Yoshimura · RS-12
The Yoshimura SOUND INSERT KIT RS-12 Muffler, 1.250" (INS-33-K) is a replacement low-volume insert kit designed for RS-12 mufflers. It is intended for riders who need an optional insert solution on applications that call for different sound restrictions, while staying within the RS-12 family of components.
This kit fits select Honda, Kawasaki, Triumph, and Yamaha models as listed in the fitment table on the page. Decibel reduction varies by application, so confirming the correct application is important before installation. An installation PDF is provided on the page for reference.
Built as a replacement low-volume insert kit for Yoshimura RS-12 mufflers, INS-33-K provides an insert option for riders needing a different sound restriction setup. Because results vary by motorcycle and configuration, decibel reduction depends on the specific application being used.
This insert kit is specified as non-spark arrested. That detail matters when choosing components for a particular riding area or requirement, so it is recommended to confirm insert selection and application needs before installation using the insert chart referenced on the page.
INS-33-K ships as a complete kit with the key pieces needed for installation: a low-volume insert tube, an end-cap collar, and a set screw.
Sound
Yoshimura positions this component within its Replacement Service Parts product line for the RS-12 series. The INS-33-K kit is intended specifically as a low-volume insert solution for RS-12 mufflers, offering an optional configuration for applications that require different sound restrictions. Since sound output changes can vary depending on the motorcycle and setup, the manufacturer notes that decibel reduction depends on the application.
Fitment
Fitment for the INS-33-K insert kit is limited to the models and model years shown in the fitment table, including select Honda, Kawasaki, Triumph, and Yamaha applications. Yoshimura also advises using its insert chart to confirm the correct match for the intended application. Reviewing those resources before purchasing or installing helps ensure the correct RS-12 insert configuration is selected for the motorcycle.
Installation
This kit includes the low-volume insert tube, end-cap collar, and set screw, making it a straightforward replacement insert package for an RS-12 muffler. For installation guidance, the page provides an installation PDF to reference during setup. Verifying application details beforehand is recommended, especially because expected decibel reduction and requirements can vary by the specific fitment.
| Part Number | INS-33-K |
|---|---|
| Brand | Yoshimura |
| Product Line | Replacement Service Parts |
| Series | RS-12 |
| Shipping Weight | 1 lb |
| Barcode | 00840025914308 |
| Make | Model | Model Years |
|---|---|---|
| Honda | CRF450R | 2025–2026 |
| Honda | CRF450RX | 2025–2026 |
| Kawasaki | KX250F | 2021–2024 |
| Kawasaki | KX250X | 2021–2024 |
| Triumph | TF250 | 2024–2026 |
| Yamaha | WR250F | 2023 |
| Yamaha | YZ250F | 2019–2020 |
| Yamaha | YZ450F | 2026–2027 |
Fitment as listed by Yoshimura for part number INS-33-K.
Instructions / What's Included (PDF)
Provided by Yoshimura. Opens in a new tab.
