Stihl MS 251 Instruction Manual

Pages 136

Year 2020

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of 136

Stihl MS 251 Specification

The Stihl MS 251 is a mid-range chainsaw designed for homeowners and property managers who need a reliable tool for cutting firewood, felling small trees, and maintaining landscapes. It is equipped with a 45.6 cc, 2-stroke engine that delivers a power output of approximately 3.0 horsepower, providing a robust performance for its class. The saw features a 16 to 18-inch guide bar, allowing versatility in handling various cutting tasks, while the lightweight design, weighing around 10.8 pounds (without fuel and cutting equipment), ensures ease of maneuverability and reduced user fatigue during extended use.

The MS 251 incorporates Stihl’s advanced anti-vibration system, which minimizes vibrations transmitted to the user's hands, enhancing comfort and control. It also includes a pre-separation air filtration system that extends the life of the air filter and reduces maintenance intervals. The side-access chain tensioner simplifies chain adjustments, making it convenient for operators to maintain optimal chain tension with minimal downtime.

Fuel efficiency is improved through the incorporation of Stihl’s fuel-saving technologies, enabling longer run times with a 13.2-ounce fuel tank. The chainsaw also features an Ematic lubrication system with an adjustable oil pump, ensuring precise lubrication of the chain and bar while reducing oil consumption. Safety is addressed with a quick-stop chain brake that halts chain motion in emergencies.

Overall, the Stihl MS 251 combines power, efficiency, and ergonomic design, making it ideal for users seeking a reliable and versatile chainsaw for moderate cutting tasks. It stands out for its durability, ease of use, and reduced environmental impact, aligning with Stihl's reputation for high-quality outdoor power equipment.

Stihl MS 251 F.A.Q.

How do I start a Stihl MS 251 chainsaw?

To start the Stihl MS 251, first ensure the chain brake is engaged. Set the master control lever to the choke position. Pull the starter handle until the engine fires briefly. Move the control lever to the half-throttle position, and pull the starter handle again until the engine starts. Once running, squeeze the throttle trigger to set the engine to idle.

What is the correct way to adjust the chain tension on the MS 251?

To adjust the chain tension, first turn off the chainsaw and ensure the chain brake is engaged. Loosen the nuts on the guide bar slightly. Use a screwdriver to turn the tensioning screw until the chain sits snugly against the underside of the guide bar, but can still be pulled around by hand. Tighten the nuts securely.

What type of fuel mix should I use for the Stihl MS 251?

The Stihl MS 251 requires a fuel mixture of 50:1, gasoline to Stihl two-stroke engine oil. Use fresh, unleaded gasoline with a minimum octane rating of 89, and mix it with high-quality two-stroke oil designed for air-cooled engines.

How often should I clean the air filter on my MS 251?

Clean the air filter on your MS 251 after every 10 hours of operation, or more frequently if working in very dusty conditions. Remove the filter cover, take out the filter, and clean it with warm, soapy water. Allow it to dry completely before reinstalling.

Why won't my Stihl MS 251 start?

If your MS 251 won't start, check for proper fuel mixture, ensure the spark plug is clean and working, and verify that the air filter is not clogged. Also, make sure that the choke is being used correctly and the master control lever is set properly.

How do I sharpen the chain on my MS 251?

To sharpen the chain, use a round file and a file guide that matches the chain’s pitch. Position the file in the guide at the correct angle (usually 30 degrees) and file each cutter with a few strokes until sharp. Ensure all cutters are filed to the same length.

What maintenance should I perform on the MS 251 after each use?

After each use, clean the chainsaw thoroughly, inspect the chain tension, check for any loose nuts or bolts, and ensure the chain is properly lubricated. Also, inspect the guide bar for any wear or damage.

How can I resolve excessive vibration while using the MS 251?

Excessive vibration can be caused by a loose or dull chain, worn guide bar, or improper chain tension. Inspect these components and make the necessary adjustments or replacements. Also, ensure that the anti-vibration mounts are intact and not worn out.

What should I do if the chain oiler is not working?

If the chain oiler is not working, check for blockages in the oil outlet and clean the oil passages. Ensure the oil tank is filled with the correct bar and chain oil. If the problem persists, the oil pump may need servicing or replacement.

How can I prevent my MS 251 from overheating?

To prevent overheating, regularly clean the cooling fins and air intake areas to ensure proper airflow. Use the correct fuel mixture and avoid running the chainsaw at full throttle for extended periods without breaks.