Boyesen's patented dual-stage reed design incorporates a specially shaped top reed and a ported bottom reed. 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.
Fits: Yamaha IT250 1981-1983 YZ250 1989 YZ490 1982-1983