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 the moto. If performance is your priority, the Factory 4.1 is the only exhaust for you.
Features:
- Massive power gains throughout the RPM range
- Huge weight savings
- New RTS (Rapid Tuning System)
- Advanced engineering and patented design
- Meets AMA/FIM 94dB sound requirement
- Spark arrestor available for purchase
- Used by BTO Sports KTM, JGR Toyota Yamaha, NFab Yamaha, Rockstar Energy Racing KTM
- Use with FMF or stock header
- Easily serviced for repacking
