DURING A FLT FROM MADRAS, OR TO WALLA WALLA, WA, A LOSS OF ENG POWER OCCURRED DUE TO A FUEL FLOW PROBLEM & THE PLT MADE A SUCCESSFUL AUTOROTATION NEAR WARM SPRINGS, OR. A COMPANY MECHANIC WAS DISPATCHED TO THE HELICOPTER & HE REPAIRED A LOOSE FUEL LINE FITTING. LATE THAT EVENING, THE PLT STARTED & RAN THE ENG FOR ABOUT 10 MIN. HE THEN HOVERED FOR 4 TO 5 MIN BEFORE STARTING HIS DEPARTURE. THE PLT REPORTED THAT DURING DEPARTURE, THE ENG BEGAN LOSING RPM AT ABOUT 40 FT AGL. HE ATTEMPTED TO RESTORE POWER, BUT WAS UNABLE. SUBSEQUENTLY, THE HELICOPTER IMPACTED ON ITS SKID LANDING GEAR & TAIL SKID, THEN CAME TO REST ON ITS LEFT SIDE ABOUT 60 FT FROM THE IMPACT POINT. AN EXAM OF THE FUEL SYSTEM REVEALED THAT THE FUEL STRAINER, KOE/K2250B-2, WAS LOOSE AT BOTH ENGS OF THE GLASS & COULD BE TURNED WITH SLIGHT PRESSURE. THE BOLT AT THE BOTTOM OF THE LOWER PIECE WAS NOT SAFETY WIRED & WAS LOOSE.