The Factory 4.1 is FMF Racing’s premier performance exhaust. With over 35 years of racing experience behind it, the Factory 4.1 takes advantage of everything we’ve learned on the race track. The Factory 4.1 is guaranteed to produce more horsepower throughout the entire RPM range. More power means better starts and less work getting around the track. Reduced weight means better handling resulting in less fatigue at the end of a moto. If performance is your priority, the Factory 4.1 is the only exhaust for you.
Horsepower gains throughout RPM range
Advanced engineering and patented design
Meets AMA/FIM 94dB sound requirement
Spark arrestor available for purchase
Used by Factory KTM, Yamaha of Troy, JGR and Star Racing
Use with FMF or stock header
Easily serviced for repacking
FACTORY 4.1C
By giving the Factory 4.1 a carbon fiber shell, we made the world’s best performing exhaust the world’s lightest exhaust. The Factory 4.1 Carbon utilizes the same cutting edge technology as the titanium version. This exhaust doesn’t just look Factory–it feels Factory. If you want the lightest and best performing exhaust available, the Factory 4.1 Carbon is for you.
The lightest full system available
Aerospace grade materials, highest quality used in the off-road market
Race tested for proven reliability and performance
94dB insert included
Spark arrestor available
Comes with titanium midpipe and exclusive repack indicator
