Master The Stihl MS 250: Complete Step-by-Step Chainsaw Starting & Troubleshooting Guide

Start your Stihl MS 250 chainsaw quickly and safely by engaging the chain brake, depressing the throttle trigger to lock the Master Control Lever down into Full Choke, and pulling the starter rope until the engine briefly fires. Immediately click the lever up one notch to the Half Choke starting throttle position, pull the rope again to start the engine, and then tap the throttle to release the saw into its standard running idle. Following this precise sequence prevents engine flooding and ensures consistent ignition in all weather conditions.

Essential Safety, Fueling, and Pre-Start Checklist for the MS 250

Before attempting to start the Stihl MS 250, you must prepare the machine and yourself. The MS 250 is a high-performance, 45.4cc homeowner and landowner chainsaw that operates at speeds up to 14,000 RPM. Improper starting procedures not only lead to engine flooding and premature starter assembly wear, but they also pose significant physical safety risks.

You must establish a clean, clear starting area free of debris, twigs, or loose soil that could be drawn into the flywheel fan or caught by the cutting chain. Never drop-start a chainsaw; this dangerous technique involves holding the starter rope in one hand and dropping the body of the saw with the other, which can result in severe kickback injuries or loss of control.

• Personal Protective Equipment (PPE): Safety glasses with side shields, hearing protection (minimum 22 dB NRR rating), heavy-duty logging chaps (certified to ASTM F1897), steel-toe boots, and snug-fitting leather work gloves.
• Fuel Requirements: Fresh, unleaded gasoline with a minimum octane rating of 89. Ethanol content must not exceed 10% (E10), as higher levels cause lean running, corrosion, and engine damage.
• Two-Stroke Engine Oil: Premium air-cooled two-stroke engine oil (such as STIHL HP Ultra) mixed at a precise 50:1 ratio (2.6 fl. oz. of oil per 1 gallon of gasoline).
• Chain Lubricant: High-quality bar and chain oil formulated with tackifiers to prevent oil sling. Use winter-grade oil for temperatures below 32°F (0°C) and summer-grade for warmer weather.
• Tension Check: The saw chain must be properly tensioned. When cold, the chain should fit snugly against the underside of the bar guide, but still be easily rotated by a gloved hand.
• Estimated Prep Time: 10 minutes.
• Operating Budget: $15–$30 for basic consumables (fuel, oil, safety glasses).

Step-by-Step Guide to Cold and Warm Starting Your Stihl MS 250

The Stihl MS 250 uses a specialized Master Control Lever that integrates the choke, throttle lock, and ignition switch into a single control mechanism. Understanding how to manipulate this lever is the key to effortless starting.

Step 1: Engage the Chain Brake

Place the chainsaw on a flat, level surface. Push the hand guard (the black plastic paddle in front of the handlebar) forward toward the guide bar until you hear a sharp, distinct click. This engages the chain brake, locking the clutch drum and preventing the cutting chain from spinning during ignition. Squeeze the protective scabbard off the guide bar to expose the chain, ensuring the bar and chain are not contacting the ground, rocks, or any other obstructions.

Warning: Never attempt to start the chainsaw with the chain brake disengaged. If the engine fires at high starting idle, the chain will spin immediately, creating an extreme safety hazard.

Step 2: Set the Master Control Lever to Full Choke (Cold Start)

The Master Control Lever is located on the rear handle's left side. You will notice four positions: Off (0), Run (I), Warm Start ()(), and Cold Start (Full Choke).

Because of an internal safety lockout, you cannot move the lever to the bottom Cold Start position directly. First, depress the throttle trigger lockout lever on top of the handle, squeeze the throttle trigger on the bottom of the handle, and then push the Master Control Lever all the way down into the bottom position (represented by the closed choke flap icon). Release the trigger first, then release the Master Control Lever. This locks the internal carburetor butterfly valve shut and sets the throttle to a high-idle position.

Step 3: Secure the Chainsaw on Flat Ground

Maintain a rigid, stable stance to prevent the saw from moving when you pull the starter rope. Place your right boot toe firmly inside the rear handle's wide bottom opening. Grasp the front handlebar with your left hand, locking your elbow straight. This three-point contact system (right foot, left hand, and ground) secures the machine, preventing the guide bar from tipping or kicking upward.

Pro-Tip: If the ground is wet, muddy, or uneven, you can use the thigh-lock method. Place the rear handle firmly between your knees, grip the front handlebar with your left hand keeping your elbow locked, and hold the starter handle with your right hand. Only use this method if you can maintain absolute control of the machine.

Step 4: Pull the Starter Cord to Prime the Engine

Grasp the starter rope handle with your right hand. Pull the starter rope slowly outward until you feel a firm resistance (this engages the starter pawls inside the flywheel shroud). Once you feel resistance, pull the rope upward with a rapid, continuous, and aggressive motion.

Do not pull the rope to its absolute limit, as this can snap the starter cord or damage the recoil spring. Guide the rope back into the housing slowly; do not let it snap back. Repeat this pulling process (typically 2 to 5 times) until you hear the engine briefly fire, make a coughing or "popping" sound, and then die.

Step 5: Transition the Master Control Lever to Warm Start

The moment the engine "pops," it has drawn enough fuel into the cylinder for ignition. If you continue to pull the cord while the lever is in the bottom Cold Start position, you will flood the engine.

Move the Master Control Lever up one position to the Warm Start/Starting Throttle setting (indicated by the open choke flap icon with lines). You do not need to touch the throttle trigger to perform this movement; simply click the lever upward one notch. This opens the carburetor choke valve while keeping the throttle locked in the high-idle position.

Step 6: Pull the Starter Cord to Run the Engine

With the saw still secured to the ground, pull the starter rope using the same technique: pull slowly to find resistance, then pull upward with a swift, strong stroke. The engine should start running within 1 to 3 pulls.

Because the choke is open but the throttle is locked at high idle, the engine will run at a loud, high RPM. The chain brake is still engaged, which means the clutch is slipping against a locked drum.

Warning: Do not allow the engine to run in the Warm Start/High Idle position with the chain brake engaged for more than 15 seconds. The friction will rapidly overheat the clutch drum, melt the plastic engine housing, and ruin the oil pump assembly.

Step 7: Squeeze the Throttle to Set Normal Idle

Immediately after the engine starts, tap or "blip" the throttle trigger with your right index finger. This action automatically releases the Master Control Lever from the Warm Start position and jumps it up to the normal Run (I) position.

The engine speed will immediately drop down to a quiet, standard idle. The clutch will disengage, and the engine will run freely without spinning the drive sprocket.

Step 8: Disengage the Chain Brake and Begin Operation

Pick up the chainsaw by the front handlebar and rear handle. Pull the hand guard back toward the front handlebar with your left hand until you hear a click. The chain brake is now disengaged, and the cutting chain is free to rotate.

Squeeze the throttle trigger briefly to ensure that the chain spins freely and that the automatic oiler is throwing a light spray of bar oil off the tip of the guide bar onto a clean surface (like a log or stump). Your Stihl MS 250 is now ready for cutting.

Step 9: How to Start a Warm Engine

If you have been cutting and stopped the engine to refuel or clear debris, the cylinder is already warm. To restart a hot engine:

1. Engage the chain brake.
2. Push the Master Control Lever directly down to the Warm Start position ()(), bypassing the Cold Start position. (You will still need to squeeze the throttle trigger to allow the lever to move past the Run setting).
3. Place the saw on the ground and pull the starter cord. It should start on the first or second pull.
4. Blip the throttle immediately to return the saw to standard idle, then disengage the chain brake.

Stihl MS 250 Technical Specifications and Fluid Capacities

Maintaining the structural and operational parameters of your chainsaw is vital for consistent starting. Use the official manufacturer specifications below to calibrate your MS 250.

Diagnosing and Resolving Common Starting Failures on the MS 250

Even with correct starting habits, small mechanical variances or environmental conditions can cause starting issues. Below are the primary failure modes for the Stihl MS 250 and how to resolve them in the field.

Scenario 1: The Engine is Flooded (Excessive Fuel in Cylinder)

• Root Cause: The operator pulled the starter rope too many times while the Master Control Lever was in the Cold Start (Full Choke) position, or failed to switch to the Warm Start position after the initial ignition pop. This fills the combustion chamber with liquid fuel, wetting the spark plug and preventing ignition.
• Actionable Fix: Move the Master Control Lever to the Off (0) position. Use a spark plug wrench (scrench) to remove the top black shroud cover, pull off the boot, and unscrew the spark plug. If the plug tip is wet with fuel, wipe it clean with a dry cloth. Turn the chainsaw completely upside down so the spark plug hole faces the ground. With the Master Control Lever still in the Off position, pull the starter rope rapidly 15 to 20 times to blow excess liquid fuel out of the combustion chamber. Reinstall the dry spark plug, tighten it to 20 Nm (15 ft-lbs), reinstall the boot and cover, and attempt to start the saw in the Run (I) position without using any choke.

Scenario 2: The Starter Cord is Frozen or Extremely Difficult to Pull

• Root Cause: Liquid fuel has filled the cylinder completely, creating a hydrostatic lock (liquids cannot compress, stopping the piston from moving upward). Alternatively, the recoil starter spring has jumped its track, or the starter pawls have broken and wedged inside the flywheel assembly.
• Actionable Fix: Remove the spark plug and pull the starter cord. If the engine spins freely and sprays fuel out of the spark plug hole, the problem was hydro-lock (follow the steps in Scenario 1 to dry the engine). If the cord still resists pulling with the spark plug removed, the issue is mechanical. Unscrew the four sprocket shroud screws, remove the recoil starter assembly, and check the plastic starter rotor, recoil spring, and drive pawls for cracks or misalignment. Clean out any packed sawdust or wood chips, lubricate the spring with light oil, and reinstall the assembly.

Scenario 3: The Saw Starts, but Immediately Dies When Given Throttle

• Root Cause: The fuel filter inside the tank is clogged, restricting fuel delivery under load, or there is air entering the crankcase through cracked fuel lines. This can also happen if the fuel tank vent is blocked, creating a vacuum that prevents fuel from being drawn into the carburetor.
• Actionable Fix: Use a wire hook to pull the fuel pickup body (filter) out of the fuel tank filler neck. Inspect the mesh filter; if it is dark, discolored, or slimy, pull it off the fuel line and press on a new OEM replacement filter. Next, inspect the black rubber fuel line for hairline cracks, especially where it bends to enter the engine housing. If cracks are found, replace the fuel line. Finally, clean the fuel tank vent—located near the rear handle—by spraying it with compressed air to clear away sawdust.

Frequently Asked Questions

Why does my Stihl MS 250 flood so easily during a cold start?

The MS 250 has a highly efficient carburetor that delivers fuel rapidly when the choke is closed. It typically only requires 2 to 4 pulls under full choke to draw sufficient fuel for ignition. If you miss the sound of the initial "pop"—which can be quiet and easy to miss in noisy environments—and pull a fifth or sixth time on full choke, liquid fuel will overwhelm the spark plug electrodes.

How do I know if my chain tension is correct before starting?

To test your chain tension, wear heavy leather gloves and pull the chain downward away from the bottom of the guide bar. The drive links should not slip completely out of the bar groove, and the chain should spring back flat against the bar when released. If the chain sags below the bar, loosen the bar nuts, lift the bar tip upward, turn the tensioning screw clockwise until the chain fits snugly, and retighten the bar nuts.

Can I use premium 40:1 fuel mix in my Stihl MS 250?

You should always use the manufacturer-specified 50:1 fuel mixture. Running a richer 40:1 ratio (which contains more oil and less gasoline) increases carbon buildup on the piston head, clogs the spark arrestor screen in the muffler, and causes the engine to run cooler and less efficiently, which can make cold starting much more difficult.

What should I do if my chainsaw chain spins while the engine is idling?

If the chain spins when the Master Control Lever is in the Run position and the chain brake is off, your engine idle speed is set too high, or your clutch springs are broken. Locate the idle speed adjustment screw (marked "LA" on the right side of the carburetor shroud). Start the saw and turn the LA screw counterclockwise until the chain stops rotating, then check that the engine still idles smoothly without stalling. If the chain continues to spin, take the saw to a technician to replace the clutch springs.

Maintain Peak Chainsaw Performance and Reliability

By using the correct starting sequence and keeping your machine calibrated to factory specifications, you will ensure your Stihl MS 250 starts quickly and cuts with maximum power. Keep your saw running cleanly by regularly cleaning the air filter, replacing the spark plug annually, and utilizing high-quality synthetic lubricants.