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Stihl MS 661 C-M Chainsaw


Stihl MS 661 C-M Chainsaw

With M-Tronic Engine Management

Professional petrol chainsaw 63cm/25'' bar

Simply the most popular commercial chain saw in the world for felling, trimming and all commercial and forestry applications. The MS 661 C-M is a rugged all-rounder equipped with STIHL's environmentally friendly 2-MIX engine technology for less fuel consumption, less emissions and outstanding cutting performance. In addition the MS 661 C-M features a heavy duty (HD2) air filter system with a radial seal which keeps out fine dust particles combined with the compensator the MS 661 C-M can now be used for 20% longer than the MS 660 before a filter clean is required.

The MS 661 C-M is fitted with STIHL's M-TRONIC electronic engine management system which enables the saw to automatically adjust to varying fuel grades, changes in altitude and temperature and as there are no manual carburettor adjustments starting this saw is easier than ever before, simply push the start level to the on position and pull.

The MS 661 C-M is now the only choice for professionals.

STIHL M-Tronic (M)

This fully electronic engine management system adjusts ignition timing and fuel metering in all operating modes. It also takes external conditions such as temperature, altitude and fuel quality into account. It ensures consistent engine performance, a constant maximum speed and superb acceleration. M-Tronic makes manual carburettor adjustments unnecessary.

Thanks to electronic cold/warm start recognition, now there is only one start position on the combi-lever. The engine starts after fewer pulls and with no change of position, and can immediately accelerate up to speed - even after a cold start. M-Tronic also remembers the settings from the last time the tool was used. So when external conditions are the same, optimal engine performance is available every time you start up again.

Long-life air filter system with HD2 filter

The new professional Stihl chainsaws will win you over with a filter life that is five times longer. They are equipped with a long-life air filter system that removes coarse dirt particles by pre-separation. The new HD2 filter made from polyethylene filter material filters out the finest dust particles and is easy to clean. The PET-covered round filter cartridge can be replaced quickly and without tools. The radial seal minimises the amount of dirt in the carburettor - similar to illustration.

STIHL anti-vibration system

Intense vibration at the handles of power tools can lead to longer-term effects of blood vessels in the hands and arms. STIHL have therefore developed an effective anti-vibration system where by the oscillations from the machines engine are dampened which significantly reduces vibrations at the handles.


This controller in the carburettor prevents the fuel-air mixture getting richer as the air filter becomes clogged - this keeps the fuel/air ratio in the combustion mixture constant and hence also the engine power. The filter doesn't need to be cleaned until an appreciable drop in power occurs.

Controlled-delivery oil pump

The exact chain oil output can be adjusted manually for varying conditions, allowing for a reduction of up to 50%.

Decompression valve

The decompression valve is part of the easy start-system. The valve should be pressed before starting in order to reduce the compression pressure when starting, as well as the effort needed to pull the starter rope. The decompression valve is semi-automatic, meaning that it must be pressed manually before starting, but then closes automatically.

STIHL 2-MIX engine

The two-stroke engine with STIHL 2-MIX technology saves up to 20 % of fuel and reduces emissions by up to 70 % compared to STIHL 2-stroke engines of the same performance class without 2-MIX technology.


This air filter keeps even the finest dust away from the engine, ensuring a particularly long service life. Thanks to special material, the filter can be washed clean, for example with STIHL Variocleanand warm water.


Displacement :
91.1 cc
Power Output:
5.4 kW - 7.3 BHP
7.5 kg - without fuel, bar & chain
STIHL Oilomatic Saw Chain Pitch/type:
Saw Chain Pitch:
3/8 inch
Bar Length:
63 cm - 25 inch

Stihl Chainsaws & Pole Pruners (Stihl-chainsaws-polsaws.pdf, 2,629 Kb) [Download]