On June 2, 2018, about 1025 Alaska daylight time, a Piper PA-18-150 airplane, N624MW, sustained substantial damage during a forced landing, following a total loss of engine power near Lawrence Airstrip (55AK), Wasilla, Alaska. The airplane was registered to and operated by the pilot as a 14 Code of Federal Regulations (CFR) Part 91 visual flight rules flight when the accident occurred. The private pilot sustained serious injuries. Visual meteorological conditions prevailed, and no flight plan had been filed. The flight departed 55AK about 1023 destined for Big Lake, Alaska. According to the pilot, shortly after departure from 55AK, all engine power was lost. There were no sights or sounds consistent with a catastrophic engine failure and the engine ceased operation consistent with fuel starvation. The pilot reported the left fuel tank was about ½ full, the right fuel tank was empty, and the fuel selector was on "BOTH.". During the forced landing, the pilot attempted to return to the runway, but impacted a forested area of tall spruce and birch trees, resulting in substantial damage to the wings and rudder. On July 11, 2018 the engine, a Lycoming O-320-A2B, was examined at Alaska Claims Services under the supervision of the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) and another NTSB investigator. Prior to removing the engine from the airframe, the gascolator was drained and small amounts of unidentified contaminants were found. The carburetor bowl was then drained with more minute contaminants present. The engine was then removed from the airframe and transported to Alaska Aircraft Engines, Anchorage, Alaska where it was attached to an engine test truck on July 17. A four bladed wooden club propeller was installed for the test run. The engine started within 3 seconds and was warmed at idle power for 5 minutes. The engine RPM was set at idle and maximum power for 5 minutes each followed by rapid manipulations from idle to maximum continuous power. No hesitations or anomalies were observed throughout the engine run.