WHILE RIDING THROUGH CHANGING ELEVATIONS, THE FUEL SYSTEM MALFUNCTIONS WHILE APPLYING THROTTLE BELOW 4,000 RPM. ESPECIALLY PREVALENT WHEN LOAD APPLIED NEAR IDLE SPEED. WHILE TRYING TO PERFORM A LOW SPEED MANEUVER (PULLING IN TO A GRAVEL PARKING LOT), THE ENGINE ACTED AS IF IT WAS GOING TO STALL, THEN CAUGHT SUDDENLY, RESULTING IN A FALL. *TR