Yamaha Flywheel Shaft Gear 7X9-11972-00-00. Overview. The Yamaha Flywheel Shaft Gear 7X9-11972-00-00 is a genuine original equipment manufacturer component designed to ensure precise mechanical synchronization within your engine. This gear plays a critical role in transferring rotational motion from the flywheel shaft to connected engine components, helping maintain proper timing and smooth operation.. Accurate gear engagement is essential for engine efficiency and longevity. Over time, gears ca