STIHL 661 C-M Chainsaw Review


When it comes to professional-grade chainsaws designed for felling large trees and managing substantial milling tasks, the STIHL MS 661 C-M MAGNUM is a name that often surfaces at the top of the list. This powerhouse chainsaw, with its impressive power-to-weight ratio and advanced STIHL M-Tronic™ engine management technology, promises efficiency, durability, and less vibration alongside a 20% increase in fuel efficiency compared to its predecessors. Let’s dive deeper into what makes the MS 661 C-M a standout choice for professionals and discerning users.

STIHL 661 CM Chainsaw on a white background

Key Features

  • Power Source: Gas-powered, ensuring robust performance for the most demanding tasks.
  • Powerhead Weight: At 16.5 lbs., it strikes an excellent balance between power and manageability.
  • Guide Bar Length: Recommended 25 inches, suitable for a wide range of cutting tasks.
  • Engine Power: A formidable 7.2 brake horsepower (bhp), capable of tackling large and tough trees effortlessly.
  • Displacement: 91.1 cc, indicating a powerful engine size for professional-grade work.
  • Fuel and Oil Capacity: With a fuel capacity of 28.7 oz. and an oil capacity of 13.5 oz., it’s designed for extended use without frequent refills.
  • Emission and Technology: Features Reduced-Emission Engine Technology and STIHL M-Tronic™ for optimal performance and environmental care.
  • Comfort and Convenience: Equipped with an ElastoStart™ handle, decompression valve, and adjustable automatic oiler for ease of use.

Performance and Usability

The MS 661 C-M MAGNUM is built for high-demand tasks, evidenced by its powerful engine and large displacement. The inclusion of STIHL’s M-Tronic™ technology automates engine management, ensuring the chainsaw operates optimally under various conditions without the need for manual carburetor adjustments. This technological advantage, combined with the chainsaw’s efficient fuel consumption and emission-reducing capabilities, positions the MS 661 C-M as a top choice for professionals concerned about environmental impact.

STIHL 661 C-M sitting on a cutted log

For usability, STIHL has incorporated several features aimed at improving the user experience. The ElastoStart™ starter handle and decompression valve significantly reduce the effort needed to start the chainsaw, a valuable feature when working long hours. Additionally, the anti-vibration system minimizes fatigue, allowing for more comfortable and extended use.

Practical Considerations

STIHL 661 C-M Chainsaw sitting in the grass beside already cut big trunk

Excel in heavy-duty tasks, such as milling with a chainsaw mill attachment or felling large trees. Its power does not compromise the saw’s handling, thanks to its advanced anti-vibration system and ergonomically designed features. The adjustable automatic oiler and side-access chain tensioner are particularly appreciated for their convenience during long work sessions.

Pros and Cons of the STIHL MS 661 C-M MAGNUM Chainsaw


  • With a 7.2 bhp engine and 91.1 cc displacement, the MS 661 C-M delivers the power needed for felling large trees and handling heavy-duty milling tasks, making it a workhorse for professional users.
  • The inclusion of STIHL’s M-Tronic™ engine management technology ensures optimal engine performance under various conditions by automatically adjusting to changes in environment, fuel quality, and air filter cleanliness.
  • This model offers a 20% increase in fuel efficiency compared to its predecessors, alongside reduced-emission engine technology. This not only makes it more economical to run but also less impactful on the environment.
  • Designed with a magnesium frame and side cover, the MS 661 C-M is built to withstand the rigors of professional use, ensuring longevity and reliability.
  • Features like the ElastoStart™ handle, decompression valve, and anti-vibration system significantly reduce the physical strain on the user, making it more comfortable for extended use.
  • The chainsaw includes an adjustable automatic oiler, side-access chain tensioner for easy maintenance, and a large air filter for extended service intervals. Safety is enhanced with the inclusion of large felling dogs and a chain brake.


  • At 16.5 lbs., the saw is on the heavier side, which could be a factor for some users, especially during long periods of use or for those not used to handling such powerful equipment.
  • Reflecting its professional-grade features and performance, the MS 661 C-M comes with a premium price tag, which may be beyond the budget of non-professional users or those with less intensive needs.
  • The advanced features and sheer power of this chainsaw might be more than what’s necessary for casual or occasional users, making it potentially overwhelming or underutilized in less demanding applications.
  • While the M-Tronic™ system offers significant benefits in terms of automatic engine adjustment, some users might prefer the ability to manually adjust their saw for specific conditions or fear potential electronic malfunctions.
  • Given its size and power, the MS 661 C-M might not be the best choice for smaller, more delicate cutting tasks where a lighter, more maneuverable saw would be preferable.

STIHL MS 500 i vs. STIHL MS 661 C-M

Maintenance of MS 661 C-M MAGNUM

  1. Chain Maintenance involves regular inspection for sharpness since a dull chain can make cutting inefficient and raise the risk of kickback. Equally important is maintaining the correct chain tension; too loose, and it may come off the bar, while too tight can cause excessive wear or even breakage.
  2. Bar Care is crucial for the smooth operation of your chainsaw. Cleaning the groove and oil holes ensures the chain moves smoothly and receives proper lubrication. Rotating the bar regularly helps to promote even wear, extending the life of both the bar and chain.
  3. Air Filter Maintenance ensures that the engine receives clean air, which is vital for maintaining engine performance and fuel efficiency. A clogged air filter should be cleaned or replaced to prevent reduced airflow to the engine.
  4. The Fuel System needs attention to ensure the chainsaw operates effectively. Using fresh fuel with the correct oil mix ratio as specified by STIHL is essential, as is checking the system for leaks and ensuring the fuel filter is clean to prevent blockages.
  5. Spark Plug inspection and maintenance are critical for reliable starting and optimal engine performance. A fouled or worn spark plug should be cleaned or replaced as part of regular maintenance.
  6. Cooling System maintenance involves keeping the cooling fins on the cylinder clean to prevent the engine from overheating, which can lead to significant engine damage.
  7. Lubrication is key to the smooth operation of your chainsaw. Regularly checking and refilling the oil and ensuring the adjustable oiler is correctly set for the current cutting conditions will help maintain the chain’s longevity and performance.


  1. When the Engine Won’t Start, checking the fuel mix, inspecting the spark plug, setting the choke correctly, and ensuring the air filter isn’t clogged are all steps that can help identify and solve the issue.
  2. If the Engine Stalls or Runs Poorly, ensuring there’s proper fuel in the tank, checking the air filter and spark plug, and possibly adjusting the carburetor settings (which might require professional help) are recommended actions.
  3. A Chain that Moves Slowly or Not at All could be due to improper chain tension, an engaged chain brake, low oil levels, or a worn drive sprocket. Addressing these issues can often restore normal operation.
  4. Excessive Vibration may indicate loose components, worn-out anti-vibration mounts, or issues with the chain’s sharpness and tension. Tightening, replacing, or adjusting these components can reduce vibration.
  5. Overheating can be a result of blocked air intake areas, inadequate chain lubrication, or a chain that’s too tight. Cleaning the chainsaw, refilling the oil, and adjusting the chain tension can help alleviate overheating issues.

By adhering to a routine maintenance schedule and promptly addressing any troubleshooting signs, you can ensure your STIHL MS 661 C-M MAGNUM chainsaw remains a reliable and efficient tool for your cutting needs. For more complex issues, especially those related to internal engine components or the M-Tronic system, professional service is recommended.


The STIHL MS 661 C-M MAGNUM chainsaw is an investment in efficiency, reliability, and power for the professional user. Its design reflects an understanding of the needs of those who require a high-performance chainsaw for demanding tasks. With its blend of power, advanced technology, and user-focused features, the MS 661 C-M stands out as a preferred choice for professionals looking to maximize productivity and minimize effort. Whether it’s for felling large quantities of trees or undertaking substantial milling projects, the MS 661 C-M is engineered to deliver performance that professionals can rely on.


  1. Is the STIHL MS 661 C-M suitable for residential backyard use?
    While the MS 661 C-M is primarily designed for professional use due to its power and size, it can be used for residential purposes by experienced users. However, it might be overkill for typical backyard tasks, given its professional-grade capabilities and price point.
  2. Can I use the MS 661 C-M for precision cutting tasks?
    The MS 661 C-M is designed for power and efficiency in felling large trees and milling. While it can perform precision tasks, its size and power make it more suited to heavy-duty work. For more delicate or precise cutting, a lighter and more maneuverable saw might be preferable.
  3. How does the M-Tronic™ system benefit me?
    The M-Tronic™ system provides an intelligent engine management that automatically adjusts the fuel-air mixture, taking into account external conditions such as temperature, altitude, and fuel quality. This ensures optimal performance, easier starts, and better fuel efficiency without the need for manual carburetor adjustments.
  4. What maintenance does the MS 661 C-M require?
    Regular maintenance includes checking and cleaning the air filter, inspecting the chain and bar for wear, sharpening the chain, ensuring the oiler functions correctly, and checking the fuel system for leaks. The advanced design aims to make maintenance straightforward, with features like the toolless fuel and oil caps and easily accessible air filter.
  5. How does the decompression valve work, and when should I use it?
    The decompression valve reduces the pressure in the cylinder, making it easier to pull the starter rope and start the saw. It’s particularly useful when starting the saw cold or after an extended period of non-use. Simply press the valve before starting, and it will automatically close once the engine fires up.
  6. What’s the difference between the MS 661 C-M and the MS 661 R C-M?
    The primary difference is the wrap-handle design of the MS 661 R C-M, which is available in select areas. This design offers an alternative grip for certain types of cuts and might be preferred by professionals who need that extra maneuverability and control.
  7. Can the MS 661 C-M handle long bars for milling large slabs?
    Yes, the MS 661 C-M can accommodate long guide bars, making it suitable for milling large slabs. Its power and adjustable oiler ensure it can drive a long chain effectively for slabbing and other milling tasks.
  8. Is the anti-vibration system effective for long hours of use?
    STIHL’s anti-vibration system significantly reduces the vibrations felt by the operator, minimizing fatigue and making the saw more comfortable to use for extended periods. This feature is particularly appreciated by professionals who use the saw for long hours.
  9. How environmentally friendly is the MS 661 C-M?
    The MS 661 C-M features STIHL’s Reduced-Emission Engine Technology, making it cleaner than EPA and/or CARB exhaust emission standards. This commitment to environmental care ensures the saw produces low exhaust emissions without compromising on power.
  10. Can I adjust the oil flow for different cutting conditions?
    Yes, the adjustable automatic oiler allows you to modify the lubrication of the guide bar and chain based on the length of the bar and the cutting conditions. This feature ensures optimal performance and longevity of the cutting equipment.

Thanks for joining us on this deep dive into the STIHL MS 661 C-M MAGNUM Chainsaw! We’re eager to hear your thoughts and experiences with this powerful tool. Whether you’re a seasoned professional who’s wielded this beast in the field or someone eyeing it for future projects, your insights are invaluable. Drop a comment below to share your stories, tips, or any questions you might have. Don’t forget to share this review with fellow chainsaw enthusiasts and those contemplating their next big purchase. Together, let’s keep the conversation buzzing and the community informed. Happy cutting, everyone!

David Murray
David Murray
Forestry Author

I'm David Murry, a forestry equipment specialist with a focus on chainsaw operation. With over 13 years of experience, I've honed my skills in operating and maintaining a wide range of machinery, from chainsaws to log splitters. My passion for the outdoors and commitment to sustainable forestry drive my work, which emphasizes safety, efficiency, and staying updated with industry advancements. Additionally, I'm dedicated to sharing my expertise and promoting environmental awareness within the forestry community.


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