On July 23, 2000, about 0830 eastern daylight time, a home built, unregistered aircraft, a two-place Quicksilver MXL Sport II, crashed while maneuvering in the vicinity of Clyo, Georgia. Visual meteorological conditions prevailed and no flight plan was filed. The aircraft was destroyed and the unlicensed occupant piloting the aircraft received fatal injuries. The flight originated from a private airstrip about 4 minutes before the accident. According to the owner/builder, he test-flew the newly constructed aircraft twice just before the accident flight for a total of 15 minutes. The accident pilot then took off and circled the airstrip three or four times before he flew over a wooded area and out of sight. When the noise of the engine abruptly stopped, the owner started searching and found the wreckage in a forested area. The owner/builder was advised by an FAA licensed mechanic/aircraft inspector on July 15, 2000, that the aircraft was "not safe for operation", and listed the following reasons; (1) the aircraft was modified by the installation of a 100 hp engine vs the designed 50 to 64 hp range, (2) The engine installation was of poor design and construction, (3) The propeller-to-spar clearance was 1 to 1.5 inches and made no allowances for propeller flexing, (4) the larger engine would contribute to a further aft center of gravity, possibly beyond aft CG limit, (5) fuel tank installation unsafe, (6) electrical wiring and connections unsafe, (6) battery mounting unsafe, (7) engine muffler mounting unsafe, (8) steel plate ballast mounting unsafe. A copy of the mechanic's statement is an attachment to this report. According to FAA inspectors, the aircraft was not registered or certified and did not meet the requirements of FAR Part 103 relating to ultralight aircraft. Neither the pilot nor the owner/operator held an FAA pilot's license. The owner/operator did not hold a waiver from the United States Ultralight Association or the Experimental Aircraft Association for ultralight flight instruction for the aircraft, nor was the pilot or owner/operator a registered ultralight pilot or instructor. Examination of the wreckage site revealed the aircraft came through the trees at a fairly steep angle, striking one branch about 60 feet high. The aircraft appeared to have rolled inverted somewhere between the first tree strike and terrain collision, and came to rest inverted. The right seat had been loaded with sand bags for ballast. Examination of flight controls revealed continuity and proper operation in all three axes. One blade of the carbon fiber, three bladed propeller was splintered about 1 to 2 inches from the tip, one blade was splintered at its half span, and the other blade, about 3 to 4 inches from the hub. The right wing trailing edge tube was severed and showed propeller paint transfer. The engine mount plate was secure to the main tube, and the two front engine mounts were secure; however, the engine had pulled loose from the two rear engine mounts due to stress failure of the rear engine mount washers. The rear mount bolts were still screwed tight, but the large rubber-sandwiched washers were cone shaped with wallowed out holes, suggesting stress failure due to terrain collision. The owner/builder stated that the pilot had remained lap belted into the left seat. Postmortem examination of the victim was performed on July 25, 2000, by Dr. Geoffrey P. Smith, M.D., Georgia Bureau of Investigations, Division of Forensic Sciences, Atlanta, Georgia. Cause of death was attributed to multiple blunt force injuries. Toxicological tests were conducted at the Federal Aviation Administration Research Laboratory, Oklahoma City, Oklahoma. Results of the tests include the following: (1) .008(ug/ml,ug/g) Tetrahydrocannabinol (marihuana) detected in blood (2) .012(ug/ml,ug/g) Tetrahydrocannabinol carboxylic acid detected in blood (3) .147(ug/ml,ug/g) Tetrahydrocannabinol carboxylic acid detected in urine (4) Meperidine present in blood (5) .014(ug/ml,ug/g) Meperidine detected in liver (6) .233(ug/ml,ug/g) Normeperidine detected in blood (7) 1.12(ug/ml,ug/g) Normeperidine detected in liver (8) .172(ug/ml,ug/g) Alpha-Hydroxyalprazolam detected in urine (9) Atenolol present in kidney and liver (10) Metoprolol detected in kidney and liver Meperidine, commonly known as Demerol, and its metabolite, normeperidine are prescription drugs used for the relief of acute pain, but can cause seizures if repeatedly dosed. Alpha-Hydroxyalprazolam is a metabolite of alprazolam, commonly known as Xanax, a prescription drug used for the management of anxiety and panic disorders. Atenolol and metoprolol are prescription drugs used to control high blood pressure.