Yamaha - Woodruff Key Engine Timing Component 90280-04M05-00. Overview. A woodruff key is one of those parts that seems minor right up until it fails. I've seen flywheels and timing-related components slip just enough to cause hard starting, rough running, or bigger internal headaches. The Yamaha Woodruff Key 90280-04M05-00 is there to keep critical rotating parts locked in position so everything stays indexed the way Yamaha intended. It's a small, inexpensive part, but it protects a whole lot o