The FMF Factory 4.1 RCT Aluminum Slip-On Muffler is engineered for select Yamaha YZ450F and YZ450FX motorcycles. Manufacturer part number 044443 and vendor part number 79-40636 identify this application-specific exhaust component. It uses FMF Resonance Chamber Technology to reduce sound levels while maintaining strong power output, making it a practical performance upgrade for riders seeking refined exhaust characteristics and durable trail or track functionality.
The patented core shape, canister design, and chamber configuration work together to improve sound absorption and refine exhaust pressure. Factory Forward Engineering centralizes the muffler mass to help reduce exposure to crash damage, while application-specific core specifications provide a tuned exhaust configuration for compatible Yamaha models. The aluminum canister is paired with a stainless-steel mid-pipe, and the rear end cap is designed for straightforward installation of tuning tip inserts or the included spark arrestor.
Feature: FMF Factory 4.1 RCT slip-on muffler with aluminum canister and stainless-steel mid-pipe.
Feature: Resonance Chamber Technology helps lower sound output while preserving maximum power potential.
Feature: Patented canister shape provides additional internal volume for sound-absorbing material.
Feature: Factory Forward Engineering helps centralize mass and reduce vulnerability to crash damage.
Feature: Includes a spark arrestor and wash plug.
Feature: Designed for direct fitment on select 2018–2023 Yamaha YZ450F models and 2019–2022 Yamaha YZ450FX models.
Fitment includes the 2018 through 2023 Yamaha YZ450F, plus the 2019 through 2022 Yamaha YZ450FX, subject to the specific model year and configuration. Verify the motorcycle application before installation. This FMF exhaust component is manufactured by FMF and supplied under manufacturer part number 044443 and vendor part number 79-40636.
Features:
- FMF Factory 4.1 RCT slip-on muffler with aluminum canister and stainless-steel mid-pipe
- Resonance Chamber Technology lowers sound output while maintaining strong power potential
- Patented core shape and chamber design refine exhaust pressure
- Patented canister shape increases internal volume for sound-absorbing material
- Factory Forward Engineering centralizes mass and helps reduce crash damage exposure
- Application-tuned core specifications for compatible Yamaha motorcycles
- Rear end cap supports installation of tuning tip inserts or a spark arrestor
- Includes spark arrestor and wash plug
- Fits select 2018–2023 Yamaha YZ450F and 2019–2022 Yamaha YZ450FX models
- Manufacturer part number 044443; vendor part number 79-40636
Fitment:
2018 Yamaha YZ450F
2019 Yamaha WR450F
2019 Yamaha YZ450F
2019 Yamaha YZ450FX
2020 Yamaha WR450F
2020 Yamaha YZ450F
2020 Yamaha YZ450FX
2021 Yamaha WR450F
2021 Yamaha YZ450F
2021 Yamaha YZ450FX
2022 Yamaha WR450F
2022 Yamaha YZ450F
2022 Yamaha YZ450FX
2023 Yamaha WR450F
2023 Yamaha YZ450F
2023 Yamaha YZ450FX
2024 Yamaha WR450F
2024 Yamaha YZ450F
2024 Yamaha YZ450FX
2025 Yamaha WR450F
2025 Yamaha YZ450F
2025 Yamaha YZ450FX
2026 Yamaha WR450F
2026 Yamaha YZ450F
2026 Yamaha YZ450FX