The STIHL MS 250 is a legendary entry-level chainsaw that has introduced countless homeowners and professionals to the world of portable power tools. Renowned for its durability, ease of use, and robust performance, this tool has become a staple for managing firewood, clearing storm debris, and tending to backyard trees. However, like any mechanical device that endures demanding conditions, users will inevitably encounter specific operational issues that require attention.
Understanding the Core Mechanics
Before diving into troubleshooting, it is essential to understand the foundational elements that make the MS 250 reliable. This model operates on a two-stroke engine, which requires a precise mixture of gasoline and STIHL HP Ultra two-stroke oil. The chain brake, a critical safety feature, is designed to stop the chain instantaneously in the event of kickback. Additionally, the side-access chain tensioner allows for quick adjustments to maintain optimal cutting efficiency without the need for specialized tools.
Common Starting and Running Issues
Perhaps the most frequent complaint among users revolves around the difficulty in starting the engine or maintaining a steady run. These issues are rarely indicative of a manufacturing defect and are usually the result of environmental factors or routine maintenance oversights. Cold weather, stale fuel, and improper priming are the usual suspects when the pull cord feels stiff or the engine fails to fire up.
Fuel and Freshness
Over time, gasoline degrades, forming a varnish that can clog the delicate ports and filters within the engine. If the saw sits unused for weeks, the ethanol in the fuel may separate and settle at the bottom, causing a lean condition that prevents combustion. Ensuring a fresh mixture of properly mixed fuel is the first step in resolving lethargic performance.
Air Filter Maintenance
A clogged air filter restricts the oxygen necessary for efficient combustion, leading to a loss of power and excessive smoke. Users should inspect the foam filter regularly; if it appears dirty or saturated, it should be cleaned with fresh gasoline, squeezed out gently, and lightly oiled before reinstallation. Neglecting this component forces the engine to work harder, significantly reducing its lifespan.
Chain and Bar Functionality
The cutting efficiency of the MS 250 is entirely dependent on the condition and installation of the chain and bar. A sharp chain reduces user fatigue and prevents the saw from barbing, a dangerous condition where the chain rolls over the wood without cutting. Proper lubrication is equally vital, as a dry chain will overheat and wear prematurely.
Addressing Bar and Chain Noise
Loud rattling or squealing during operation is often misdiagnosed as a mechanical failure of the engine. In most cases, the noise originates from the bar mount nuts vibrating loose or the chain stretching with use. Regularly checking the chain tension—ideally when the engine is cold—is a simple procedure that ensures the chain does not derail during operation.
Chain Tension Adjustment Even with correct initial setup, the chain will loosen as the bar and chain break in. A loose chain can derail and pose a safety hazard. The STIHL side-access tensioner allows for quick fixes without removing the saw from the bar. Users should ensure the chain moves freely along the bottom of the bar but is not so loose that it sags. Dealing with Vibration and Kickback Excessive vibration can lead to user fatigue and long-term joint damage. If the MS 250 begins to vibrate more than usual, the issue is usually related to the balance of the saw. A misaligned clutch drum or a damaged drive sprocket can cause significant shaking that travels up the handles. Kickback Precautions
Even with correct initial setup, the chain will loosen as the bar and chain break in. A loose chain can derail and pose a safety hazard. The STIHL side-access tensioner allows for quick fixes without removing the saw from the bar. Users should ensure the chain moves freely along the bottom of the bar but is not so loose that it sags.
Dealing with Vibration and Kickback
Excessive vibration can lead to user fatigue and long-term joint damage. If the MS 250 begins to vibrate more than usual, the issue is usually related to the balance of the saw. A misaligned clutch drum or a damaged drive sprocket can cause significant shaking that travels up the handles.
