Undaunted MFG 661 Muffler Cover

Enhance power and improve engine cooling with this precision-engineered exhaust system designed for the STIHL MS 661. Made from lightweight 6061 T6 billet aluminum, a high-strength aerospace alloy known for excellent heat dissipation, the one-piece muffler cover optimizes exhaust flow while helping to keep your engine cooler and extend component life.

Proudly manufactured in the USA and backed by a lifetime warranty, this exhaust system delivers lasting durability under demanding conditions.

Compatible Models:
STIHL MS 661

Includes:

• One-piece muffler cover CNC machined from 6061 T6 billet aluminum
• Spark arrestor screen with aperture size compliant with USFS specifications
• High-Temperature Gasket – Made in the USA
• Longer stainless steel top screws with vibration-resistant Belleville washers

Dyno Proven Performance
Tested on a completely stock saw with no modifications other than the muffler 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:

• Apply thread locker on all mounting screws for secure, vibration-resistant assembly
• Post-installation tuning or recalibration is required for optimal performance