Performance Muffler Cover – Fits Stihl 661

Engineered for increased power and improved engine cooling, this high-performance exhaust cover is precision CNC machined from 6061-T6 billet aluminum, a high-strength, aerospace-grade alloy known for excellent heat dissipation and durability. Built for demanding conditions and proudly made in the USA.

Compatible Models:

STIHL MS 661

Outlet Direction (Facing Bar or Facing Recoil):

Facing Bar means the exhaust outlet points toward the guide bar side of the saw. Facing Recoil means it points toward the pull-start side. This is strictly operator preference and has no effect on performance.

What's Included:

One-piece exhaust cover, spark arrestor screen with aperture size compliant with USFS specifications, high-temperature gasket, complete hardware kit, and Loctite 243 Threadlocker (0.5 ml bottle).

Dyno Proven Performance:

Tested on a completely stock saw with no modifications other than the exhaust cover. Results showed a 6.21% increase in horsepower and a 9.92% increase in torque.

Performance gains will vary depending on the saw and the level of modification.

Installation Notes:

• Post-installation tuning or recalibration is required for optimal performance.

• Apply the supplied threadlocker to all mounting screws and torque to the values specified in the installation instructions. Retorque after the first few heat cycles and periodically check torque as part of routine maintenance.

Exhaust Sound:

Increased exhaust noise is expected compared to the factory exhaust. Proper hearing protection is essential and should always be worn.

Terms & Safety Disclaimer: Proper installation, engine tuning or recalibration, hardware torque, and periodic inspection are essential for safe operation. Read and follow all supplied installation instructions and warnings. Purchase and use are subject to our Terms, Conditions & Disclaimer.