On January 16, 2001, at 0915 eastern standard time, a Lake LA-4-200, N12E, experienced a flash explosion while the pilot attempted to start the engine at the Orlando Executive Airport in Orlando, Florida. The personal flight was operated by the pilot under the provisions of Title 14 CFR Part 91 with no flight plan filed. Visual weather conditions prevailed at the time of the explosion. The airplane sustained substantial structural damage. The private pilot and his passenger were not injured. The explosion occurred during the first engine start of the day at 0915. The pilot stated he did not detect any fumes prior to engine start. He reported draining the hull as recommended to remove any accumulated water and fuel vapor after the previous flight. The engine turned over twice before the explosion occurred. The examination of the airplane revealed the explosion occurred in the rear cabin area of the airframe. Blue fuel stains were found on fuel lines and fittings inside the enclosed fuel system compartments. A crack was found on a fuel block fitting of the fuel drain assembly. The main fuel tank and associated fuel components are in close proximity to the battery installation. During the post-accident examination of the airplane, corrosion was discovered on the battery grounding strap. The annual inspection was completed on October 20, 2000, about three months before the accident. Section D, item 2, of the Lake-4-200 Maintenance Inspection Procedures states "Check battery , box and cable (check at least every 30 days). Section D, item 7, states, "check fuel lines, valves and gauges for damage and operation" of the airplane includes checking the battery and ground strap for corrosion and the fuel system and fittings for leaks. No record of the ground strap inspection was discovered.