANK TO GASCOLATOR WAS VERIFIED. FUEL LINE FROM GASCOLATOR TO CARBURETOR WAS DAMAGED BY FIRE. EXAM OF CARBURETOR REVEALED FLOAT DESTROYED & PRIMARY VENTURI NOT INSTALLED. IDENTICAL ENG AT MANUFACTURERS FACILITY WITH VENTURI REMOVED FROM CARB REVEALED NO DEGRADATION OF ENG PERFORMANCE.