A fuel introducing member is connected to an opening end of a siphon pipe forming a fuel tank. The fuel introducing member has an opening for introducing fuel within the tank, and the opening is formed in the upper surface of a cover section. A lid body is pivotably mounted to the upper surface. When the opening is above the level of fuel, the lid body closes the opening by the weight of the lid body, and when the opening is below the level of the fuel, the lid body floats in the fuel to open the opening. The opening is located below the upper end of the inner diameter of the opening end of the siphon pipe.