V-Force (VF4) Yamaha YFS200 Blaster All years The reed valve system V-FORCE4 has been developed on the solid base of V-FORCE3, to which many enhancements have been made. The carbon fibre reed petals combined with the new resin frame boost the velocity of your machine, thanks to an airflow 10% better than the first fit. The V-FORCE4 arosystem is fitted with external walls covering and protecting the reed petals and prolonging their longevity.