Factory 4.1 SL (slip-on)

Engineered as a racing system, the Factory 4 was a first in the industry.  The formed and tapered oval front endcap allows the muffler to be moved further forward in the frame, lowering the center of gravity and centralizing mass.  This “Factory Forward” engineering also allowed for packing material to be used in the space historically occupied by the midpipe.  This resulted in a shorter midpipe and overall muffler length to further centralize mass.  This ground-breaking design became the industry standard.  Many of the key features offered in the Factory 4.1 were derived from this muffler – the modular exhaust port flange and proprietary multi-layered packing material.  Combined with our exclusive Chamber Core and PowerBomb (full systems) technology, the Factory 4 utilizes our latest innovations to boost 4-stroke performance as well as improve handling.  The Factory 4 by FMF Racing….FEEL THE POWER!