A BEECH 65 COLLIDED WITH TREES IN MOUNTAINOUS TERRAIN AFTER AN INFLT LOSS OF CONTROL. A PILOT OBSERVED THE AIRPLANE START A TURN TO THE RIGHT, ROLL RIGHT AND CONTINUED UNTIL INVERTED AND ENTER INTO A SPIN. THE ACFT WAS IN A STEEP NOSE DOWN ATTITUDE WHEN IT BEGAN ITS PULL; OUT. THE ENGINES WERE HEARD BY A GROUND WITNESS WHO INITIALLY MISTOOK THEM FOR AN APPROACH MOTORCYCLE. THE PILOT INITIALLY FLEW THE ACFT 45 DAYS BEFORE THE ACCIDENT AND LOGGED 3.5 DUAL INSTRUCTION HOURS. THERE WAS NO RECORD IN THE PILOT'S LOGBOOK OF ANY ADDITIONAL FLT TRNG SINCE THE INITIAL FLT. THE PLT SATISFACTORILY COMPLETED A BFR IN A CESSNA 150 FOUR DAYS BEFORE THE ACCIDENT. EXAM OF THE WRECKAGE DSCLSD THE RT ENG HAD BROKEN EXHAUST VALVE, BUT THE LEFT PROP WAS FEATHERED. THERE WERE NO PREEXISTING MECH MALFUNCTIONS OR FAILURES FOUND WITH THE LEFT ENG.