Yamaha - Check Valve Assembly Fuel System 6E5-11370-01-00. Overview. Check valves are one of those small parts that can cause big headaches when they stop working right. They're there to keep fuel or air moving in the correct direction, and when they fail, you'll notice it in how the engine runs. I've seen motors struggle with starting or lose consistency just because a valve wasn't holding pressure. Swapping it out is a simple fix that helps restore proper flow and reliable performance.. Key Features. One-Way Flow Control - Ensures fuel or air moves in the correct direction without backflow.. Maintains System Pressure - Helps keep consistent pressure for smooth engine operation.. Durable Internal Components - Built to handle constant cycling and fuel system exposure.. OEM Precision Fit - Matches original specifications for proper installation and function.. Engine & Boat Compatibility. Designed for Yamaha 2-stroke outboard engines with fuel and air delivery systems that use check valv