MS 661 C-M Petrol Chainsaw
Extremely powerful 5.4kW professional saw
Overview
Very powerful high-performance saw with advanced 2-MIX technology and STIHL M-Tronic (M). This electronic engine management system regulates the ignition timing and the fuel supply and automatically registers the external temperature for optimal engine performance, great acceleration and sustained maximum torque. Extremely robust and durable with low vibration levels. Designed for professional use within forestry and big timber harvesting. Supplied with rollomatic E guide bar, not rollomatic ES light as pictured.
You can find videos showing you how to fill your machine with fuel and oil, fit bars and chains and start your chainsaw here.
Versions
Price-
MS 661 C-M - 71 cm / 28"£1,632.00*
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MS 661 C-M - 90 cm / 36"£1,668.00*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
The version(s) available in each country may differ from the above range and specifications; specific details may be subject to change without notice. Please ask your local STIHL Approved Dealer for further information.
Technical data

Technical data
Technical data | Value |
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Displacement cm³ | 91.1 |
Power output kW/bhp | 5.4/7.3 |
Weight kg 1) | 7.4-7.5 |
Power-to-weight ratio kg/kW | 1.4 |
Weight kg 2) | 9.22 / 10.28 / 10.38 |
Bar length cm | 71-90 |
Bar length " | 28-36 |
CO2 g/kWh | 711 |
STIHL Oilomatic saw chain pitch/type | 3/8" RS |
Sound pressure level dB(A) 3) | 105 |
Sound power level dB(A) 3) | 118 |
Vibration values left/right m/s² 4) | 6.9/5.6 |
STIHL Oilomatic saw chain pitch/type | 3/8 ",3/8" |
Tank volume l | 0.85 |
Speed at maximum power rpm | 9.500 |
Bumper spike | Stahlkralle,Steel claw |
Sprocket - number of teeth | 7.7 Z |
Cylinder | Chrom,Chrome |
Filter material | PET-fabric,PET-Gewebe |
Oil pump | Adjustable,einstellbar |
Filter | HD2 filter,Patronenfilter HD2 |
Sprocket | Chain sprocket,Ring sprocket,Ringkettenrad |
Chain tensioning | Lateral chain tensioning,seitliche Kettenspannung,Side chain tension |
Anti vibration system | Standard AV-System |
Handle type | Standard grip,Standardgriff |
Exhaust | Standard muffler,Standardschalldämpfer |
Filler cap | Tool free filler cap,WTV werkzeugloser Tankverschluss |
Chain pitch | 3/8" |
Carburettor | STIHL M-Tronic |
EPA Certified fuel consumption glh | 0.751 |
EPA Certified fuel consumption l/h | 2.841 |
Oil tank volume cm3 | 400 |
1) Without fuel, without bar and chain
2) Without fuel, with bar and chain
3) K-factor according to DIR 2006/42/EC = 2.5 dB (A)
4) K-factor according to DIR 2006/42/EC = 2m / s ²
The version(s) available in each country may differ from the above range and specifications; specific details may be subject to change without notice. Please ask your local STIHL Approved Dealer for further information.
Features

Standard features
The version(s) available in each country may differ from the above range and specifications; specific details may be subject to change without notice. Please ask your local STIHL Approved Dealer for further information.
Cutting Attachments

Cutting Attachments
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Rollomatic ES Light
Lightweight version of the STIHL Rollomatic ES, made from hard-wearing special steel. The hollow centre is cut out and then welded using a special laser process. This produces an extremely stable hollow body with a flexible outer and substructure. The result is a weight saving of some 30% compared with Rollomatic ES guide bars.
Technical data Value Pitch 3/8 Inch Sprocket pitch 9.32mm/3/8" Groove width 1.6 mm Groove width 1.6mm/.063" Number of teeth 11 Bar connection 3.003 Number of teeth on the sprocket 11 Bar length 50cm/20",63cm/25",71cm/28" Bar type Stern-RollomaticSuper-Light Versions
Price- Rollomatic ES Light, 3/8", 1.6 mm, 71 cm / 28" (MS 500i and MS 661 only) £146.91*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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Rollomatic ES
The STIHL Rollomatic ES (STIHL Ematic Super) is composed of a solid and particuarly rigid bar with a bar nose which can be replaced entirely. It is therefore ideal for most demanding professional tasks and is used chiefly on heavy duty machines for felling and bucking. Elliptically fomed, angled oil holes increase the flow speed of the chain oil, delivering optimal lubrication and even longer service life for the guide bar.
Technical data Value Bar length 50cm/20",63cm/25",75cm/30",90cm/36" Sprocket pitch 9.32mm/3/8" Pitch 3/8 Inch Groove width 1.6 mm Groove width 1.6mm/.063" Number of teeth 11 Bar connection 3.003 Number of teeth on the sprocket 11 Bar type Stern-RollomaticSuper Versions
Price- Rollomatic ES, 3/8", 1.6 mm, 75 cm / 30" (MS 500i and MS 661 only) £149.80*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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Rollomatic ES
The STIHL Rollomatic ES (STIHL Ematic Super) is composed of a solid and particuarly rigid bar with a bar nose which can be replaced entirely. It is therefore ideal for most demanding professional tasks and is used chiefly on heavy duty machines for felling and bucking. Elliptically fomed, angled oil holes increase the flow speed of the chain oil, delivering optimal lubrication and even longer service life for the guide bar.
Technical data Value Bar length 50cm/20",63cm/25",75cm/30",90cm/36" Sprocket pitch 9.32mm/3/8" Pitch 3/8 Inch Groove width 1.6 mm Groove width 1.6mm/.063" Number of teeth 11 Bar connection 3.003 Number of teeth on the sprocket 11 Bar type Stern-RollomaticSuper Versions
Price- Rollomatic ES, 3/8", 1.6 mm, 90 cm / 36"(MS 661 only) £174.41*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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Rapid Super (RS)
High performance saw chain for professional applications with low vibration levels, smooth cutting behaviour, low chatter and extremely high cutting and borning performance.
Technical data Value Pitch 3/8 inch Drive link gauge 1.6 mm Chain pitch 9.32mm/3/8" Drive link thickness 1.6mm/.063" Required File size 5.2mm / 13/64" Versions
Price- Rapid Super (RS) 3/8", 1.6 mm, 91 drive links, 71 cm / 28" (MS 500i and MS 661 only) £57.36*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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Rapid Super (RS)
High performance saw chain for professional applications with low vibration levels, smooth cutting behaviour, low chatter and extremely high cutting and borning performance.
Technical data Value Pitch 3/8 inch Drive link gauge 1.6 mm Chain pitch 9.32mm/3/8" Drive link thickness 1.6mm/.063" Required File size 5.2mm / 13/64" Versions
Price- Rapid Super (RS) 3/8", 1.6 mm, 98 drive links, 75 cm / 30" (MS 500i and MS 661 only) £63.66*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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Rapid Super (RS)
High performance saw chain for professional applications with low vibration levels, smooth cutting behaviour, low chatter and extremely high cutting and borning performance.
Technical data Value Pitch 3/8 inch Drive link gauge 1.6 mm Chain pitch 9.32mm/3/8" Drive link thickness 1.6mm/.063" Required File size 5.2mm / 13/64" Versions
Price- Rapid Super (RS) 3/8", 1.6 mm, 114 drive links, 90 cm / 36" (MS 661 only) £74.58*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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The version(s) available in each country may differ from the above range and specifications; specific details may be subject to change without notice. Please ask your local STIHL Approved Dealer for further information.
Accessories

Accessories
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Service Kit 16
With Service Kit 16 for STIHL petrol chainsaws you can carry out simple maintenance work on your chainsaw yourself. Regular standard maintenance, such as replacing the air and fuel filters and the spark plug, increases the service life of your chainsaw. And because of this, you yourself can help to ensure that machine components and parts are protected from dirt and damage and that the motor of your chainsaw always works reliably and with optimum performance.
Service Kit 16 for MS 661 includes the following components for standard maintenance:
- HD2 air filter
- Spark plug
- Fuel filter
The STIHL HD2 air filter is suitable for all operating conditions and can therefore be used universally. Thanks to its fine pores, it offers a very high filter quality and filters even the finest dirt from the intake air. By replacing the HD2 filter, the chainsaw motor is reliably protected against the ingress of abrasive dust. The performance is retained, the consumption is low and you can continue to start your STIHL chainsaw as easily as usual.
In order to maintain performance, it is also recommended to replace the spark plug regularly. This is the basis for clean combustion in the engine. The fuel filter keeps the fuel free of foreign particles before it gets into the engine. In this way, it protects the engine and ensures an improved longevity. This must also be replaced regularly in order to function reliably.
To replace the air filter and spark plug, it is best to use the practical combination wrench that you received with your STIHL chainsaw. A cardboard hook is integrated in the packaging of the service kit itself. This allows you to easily remove and replace the fuel filter. You do not need any additional tools.
Technical data Value Suitable for 1) MS 661 1) This service kit can only be used with the following machines
Versions
Price- Service Kit 16 £23.11*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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MotoMix
STIHL MotoMix is our patented premixed fuel, specially blended for ultimate performance.
This 50:1 ready-mixed fuel is a combination of premium non-ethanol, high-octane motor fuel for all STIHL 2-stroke engines which gives you optimum performance, excellent cold start properties, maximum acceleration over the entire rpm range and perfect running characteristics even with a sudden rev change.
MotoMix uses STIHL HP ultra-premium oil for exceptional engine lubrication and extreme cleanliness. It’s fully synthetic and biodegradable for optimal performance and long service life. MotoMix is user- and engine-friendly thanks to fewer emissions (free from ethanol; almost no olefins and aromatic compounds).
Can be kept in storage for up to five years.
Did you know:
- For MotoMix drums (55 l & 200 l), speak with your nearest STIHL Approved Dealer about direct delivery of the fuel to your preferred address. Find out more about our MotoMix promotion here.
Patent EP 2031043
Technical data Value Octane number >95 RON Octane rating 93 MOZ Benzene content 0.03 % Vol. Sulphur content 3 mg/kg Shelf life up to 5 Years Density at 15°C 690 kg/m3 Olefin content 0.1 % Vol. Vapour pressure at 40 °C 61 kPA Two-stroke oil content 1.8 % Vol. Versions
Price- MotoMix 5 l £25.00*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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ForestPlus chain oil
Based on high-quality mineral oils, ForestPlus is suitable for use with all chainsaws, including harvesters. ForestPlus delivers reliable chain lubrication and no resin build up, even during prolonged down times.
Versions
Price- ForestPlus chain oil - 5 l £26.54*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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HP Ultra 2-stroke engine oil
Fully synthetic oil with exceptional lubrication properties. Burns with extremely low residue due to ash-free additive. Suitable for continuous use under the most demanding engine conditions. Performance class: JASO-FB, ISO-L-EGB. Fuel/oil ratio 50:1. Recommended for STIHL 4-MIX engines.
Versions
Price- HP Ultra 2-stroke oil - 1 l (for 50 l) metering bottle £30.39*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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Varioclean
Water based, alkaline detergent specifically for dissolving and removing burnt-in resin and oil residue from your machine, and cleaning your tool’s housing, HD2 filter, wire mesh filter or PA filter. The detergent is biodegradable. Avoid contact with the eyes and keep out of reach of children.
To use Varioclean, first wait for your machine to cool down. Then, spray it onto the surface of the part you are cleaning and leave it for a maximum of 5 minutes, so the cleaner is not allowed to dry. Then, wash it off with water and wipe with a cloth to dry. We recommend you wear safety glasses when doing this.
Technical data Value Shelf life 3 Years Biodegradable Yes Versions
Price- Varioclean - 500ml £11.23*
* Manufacturer's recommended retail price updated as of May 2022. The manufacturer's recommended retail prices are subject to change without notice.
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The version(s) available in each country may differ from the above range and specifications; specific details may be subject to change without notice. Please ask your local STIHL Approved Dealer for further information.
Documents
Owners manuals and safety brochures
Languages | Date | Link |
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14/07/2022 |