THE PILOT WAS CONDUCTING THE FLIGHT FOR THE PURPOSE OF GAME SPOTTING. THE PILOT LANDED THE AIRPLANE ABOUT 3/4THS DOWN A 800 FOOT LONG UNIMPROVED STRIP AND ELECTED TO GO-AROUND. DURING THE GO-AROUND, THE PLANE'S ENGINE EXPERIENCED A PARTIAL LOSS OF POWER, AND THE PILOT WAS FORCED TO LAND THE AIRPLANE ON A ROCK STREWN SURFACE. A SUBSEQUENT EXAMINATION OF THE PLANE'S ENGINE BY THE PILOT/OPERATOR DID NOT REVEAL THE CAUSE OF THE PARTIAL LOSS OF POWER.