Yoshimura · RS-12
The Yoshimura Sound Insert Kit RS-12 Muffler, 1.500" is a replacement low-volume insert kit designed for Yoshimura RS-12 mufflers. This kit is listed for Yamaha YZ450F 2026–2027 fitment (see the fitment table below) and is intended for riders who need a different sound restriction setup for their specific application.
Offered as an optional kit on applications requiring different sound restrictions, this insert can be used to tune the exhaust note to match the needs of the bike and riding environment. Decibel reduction depends on application, and fitment should be confirmed using the insert chart referenced on the page.
Sound
Built specifically as a replacement service part for Yoshimura RS-12 mufflers, this sound insert kit is intended to restore or adjust an RS-12 setup without changing the muffler itself. It is also offered as an optional kit where different sound restrictions may be required.
Installation
This kit is identified as non-spark arrested. For riders selecting an insert based on event requirements or riding location rules, it is important to confirm the correct insert option for the intended application before installation.
Included
The kit includes the key components needed for installation: a low-volume insert tube, an end-cap collar, and a set screw. With the correct parts included, it supports straightforward replacement of the insert components on compatible RS-12 muffler applications.
Sound
As part of Yoshimura’s Replacement Service Parts product line, the INS-39-K kit is designed to serve as a direct low-volume insert solution for RS-12 mufflers. It can be used as a replacement insert kit or as an optional choice on applications where different sound restrictions are required, helping tailor the exhaust setup without replacing the full muffler.
Fitment
This sound insert kit is listed for Yamaha YZ450F 2026–2027. Because insert compatibility can vary by application, fitment should be verified before purchase and installation. Reference the insert chart on the page and the fitment table below to confirm the correct match for the intended bike and RS-12 muffler configuration.
Installation
Yoshimura notes that decibel reduction depends on application, so sound output changes will vary by how the muffler is configured and used. An installation PDF is provided on the page to support proper assembly and fit, using the included low-volume insert tube, end-cap collar, and set screw.
| Part Number | INS-39-K |
|---|---|
| Brand | Yoshimura |
| Product Line | Replacement Service Parts |
| Series | RS-12 |
| Shipping Weight | 0.25 lb |
| Barcode | 00840025917903 |
| Make | Model | Model Years |
|---|---|---|
| Yamaha | YZ450F | 2026–2027 |
Fitment as listed by Yoshimura for part number INS-39-K.
Instructions / What's Included (PDF)
Provided by Yoshimura. Opens in a new tab.
