Description

The Factory 4.1 RCT incorporates the latest in FMF Resonance Chamber Technology™ both internally and externally. In addition, we achieve a shorter overall length that is less susceptible to crash damage and complementary to our Factory Forward Engineering – moving the muffler closer to the motor to centralize mass. The Factory 4.1 RCT is constructed from only aerospace grade materials that meet our exacting specifications and is manufactured 100% at our Southern California factory.
- Available in Natural Aluminum Muffler with Carbon End Cap
- Massive Power gains throughout the RPM range.
- Huge weight savings
- New RTS (Rapid Tuning System)
- FMF uses the highest quality proprietary blend of alloy grade titanium made especially to our standards.

![4.1 RCT S/S YZ450F 2018-19 Full System w/carb end cap []](https://boydsassets.specd.nz/uploads/2026/09/60ebd56f-44ef-4bff-a3ab-41f8a2699a6b-jpg.webp)
![4.1 RCT S/S YZ450F 2018-19 Full System w/carb end cap []](https://boydsassets.specd.nz/uploads/2026/09/41cb3c43-23c8-46ba-8053-1bb162dd95b0-jpg.webp)
![4.1 RCT S/S YZ450F 2018-19 Full System w/carb end cap []](https://boydsassets.specd.nz/uploads/2026/09/bd129e50-e699-46bd-a8b6-97153cd944a1-jpg.webp)
![4.1 RCT S/S YZ450F 2018-19 Full System w/carb end cap []](https://boydsassets.specd.nz/uploads/2026/09/08f38ff5-4795-4499-a384-435b40403d17-jpg.webp)
![4.1 RCT S/S YZ450F 2018-19 Full System w/carb end cap []](https://boydsassets.specd.nz/uploads/2026/09/c3fe0593-7207-4325-85f6-27c0941184f6-jpg.webp)




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