P J Motorcycle Engineers LTD Yamaha TZR 250 Boyesen Reed Valves

Boyesen developed and patented the dual-stage reed. The dual-stage design incorporates a highly responsive top reed placed on top of a stiffer, ported reed for superior performance throughout the entire powerband. The top reed is lightweight and resilient for crisp throttle response at partial throttle or low RPMs. The stiffer, bottom reed is ported to provide maximum flow and horsepower at higher RPMs. Dual-stage reeds work in unison to perform efficiently throughout the entire powerband. The difference in stiffness between the top reed and the bottom reed allows the reeds to respond quickly and accurately to changes in engine pressure as you accelerate or back off the throttle. This translates into a dramatic increase in engine efficiency and performance across the entire powerband, from start-up to wide open throttle.