FMF Exhaust - 44443 - Slip On Muffler - S/S with Carbon - Factory 4.1 RCT

The FMF Factory 4.1 RCT is a direct slip-on replacement for the standard muffler on the Yamaha YZ450F, WR450F and YZ450FX. It pairs an aluminium canister in a natural finish with a stainless steel midpipe and a carbon fibre end cap, and slips onto the standard head pipe.

FMF's Resonance Chamber Technology is applied both inside and outside the canister, allowing a shorter overall body that sits closer to the engine. That Factory Forward Engineering layout centralises mass and leaves less of the muffler exposed in a crash. The RTS (Rapid Tuning System) end cap arrangement makes it straightforward to swap inserts.

Built for motocross, enduro and off-road riders running a 450 four-stroke. This muffler is supplied for closed course competition use only and is not certified for Australian road use.

• FMF Resonance Chamber Technology applied internally and externally
• Shorter canister length, less exposed to crash damage than a full-length muffler
• Factory Forward Engineering positions the muffler closer to the engine to centralise mass
• RTS (Rapid Tuning System) for quick insert changes
• Aluminium canister in a natural finish with a carbon fibre end cap
• Stainless steel midpipe
• Screen-type spark arrestor insert included
• 94dB quiet insert included
• Slips onto the standard head pipe — single, slip-on configuration
• FMF states power gains across the rev range and weight savings over the standard muffler
• Manufactured at FMF's Southern California factory
• FMF part number 44443

• Factory 4.1 RCT slip-on muffler with stainless steel midpipe and carbon end cap
• Screen-type spark arrestor insert
• 94dB quiet insert

Let the exhaust cool completely before washing, handling or removing it — the canister, midpipe and carbon end cap hold heat well after the engine is shut down.
Plug the muffler outlet before washing the bike so water cannot soak the internal packing, and remove the plug before starting.
Clean with mild soap, water and a soft cloth. Keep degreasers, oven cleaner and abrasive pads away from the natural aluminium canister and the carbon end cap.
Wipe off mud, fuel spills and chain lube before the next ride; residue that is heat-cycled onto the canister will stain the natural finish permanently.
Repack the muffler with fresh glass-fibre packing when the exhaust note becomes noticeably louder or throttle response goes flat — saturated or blown-out packing raises sound output and hurts performance.
Check the midpipe clamp, mounting bolts and springs after the first ride and regularly after that; heat cycling and vibration will loosen fasteners.
Refit the slip joint clean and dry rather than sealing it with silicone, and take care not to over-tighten the clamp on the alloy canister.
Fit the supplied screen-type spark arrestor when riding in state forests, national parks or other fire-restricted areas where one is required by law.
Fit the 94dB quiet insert at tracks and riding areas that enforce a sound limit; it can be removed for closed-course use where noise limits allow.
Store the bike with the muffler dry — leaving wet packing to sit encourages corrosion inside the canister.
This muffler is supplied for closed course use only and is not certified for use on Australian public roads.