STIHL MS 661 C-M Professional Gas Chainsaw (91.1cc) - 20"

The STIHL MS 661 C-M is a full-size professional gas chainsaw built for loggers, forestry crews, and heavy tree-removal contractors who need serious cutting power day after day. Paired with a 20" bar, its 91.1cc engine is sized for felling, bucking, and processing large-diameter timber in demanding conditions.

Engineered for maximum cutting power

A high-output 5.4 kW (7.2 hp) engine and STIHL's 2-MIX technology combine to deliver strong, consistent power with lower fuel consumption than older two-stroke designs, so the saw keeps cutting through thick hardwood without bogging down.

Comfort through long working days

A multi-point anti-vibration system with buffer and spring elements isolates the handles from engine vibration, while a heated carburetor keeps the saw running smoothly when temperatures drop, making it practical for cold-weather forestry work.

Less time servicing, more time cutting

Side-mounted chain tensioning and tool-free fuel and oil caps speed up routine adjustments in the field, and a controlled-delivery oil pump can cut bar oil consumption by up to 50% compared to older systems, stretching time between refills.

Key features

• 91.1cc STIHL 2-MIX professional engine, 5.4 kW (7.2 hp)
• 20" guide bar with 3/8" pitch, .050" gauge saw chain
• Heated carburetor for cold-weather starting and running
• Anti-vibration system with buffer and spring elements
• Side-mounted, tool-free chain tensioning
• Controlled-delivery oil pump reduces bar oil use by up to 50%

Specifications

Frequently asked questions

What fuel does the MS 661 C-M run on?

It runs on a 50:1 mix of unleaded gasoline (minimum 89 octane, no more than 10% ethanol) and STIHL two-stroke engine oil; never run it on straight gasoline.

What guide bar and chain come with the saw?

It ships set up with a 20" guide bar and a 3/8" pitch, .050" gauge STIHL saw chain, ready to fuel, mix oil, and cut.

Is the MS 661 C-M a good choice for occasional homeowner use?

Not really — its size, weight, and power are intended for professional forestry and logging work; homeowners cutting firewood occasionally will be better served by a lighter farm or ranch saw.

What is in the box

Each MS 661 C-M ships with the powerhead, a 20" guide bar, a 3/8" pitch saw chain, a bar scabbard, the onboard tool kit, and the owner's manual. Fuel and bar oil are not included and must be supplied separately.