Yoshimura Sound Insert Kit INS-14-K | Yoshimura RS-4 Muffler 1.50-Inch | 94dB Rated

The Yoshimura Sound Insert Kit INS-14-K is a 94dB-rated low-volume insert for Yoshimura RS-4 mufflers with a 1.50-inch outlet, reducing measured exhaust noise so the same system can run at sound-restricted tracks and race events.

The 94dB figure is the point of this part. Most AMA-sanctioned motocross and off-road events, and a large number of private tracks, enforce a sound limit measured at a set distance and rpm — and a bike that fails is not allowed to race. Fitting a rated insert is the difference between a start gate and a long drive home.

This is a sound insert, not a spark arrester. It reduces noise but does not satisfy US Forest Service or BLM requirements, which need an approved arrester instead. Riders who need both should fit an arrester as well.

• 94dB rated low-volume sound insert
• 1.50-inch size, for Yoshimura RS-4 mufflers
• Brings measured sound level down for sound-tested race events
• Fits and removes without muffler disassembly
• Not a spark arrester — does not satisfy USFS or BLM requirements
• Yoshimura part number 961-9005 (manufacturer part INS-14-K)

Essential kit for anyone racing a Yoshimura RS-4 equipped machine at sound-tested motocross or off-road events. Confirm your muffler outlet is the 1.50-inch RS-4 size before ordering, and check the specific dB limit your series enforces — Yoshimura offers inserts at more than one rating.