Stihl MS 661 Review: The Heavy-Lifting King of Forestry
If you have ever stood at the base of a three-foot-wide white oak with a 20-inch bar and felt like you were bringing a knife to a gunfight, you know why the Stihl MS 661 exists. We have spent decades pulling triggers on everything from top-handle arborist saws to monster milling rigs, and the MS 661 C-M occupies a very specific, very holy place in the lineup. It is the saw you reach for when getting it done is not enough—you need to dominate the timber.
This is not your weekend warrior tool for cleaning up storm debris. If you are looking for something to prune your apple trees, go read our Husqvarna 120 review and save yourself $1,200. The MS 661 is a 91.1cc professional-grade beast.
At a Glance: How the 661 Stacks Up
| Model | Displacement | Power Output | Weight (Powerhead) | Best For |
|---|---|---|---|---|
| Stihl MS 661 C-M | 91.1 cc | 7.2 bhp | 16.3 lbs | Professional felling |
| Stihl MS 462 | 72.2 cc | 6.0 bhp | 13.2 lbs | All-around pro saw |
| Husqvarna 592 XP | 92.7 cc | 7.6 bhp | 16.3 lbs | Extreme bucking |
| Stihl MS 391 | 64.1 cc | 4.4 bhp | 13.7 lbs | Farm and ranch heavy |
Stihl MS 661 Review: What Makes the 661 Roar?
The C-M in the name stands for Comfort and M-Tronic. If you are used to the old Stihl 066 or early MS 660s, the first thing you will notice is the absence of adjustment screws on the carburetor. A microprocessor-controlled ignition system handles everything, monitoring engine temperature, speed, and fuel quality 30 times per second.
When you are buried in a 36-inch piece of frozen hickory, you can feel the torque curve. It is flat and wide. Unlike a Stihl MS 261 which loves to scream at high RPMs, the 661 has a grunt that feels like a diesel truck. You can lean on it.
Honest Downside
It is a workout. If you are not physically fit, this saw will own you by noon. It is a massive investment at $1,200-$1,400. If the M-Tronic solenoid fails, you are going to the dealer, not fixing it with a screwdriver.
Who It Is Best For
Professional fallers, serious firewood producers, and anyone running an Alaskan mill. If you mostly cut wood under 24 inches, look at the Stihl MS 462 or Stihl MS 271 instead.
Chainsaw Safety
At 91.1cc and 7.2 bhp, this saw is a serious piece of machinery. It demands physical fitness, experience, and constant attention. Always use the decompression valve—forgetting it can injure your shoulder.
This is a specialist tool for experienced operators. Read our chainsaw safety guide.
Maintenance and Serviceability
The ElastoStart handle takes the bite out of high-compression pulls. Captive bar nuts are a godsend. The HD2 filter can be washed with soapy water. Side-access tensioning is standard and well-positioned.
For bar and chain specifications, see our stihl-chainsaw-bar-size-guide-match-your-model-to-the-right-bar-chain.
Gas vs Battery
In the 90cc class, battery technology simply does not exist yet. For big timber felling and milling, gas is the only option. The MS 661 represents the pinnacle of what a traditional petrol-powered saw can be. Check our gas vs electric chainsaw guide.
Final Verdict
If you are a professional faller, a serious firewood producer, or someone running an Alaskan mill, the answer is a resounding yes. The MS 661 C-M is the pinnacle of what a traditional petrol-powered saw can be. It combines the raw, visceral power of the old days with the intelligent management of the modern era.
However, if you find yourself mostly cutting wood under 24 inches, do yourself a favor and look at the Stihl MS 462 or Stihl MS 271. The 661 is a specialist.
SAWOFF Rating: 4.8 / 5
Get out there and cut. Safely.
Frequently Asked Questions
What fuel mix should I use for the MS 661?
Always use a 50:1 ratio of high-quality 89 octane gasoline and high-quality 2-cycle engine oil. We recommend Stihl MotoMix or ethanol-free canned fuel. Ethanol is the enemy of the M-Tronic solenoids.
Can I run a 42-inch or 48-inch bar on the 661?
Yes, the 661 has the oiling capacity and torque to pull a 48-inch bar, but switch to a skip-tooth chain to keep RPMs up. For daily use, a 32-inch or 36-inch bar is the sweet spot for balance and performance.
My MS 661 is hard to start when warm. What is wrong?
This often means the M-Tronic system needs a reset or the solenoid valve is getting sticky. Use the decompression valve and try the calibration cut. If the problem persists, the solenoid may need cleaning or replacement.
How does the 661 compare to the Husqvarna 395XP?
The 395XP is an older design with no electronics—just a raw manual carb. Some prefer the 395XP because they can tune it themselves. However, the 661 has much better anti-vibration and is generally more snappy in throttle response.
Is the MS 661 good for a chainsaw mill?
It is one of the most popular saws for milling due to its high displacement. Milling is the hardest work a saw can do. Run it slightly rich and give it plenty of idle time to cool between passes.
What is the difference between the 661 and the 661 Magnum?
In the US, the Magnum branding is often used for marketing. Technically, the modern pro version is the 661 C-M. They are effectively the same high-output professional machine.
How often should I clean the HD2 filter?
If cutting dry, dead wood, check it every day. If felling green timber, you can usually go 3-4 days. The HD2 filter can be washed with warm soapy water and dried.
What is the weight of the MS 661 powerhead?
The MS 661 powerhead weighs 16.3 lbs (7.4 kg). With a 32-inch bar and full fluids, you are looking at around 20+ lbs total.
