MS 661 C-M

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A professional chainsaw with enhanced fuel efficiency and STIHL M-Tronic™ technology.

Product Description

When professionals need to fell large trees, in large quantities, they reach for the saw they know has the power to get the job done – the MS 661 C-M. Featuring an impressive power-to-weight ratio and STIHL M-Tronic™ engine management technology, the MS 661 C-M chainsaw also delivers less vibration and 20% greater fuel efficiency than the MS 660. Other features include a long-life filter system using HD-2 filter elements to provide longer run times between maintenance, an ElastoStart™ handle, and a high output adjustable oiler. Wrap-handle version available in select areas. See MS 661 R C-M.

Model Features

  • Reduced-Emission Engine Technology - Caring for Nature
    The STIHL Inc. “Caring for Nature” seal identifies its powered products that are more environmentally conscious, producing zero or low exhaust emissions. STIHL Inc. defines “low exhaust emissions” as being cleaner than EPA and/or CARB exhaust emission standards.

    More information

  • STIHL M-Tronic™ 
    This product features M-Tronic™ (M) - a new generation of Intelligent Engine Management that eliminates the low and high speed carburetor adjustment screws, compensates for dirty air filter and changes in elevation and fuel quality for optimum engine power at all times.

    See it in action!

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  • Anti-Vibration System
    STIHL has developed a system for minimizing the vibration levels of handheld outdoor power equipment. The STIHL anti-vibration system helps reduce operator fatigue and provides a more comfortable working experience.
  • STIHL ElastoStart™
    The ElastoStart™ starter handle is an exclusive feature of STIHL. It is a starting grip with a built-in shock absorber that helps reduce the effort when pulling on the starter cord. The ElastoStart™ starter grip noticeably reduces the sudden peak forces (compression) normally felt during cranking. The forces which occur at the grip after the first compression stroke are smoothed out.
  • Decompression Valve
    The decompression valve, also referred to as 'deco' or 'deco valve', vents compression in the cylinder for easier starting. The decompression valve temporarily reduces the compression in the combustion chamber during cranking and helps reduce the effort needed to pull the starter rope. It is opened manually and closes automatically as soon as the engine fires.
  • Side-Access Chain Tensioner
    The side-access chain tensioner makes it much more convenient for the user to adjust the saw chain with a bar wrench as opposed to the typical location of the guide bar adjustment screw.
  • Adjustable Automatic Oiler
    The Adjustable Automatic Oiler allows the user to adjust the lubricant of the guide bar and saw chain for different bar lengths and cutting conditions.


91.1 cc (5.56 cu. in.)
5.4 kW (7.2 bhp)
Flush-Cut: 7.4kg (16.3 lbs.)
Wrap-Handle: 7.66 kg (16.8 lbs.)
825 cc (27.9 oz.)
360 cc (12.2 oz.)
33 RS3
GUIDE BAR LENGTHS (Recommended ranges)
40 to 80 cm (16" to 32")
STIHL recommends #3624 (33 RS3 84) OILOMATIC® saw chain and 25" 3003 000 4030 Ematic™ guide bar combination. The actual listed guide bar length can vary from the effective cutting length based on which powerhead it is installed on.

Important Information

WARNING! The occurrence called “kickback” can cause serious or fatal injury. Always read the instruction manual carefully before using your saw. STIHL uses a green and yellow color-coding system to help you select a powerhead, bar and chain combination that complies with the kickback requirements of ANSI Standard B175.1 (gasoline-powered saws) and §30 of UL 1662/ ANSI Standard B175.1 (electric chainsaws). Ask your STIHL dealer about safe operating procedures and the advantages of the STIHL Quickstop® chain brake, STIHL Quickstop® Plus (Q) additional chain braking feature, STIHL reduced kickback bars and STIHL low-kickback saw chains.

STIHL recommends the use of green reduced kickback bars and green low kickback chains on all STIHL chainsaws.

* The actual listed guide bar length can vary from the effective cutting length based on which powerhead it is installed on.

Note: STIHL recommends use of fuel with no more than 10% Ethanol content. Using fuel with greater than 10% Ethanol content may cause damage to your equipment and may void your STIHL warranty. Learn More…

WARNING! Improper use of any power tool may cause serious or fatal injury. Read, understand and follow carefully the operating and safety instructions in your instruction manual before using such products.

STIHL products sold through U.S. STIHL Dealers are for distribution in the United States only.


MS 661 C-M is rated 4.5 out of 5 by 92.
Rated 3 out of 5 by from Good, but not great - Stihl could do better Now going from the 290 Farm Boss to my 660 Magnum was better than getting the bike of my dreams at six years old! The initial power makes you think no tree is safe near this saw. The power is very good (at least initially) and the weight seems appropriate for the power you get. Unfortunately, I have been much happier with my non-professional 290 that is twice as old as my professional level 660. The 660 drinks gas like a parched desert, and it breaks something far too often. About three years later, the power is not at all what it was its first year. The chain tensioner slider breaks at least annually. I have had to replace the chain sprocket twice. I run it with a 25" bar about 90% of the time and it does well. The other 10% of the time is with a 36" bar which it does not like very much. Thankfully, I kept my old Farm Boss which has saved me several times when the 660 breaks down. I might purchase it again though due to the power to weight ratio, but I may move up to the 880 next time.
Date published: 2019-11-10
Rated 5 out of 5 by from Great Saw Great Saw lot's of Power. Probably heavy for the average guy, but worth it for the amount of power.
Date published: 2019-08-29
Rated 5 out of 5 by from I am completely satisfied with my MS 661C-M I purchased the 661C-M to cut up a couple of mature Tulip Poplars. The saw never came close to bogging down with a 36" bar and a RS yellow chain. It is very easy to start whether cold or hot. I read all the reviews on the Stihl website before buying and noted that some owners complained about difficulty starting the 661 after it is hot. My guess is that they are using the cold start procedure on a hot saw. After the saw is warmed up, you don't need the choke or the decompression valve. Mine almost always starts on the first pull.
Date published: 2019-07-24
Rated 5 out of 5 by from Power house Fires up one pull. Runs great. Pulls a 32 no problem. Was hesitant of buying a m tronic saw but have zero complaints.
Date published: 2019-06-09
Rated 5 out of 5 by from Best saw I’ve ever ran Best saw ive ever ran or owned very dependable I have found anything that will stop it
Date published: 2019-05-14
Rated 5 out of 5 by from Exceptional Chainsaw You get what you pay for with a Stihl. The Stihl MS 661 is no exception. Astounding power and unsurpassed quality and durability make up the MS 661. Amazing precision and thought went into every detail of this uncompromising beast. Crank it, rev it and hold on for the ride of your life. This saw does not disappoint. I love the new starting system. I love the way the master control lever automatically returns to the run position from the stop position. I love that I can access the air filter in literally one second. I love the decompression valve because I don't quite have the gumption I use to have. I love that I have yet to bog this beast down. I love that this saw is ready to work when I am, and doesn't quit until I do. I love that I don't have to worry if this saw is saw enough to saw what I need to saw. I've used this on our disaster relief team jobs as well as other jobs and it has power to spare, even when the 36" bar is completely buried in the cut. No disappointments on this saw at all. Totally impressed. This is true Stihl at its very best. This saw is why Stihl is #1. I've run a 25" and 36" bar on it and both performed exceptionally. I cannot say enough good about this saw. Baby doll's gonna be heavy, at least for me as a 6' 2", 195 lb., 48 yr old beast of burden, with a 36" bar, but not bad with a 25" bar. When you need that power and performance for the large trees, this is the saw you want to have. No compromise, just amazing, raw, unrelenting power. I've always said, if I had to go into the woods for a month and could only take one saw, it would have to be a Stihl. Stihl chainsaws are reliable, durable, dependable. If you've ever had the pleasure of taking one apart, you know their design is nothing short of poetic. If you're debating, debate no more. GET THE STIHL!!!
Date published: 2019-04-14
Rated 4 out of 5 by from Not interchangeable amongst bars I know that Stihl needs to keep the money with Stihl but good grief. I bought the saw to be my milling machine. I went to buy a bar that’s bigger than 50”, but that was a no no! So if you buy the 661 and wanting to put a bigger bar that’s over 50” think again my friend because it won’t happen. Very disappointed in this aspect of the saw.
Date published: 2019-03-26
Rated 5 out of 5 by from Great saw I bought this saw for cutting large trees and to use with a saw mill. I chose Stihl because of the quality and I needed a big horsepower saw. There is no shortage of power and this saw gives me the option to add longer bars (it came with a 25” bar).
Date published: 2019-03-20
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Standard Features

  • Common Features for Chainsaws
    View the features common to many STIHL chainsaws.

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