This Factory 4.1™ Muffler incorporates the latest FMF
Resonance Chamber Technology®. The patented chamber
design enhances and refines exhaust pressure. Its patented
core shape lowers sound level while maintaining maximum
power output, and the patented canister shape increases
internal volume for more sound-absorbing material. Factory
Forward Engineering centralizes mass and is less prone to
impact damage. Used by the AmPro™ Yamaha Racing Team.
Maintenance is made easy with the removal of four screws
on the front end cap, and the innovative rear end cap
simplifies installation of the spark arrestor (sold separately)
or tuning tip inserts. Includes QuietCore™ 94 dBA insert.
Meets AMA® and FIM sound requirements. Compatible with
stock or FMF® header. Built 100% in the U.S.A.Note: YZ models are for closed-course use regardless of modification.
