• Horsepower gains throughout RPM range
• Advanced engineering and patent pending design
• Meets AMA 99dB sound requirement
• Used by Factory KTM, Yamaha of Troy, MDK Racing and Star Racing

The Factory 4.1 is FMF Racing’s premier performance exhaust. With 30 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.