THE PILOT WAS ON THE BASE LEG FOR LANDING ON THE KENAI RIVER WHEN THE ENGINE STOPPED PRODUCING POWER. HE WAS UNABLE TO GLIDE TO THE RIVER SO HE LANDED ON A ROAD. DURING THE FORCED LANDING SEQUENCE THE AIRPLANE STRUCK SOME TREES BEFORE LANDING ON THE ROAD. EXAMINATION OF THE AIRPLANE AND ENGINE SHOWED NO MECHANICAL MALFUNCTION. THE PILOT STATED HE FELT IT WAS CARBURETOR ICE WHICH CAUSED THE POWER LOSS. HE WAS CARRYING ONLY 15 INCHES OF MANIFOLD PRESSURE DURING THE MANEUVERING AND TRAFFIC PATTERN AND HAD APPLIED CARBURETOR HEAT. HE DID NOT KNOW IF THE CARBURETOR HEAT WAS OPERATING.