Yoshimura RS4 Quiet Insert

  Engineered for the CRF 300L Yoshimura RS4 muffler, this quiet insert delivers measurable noise reduction without sacrificing performance. Compatible with or without the Yoshimura spark arrestor, it achieves approximately a 6dB reduction at idle and 5500RPM—translating to roughly 30% perceived sound pressure reduction. Due to the logarithmic nature of the decibel scale, this modest technical decrease produces a substantially quieter riding experience. The insert maintains the system's power delivery while making it significantly more refined and street-friendly.