Product Report: FMF Factory 4.1 RCT Exhaust



PRICE: $899.99

APPLICATION: All modern MX bikes (tested here on 2013 KTM 250SX-F)


The Factory 4.1 System incorporated the latest in FMF Resonance Chamber Technology both internally and externally. It starts with a new core – a patent pending shape enhances and refines the exhaust pressure wave for optimal power output while lowering the sound level. 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.┬áVisible changes to the exterior include a redesigned canister to increase internal capacity for the maximum volume of packing material. The packing itself was not overlooked - a proprietary blend formulated for superior durability and sound attenuation. The final component is a new rear endcap engineered for simple tuning adjustments incorporating a snap ring feature to secure the standard and optional inserts. 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.


-After we dropped the rear shock on our KTM to remove the stock exhaust system (yes, you really have to do this), the new FMF 4.1 RCT mounted up with complete ease.

-Once we pressed the button to fire up our orange machine, we instantly noticed a more throaty pitch to the exhaust.

-Out on the track, the transition from the mid to the top end power was smoothed out. The KTM motor was also able to rev more than before.

-The kit also came with a quiet insert, which will produce 94dB, and a spark arrestor.

-Being that this system is made out of titanium, we also noticed a weight savings.


– Although the 2013 KTM 250SX-F has the fastest stock motor in its class, it’s really sluggish off the bottom. Initially, we were hoping that a new exhaust system would help that lower end hit, but it was mildly improved.


The 2013 KTM 250SX-F came with an amazing stock exhaust system, but we knew that a new FMF Factory 4.1 RCT complete kit could help with the performance of our bike, which it did. The mid through top end power was increased, however, the bottom end only saw some slight improvements. Overall, we were completely pumped on our new pipe, and the new power we saw from it.