FMF's Factory 4.1 SL slip-on muffler is guaranteed to produce more horsepower throughout the entire RPM range when compared to the stock muffler. Each Factory 4.1 SL muffler is constructed from only aerospace grade materials that meet the California company's exacting specifications.
Massive power gains throughout the RPM range
Significant weight savings when compared to the stock muffler
Fabricated using the highest quality alloy grade materials
Fits OEM or FMF headers
Comes with all required mounting hardware and easy-to-follow installation instructions
FMF 94 dB quiet insert available (sold separately)
Made in the USA
Product Note:
Specification
Details
Color
Varies (make selection above)
Configuration
Single Muffler
Country of Origin
USA
Finish
Varies (make selection above)
Mid-Pipe
Varies (make selection above)
Muffler End Cap
Stainless Steel
Muffler Sleeve
Titanium
USFS Approved Spark Arrestor
Varies (make selection above)
Vehicle Fitment
Fitment is guaranteed or your money back plus free return shipping.
Don’t waste time installing a product that doesn't fit. We worked hard ensuring that this product is an exact fit on the vehicles listed below.
Honda
CRF150R 2007-2009, 2013-2024
Yamaha
Raptor 700 2013-2023
Raptor 700R 2006-2023
WR250F 2007-2013
WR450F 2007-2011
YFZ450 ATV 2004-2009, 2012-2013
YZ250F 4-Stroke 2006-2010
YZ450F 2006-2009
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Questions & Answers
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