V-Force 4 Yamaha YZ 125 05-07 Reed Valve Assembly

The all-new VForce4 is built upon the solid foundation that has made the VForce3 such a success for the last 10 years. While the VForce3 has been continually refined over the years, this is a complete redesign of the entire system. All the components that go into making a VForce reed valve system have been significantly changed since the VForce3. The unique design of the VForce reed valve system features double the reed tip surface over a conventional reed valve design. This has two major benefits: 1) The reed petals only travel half the distance as a conventional reed valve design to get the same airflow. 2) Because the reed petals only need to travel half the distance of that on a conventional reed valve design, there is a greater chance of them being fully opened as well as a better chance of sealing when they are "closed". A reed petal never truly "closes" in a classic sense, as it is always in movement. Consider this, an engine operating at 8,000 RPM results in a reed petal opening and closing 133 times in one second. This fact, sheds light on another VForce advantage. Since the petals are only traveling half the distance, they generally last longer are they receive less wear than the reed petals on a conventional reed valve design.