The amateur-built airplane departed on the cross-country flight with 12 gallons of fuel. The left and right wing tanks contained 5 and 7 gallons of fuel, respectively. The outbound flight leg was completed without any reported problems. The pilot did not refuel before departing on the return flight. On the return flight, about 8 miles from the destination airport, the airplane experienced a total loss of engine power. The pilot was unable to restart the engine and subsequently performed a forced landing into a forest clearing. The outboard half of the left wing was damaged during the landing when it impacted a tree. After the accident, the right fuel tank still contained 7 gallons of fuel. The left fuel tank was void of any usable fuel. Examination of the fuel tanks did not reveal any ruptures or breaches of any kind. The airplane was not equipped with a fuel tank selector. The output fuel lines for the right and left fuel tanks fed into a T-fitting which combined the fuel flow into a single line that serviced the engine. The output fuel lines from each tank were secured to airframe structural tubing with nylon cable-ties. The output fuel line from the right tank was pinched closed where one of the cable-ties was installed, restricting the fuel flow from the right tank. According to the pilot/builder, he finished installing wingtip navigation and strobe lights about 1.4 hours flight time before the accident. During the light installation, he routed and secured the associated electrical wiring in the same area as the fuel tank output lines. The pilot/builder stated that he may have tightened the fuel line cable-tie while he installed the navigation/strobe lights.