At approximately 21:45 mountain time, a Cessna 172K crashed when it struck the water during takeoff from a beach near Orchard. The pilot was not injured. The flight originated at Greeley, Colo., at approximately 18:30. The pilot said extensive maintenance had been performed on the airplane and on two different occasions he had made off-airport precautionary landings due to smoke in the cockpit. In the first incident, wiring inside the transponder had burned. In the second incident, unsecured wires had chafed against a bus bar and short-circuited. On the accident flight, the pilot saw smoke coming from the cowling and a light smoke entered the cockpit. He elected to make a precautionary landing on a beach alongside the Riverside Reservoir. After landing, the pilot inspected the airplane and concluded that the breaking in of the newly installed muffler and exhaust stacks was the most likely source of the smoke. He made a short field takeoff but the right wing dropped and the airplane struck the water and nosed over.