Yamaha Xmax 300 Crankshaft Assy (B74-E1400-10)

The Yamaha XMAX 300 Crankshaft Assembly (B74-E1400-10) is a fundamental engine component that converts the up-and-down motion of the piston into rotational motion that drives the transmission and final drive. Machined to precise tolerances and balanced for smooth operation, this assembly includes the main crank journals, connecting rod journals, and counterweights necessary for proper dynamic balance.

Built to Yamaha’s original specifications, the crankshaft assembly is engineered from high-strength forged steel to withstand the forces of combustion, high engine speeds, and sustained heat. Over time, wear, fatigue, or damage to bearings and journals can lead to excessive play, noise, vibration, and reduced engine performance. Replacing a worn or damaged crankshaft assembly with this genuine-style unit restores correct rotational geometry, reduces vibration, and helps ensure consistent power delivery and engine longevity.

Because it is central to engine operation, the crankshaft assembly plays a key role in engine reliability, smoothness, and performance. Proper installation and correct bearing fitment are essential for maintaining proper clearances, lubrication, and long service life.