Yamaha - Oil Tank Assembly Oil Injection System 6E5-21750-05-00. Overview. On oil-injected Yamahas, the oil tank is one of those parts you don't think about until something feels off-or worse, an alarm goes off. This assembly keeps a steady supply of oil moving to your engine, which is critical for keeping everything lubricated and running clean. Over time, tanks can get brittle, sensors can act up, or connections start to fail. Swapping in a solid, reliable oil tank assembly helps keep your sys