STIHL engine technology means low fuel consumption, longer run times and reduced emissions in this high-powered chainsaw. The MS 391 features our newest engine technology that adds fuel efficiency while reducing emissions as compared to other models. Though equal in weight, the MS 391 is more powerful than the MS 311. Add to that an optimal power-to-weight ratio and you have a chainsaw that’s cut out for the big jobs in field, farm and ranch. Felling trees, cutting firewood and cleanup after the storm just got a whole lot easier with the rugged MS 391. 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. Pre-Separation Air Filtration System This time-saving technology boosts the efficiency of the engine’s filter system, doubling the time between air filter cleanings. Air drawn into the engine is first separated via centrifugal force, ejecting the heavier dirt particles before being routed to the air filter. This pre-separation means less dirt to be captured by the air filter, resulting in less frequent cleaning and maintenance. 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. IntelliCarb™ Compensating Carburetor The IntelliCarb™ Compensating Carburetor is designed to automatically adjust the air/fuel ratio when the air filter becomes restricted or partially clogged and maintains the engine’s correct RPM. IntelliCarb™ uses air from the clean side of the air filter to control the diaphragm and flow of fuel. As the air filter becomes dirty and less air is available for the carburetor, the IntelliCarb™ system adjusts the fuel flow to compensate for the decrease in air flow. This is in contrast to typical carburetors that utilize this air from the “dirty” side of the air box. 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. Specifications POWER SOURCE Gas POWERHEAD WEIGHT 13.67 lbs. GUIDE BAR LENGTH (Recommended) 20 in. OILOMATIC® CHAIN 3/8" RS3 CHAIN OIL CAPACITY 11.8 oz. ENGINE POWER 4.4 bhp FUEL CAPACITY 20.3 oz. DISPLACEMENT 64.1 cc Note: STIHL recommends #3624 (33 RS3 72) OILOMATIC® saw chain and 20" 3003 008 8921 Ematic™ guide bar combination. Compatible guide bar ranges: 16" to 20"
