Stihl MS 391 Chainsaw

STIHL MS 391: High-Torque Heavyweight for Logging and Agricultural Felling

The STIHL MS 391 is an industrial-duty, high-torque petrol chainsaw engineered to bridge the gap between heavy farm maintenance and full-scale forestry production. Driven by a 64.1 cc 2-MIX engine delivering 3.3 kW (4.5 bhp), it generates massive cutting force across a broad RPM range without the weight penalty of larger pro-saws. Designed to pull 16″ to 20″ guide bars effortlessly through dense timber, hardwood trunks, and thick cordwood, the MS 391 utilizes STIHL’s advanced four-channel stratified scavenging technology to cut fuel consumption by up to $20\%$ while reducing exhaust emissions. Whether you are clearing windblown trees across Kildare farmland or cutting firewood for the season, the MS 391 provides a rugged, high-output power-to-weight ratio ($1.9 \text{ kg/kW}$) built to handle grueling cutting shifts.

Engineering & Performance Highlights

• High-Torque 64.1 cc 2-MIX Engine: Generates 3.3 kW (4.5 bhp) of raw cutting power, maintaining high blade speed under heavy loads when bucking large-diameter logs.

• Pre-Separation Air Filtration System: Utilizes centrifugal force to reject heavy dust and chips before reaching the air filter, extending filter lifespan up to five times longer than conventional saws.

• STIHL Ematic™ Variable Oil Delivery: Features a controllable-delivery oil pump that optimizes lubrication based on bar length and timber condition, reducing bar-chain oil consumption by up to $50\%$ in the ‘E’ position.

• Integrated Decompression Valve: Opens the cylinder during the starting pull to relieve compression resistance, protecting the recoil starter assembly and ensuring smooth cord pulls.

• STIHL Anti-Vibration Spring Buffers: Cell-matrix buffers isolate handle contact points from engine vibration, maintaining low handle oscillation levels ($4.0 \text{ m/s}^2$) to reduce operator wrist fatigue.

• Carburettor Compensator Unit: Automatically adjusts air-to-fuel ratios as the filter dirtying progresses, preserving consistent engine performance and fuel efficiency over extended shifts.

• Tool-Free Bayonet Cap Closures: Heavy-duty, flip-up caps on fuel and oil tanks allow fast, leak-free servicing in the field without searching for tools.

• Lateral Chain Tensioning: The tensioning screw is accessed through the sprocket cover side, keeping hands away from the sharp chain during adjustment.