Yamaha Clutch Boss – R15 / MT15

The Yamaha Clutch Boss (R15 / MT‑15) is a key internal component of the clutch assembly. It serves as the hub around which the friction and steel clutch plates are stacked, keeping the clutch basket and pressure plates properly aligned. This ensures efficient transmission of engine power to the gearbox and rear wheel when the clutch is engaged.

In sport bikes like the R15 and MT‑15, which use an assist and slipper clutch system, the clutch boss plays a critical role. It allows firm clutch engagement with lighter lever effort during acceleration while enabling controlled slip during aggressive deceleration or downshifts. This reduces engine‑braking shock and prevents rear-wheel lockup.

A properly manufactured clutch boss ensures smooth clutch operation, maintains alignment of clutch plates, and resists wear under load. Over time, a worn or damaged boss can lead to clutch slippage, rough shifting, reduced performance, or clutch failure. Replacing the clutch boss restores reliable clutch function, smooth gear changes, and consistent engine power transfer.