The science behind this new Yoshimura RS-4D exhaust sounds simple — two holes are larger than one and that increased outlet area flows burnt hydrocarbons easier. But, in addition to the boost in top-end horsepower typically associated with freer-flowing exhausts, Yoshimura is also claiming increased low-rev torque. Regardless, it’s the unique two-outlet looks that make the RS-4D stand out.
Developed for use on Ryan Dungey’s Supercross RM-Z450, the full-titanium system is also available for the Suzuki RM-Z250, Honda CRF450R and CRF250R. Both titanium and carbon canisters are available, but both come with carbon endcaps.