The term identifies an aftermarket performance upgrade package designed for the Yamaha Banshee all-terrain vehicle. It typically includes larger displacement cylinders, pistons, and supporting components intended to increase engine size to 421cc. This modification alters the stock engine configuration to achieve enhanced power and torque output.
This enhancement offers increased acceleration, improved hill-climbing ability, and greater overall performance compared to the standard engine. Historically, such upgrades became popular as enthusiasts sought to maximize the capabilities of the Banshee, a two-stroke ATV known for its inherent power potential. It represents a significant investment aimed at transforming the vehicle’s performance characteristics.