Yamaha YFZ350 Banshee (1988-2007) V-Force Reed Valve System

Yamaha YFZ350 Banshee (1988-2007) V-Force Reed Valve System

Building on the solid foundation of the VF3, the VF4 has been enhanced with a range of improvements designed to optimise performance. The carbon fibre reed petals, combined with a new resin frame, significantly increase airflow—boosting it by 10% compared to the standard system—delivering improved velocity and performance. Additionally, the VForce4 features external walls that shield and protect the reed petals, prolonging their durability.

Unique VForce Reed Valve Design

The VForce reed valve system offers double the reed-tip surface area of conventional reed valve designs, delivering two key benefits:

• Reduced Reed Petal Travel: The reed petals only need to travel half the distance of those in a conventional system to achieve the same airflow.
• Improved Performance and Durability: Reduced travel increases the likelihood of full petal opening and effective sealing when “closed.” While reed petals never fully close due to constant movement, their reduced motion in the VForce system minimises wear, extending their lifespan.

For context, at 8,000 RPM, a reed petal opens and closes 133 times per second. With the VForce design, less travel means significantly less stress and wear on the petals.

Standard VForce Reed Valve Features:

• Double the reed-tip surface of conventional designs.
• Increased bottom-end power, stronger mid-range, and extended top-end performance.
• Improved efficiency due to reduced reed petal travel.
• Increased airflow for greater horsepower.
• Reduced reed petal wear.
• Screw-free design eliminates the risk of screws entering the motor.
• Screw-free design allows quick and easy reed petal changes.

New and Improved VF4 Features:

• All-new reed petal resin system with carbon fibre construction and optimised lay-up.
• Pre-curved reed petals for improved sealing at the tip.
• Wider reed cage for maximum airflow.
• 10.5% increase in combined reed tip area, delivering enhanced overall airflow.
• Airfoil-shaped cage tips to boost air velocity from the outer ports.
• Long reed stops to progressively slow petal tip velocity, increasing durability.
• 15.6% reduction in the frontal area of the central wing, combined with a more aerodynamic shape.