Yamaha Fuel Tank Assembly 99999-03861-00. Overview. The Yamaha Fuel Tank Assembly 99999-03861-00 is a genuine original equipment manufacturer component designed to safely store and supply fuel to your engine. This complete assembly is engineered to maintain consistent fuel delivery while protecting against leaks, contamination, and fuel evaporation.. A reliable fuel tank is essential for maintaining engine performance and efficiency. Over time, tanks can degrade due to fuel exposure, environment