Stihl MS 250 Starting Procedure: Pro Tips (7 Troubleshoot Hacks)

Have you ever yanked the starter cord on your Stihl MS 250 until your arm felt like it was going to fall off, only to be met with…nothing? Just an engine that stubbornly refuses to roar to life? I’ve been there, more times than I care to admit. It’s frustrating, especially when you’ve got a pile of logs waiting to be turned into firewood. Over the years, I’ve learned a thing or two about coaxing a reluctant MS 250 into action. This guide is born from those experiences – the successes, the failures, and everything in between. I’m going to walk you through the starting procedure, share some pro tips, and even arm you with a few troubleshooting hacks to conquer those stubborn starts. Let’s get this saw running!

Stihl MS 250 Starting Procedure: Pro Tips (7 Troubleshoot Hacks)

The Stihl MS 250 is a workhorse. It’s reliable, powerful enough for most homeowner tasks, and relatively easy to maintain. Understanding the proper procedure and knowing how to diagnose common issues is crucial.

Understanding Your Stihl MS 250: A Quick Overview

Before diving into the starting procedure, it’s important to understand the key components of your MS 250 that are involved in the process.

• Fuel Tank: Holds the gasoline and oil mixture (usually a 50:1 ratio).
• Air Filter: Prevents debris from entering the engine.
• Carburetor: Mixes air and fuel to create a combustible mixture.
• Spark Plug: Ignites the air-fuel mixture.
• Ignition System: Provides the spark to the spark plug.
• Primer Bulb: Priming the carburetor ensures a more ready fuel supply.
• Choke: Restricts airflow to richen the fuel mixture for cold starts.
• Starter Cord: Used to manually crank the engine.
• Muffler: Reduces engine noise.

Knowing these components will help you understand the starting process and troubleshoot any problems you might encounter.

The Standard Starting Procedure: Step-by-Step

This is the procedure recommended by Stihl. Following it closely will significantly increase your chances of a successful start.

Step 1: Safety First

• Personal Protective Equipment (PPE): Always wear safety glasses, hearing protection, and gloves. I can’t stress this enough. A chainsaw is a powerful tool, and safety should always be your top priority.
• Clear the Area: Ensure there are no obstructions around the saw. You need a safe, stable surface to work on.
• Chain Brake: Engage the chain brake. This prevents the chain from moving during starting, greatly improving safety.

Step 2: Cold Start Procedure

This procedure is for when the saw is completely cold, like after sitting overnight or for several days.

• Activate the Choke: Pull the choke lever all the way out. This restricts airflow, creating a richer fuel mixture needed for cold starts. On the MS 250, this is usually a single lever that you pull out fully.
• Prime the Carburetor: Press the primer bulb several times (usually 5-6 pumps) until you see fuel flowing through the clear fuel line. This ensures that fuel is reaching the carburetor. Don’t over-prime, as this can flood the engine.
• Starting Position: Place the saw on the ground, holding it firmly with your left hand (if you’re right-handed) and placing your foot through the rear handle. Make sure the chain is clear of any objects.
• Pull the Starter Cord: Grip the starter handle firmly and pull the cord sharply and smoothly. Don’t pull it all the way out; about two-thirds of the way is sufficient. Continue pulling until the engine “pops” or sputters briefly. This usually happens after a few pulls.
• Disengage the Choke (Half Choke): Once the engine pops, push the choke lever in one notch. This is the half-choke position.
• Pull the Starter Cord Again: Continue pulling the starter cord until the engine starts and runs smoothly.
• Warm-Up: Allow the engine to warm up for a few seconds before disengaging the chain brake.

Step 3: Warm Start Procedure

This procedure is for when the saw has been running recently and is still warm.

• No Choke: Do not engage the choke.
• Prime (Maybe): If the saw has been sitting for a short period (e.g., 15-20 minutes), you might need to prime the carburetor once or twice. If it’s been less than 5 minutes, priming is usually unnecessary.
• Starting Position: Same as the cold start procedure.
• Pull the Starter Cord: Pull the starter cord until the engine starts.

Step 4: After Starting

• Disengage Chain Brake: Once the engine is running smoothly, disengage the chain brake.
• Idle: Let the saw idle for a few moments to allow the engine to warm up fully.
• Test the Throttle: Gently squeeze the throttle to ensure the engine responds smoothly and the chain spins freely.

Pro Tips for Easier Starting

These are tricks I’ve learned over the years that can make starting your MS 250 easier and more reliable.

Tip 1: Fresh Fuel is Key

• The Problem: Gasoline degrades over time, especially when mixed with oil. Old fuel can clog the carburetor and make starting difficult.
• The Solution: Always use fresh fuel, ideally less than 30 days old. I always write the date I mixed the fuel on the can with a permanent marker.
• Stabilizer: Use a fuel stabilizer, especially if you don’t use your saw frequently. This helps prevent fuel degradation. I recommend a product like Stihl Fuel Stabilizer or STA-BIL. Add it to your fuel mixture according to the manufacturer’s instructions.
• Ethanol-Free Fuel: If possible, use ethanol-free gasoline. Ethanol can attract moisture, which can lead to fuel system problems. Ethanol free fuel is especially beneficial in older machines.

Tip 2: The Importance of a Clean Air Filter

• The Problem: A dirty air filter restricts airflow, which can affect the air-fuel mixture and make starting difficult.
• The Solution: Regularly clean your air filter. I recommend cleaning it after every 5-10 hours of use, or more frequently if you’re working in dusty conditions.
• Cleaning Procedure: Remove the air filter cover and the filter itself. Tap the filter gently to remove loose debris. You can also use compressed air to blow out the dirt from the inside out. For a more thorough cleaning, wash the filter with warm, soapy water. Rinse it thoroughly and allow it to dry completely before reinstalling.
• Filter Type: The MS 250 typically uses a felt or nylon mesh air filter. Replace the filter if it’s damaged or excessively dirty.

Tip 3: Spark Plug Maintenance

• The Problem: A fouled or worn spark plug can prevent the engine from starting.
• The Solution: Inspect the spark plug regularly. I recommend checking it every 25 hours of use.
• Inspection: Remove the spark plug and examine it. Look for signs of fouling (carbon buildup), cracking, or damage. The electrode should be clean and have a sharp edge.
• Cleaning: If the spark plug is fouled, you can clean it with a wire brush. Be careful not to damage the electrode.
• Gap: Check the spark plug gap using a spark plug gap tool. The correct gap for the MS 250 is typically around 0.020 inches (0.5 mm). Adjust the gap if necessary.
• Replacement: Replace the spark plug if it’s worn, damaged, or excessively fouled. I recommend using a spark plug specified for the MS 250, such as a Bosch WSR6F or NGK BPMR7A.

Tip 4: Proper Storage

• The Problem: Improper storage can lead to fuel degradation, carburetor problems, and other issues that make starting difficult.
• The Solution: Store your chainsaw properly when it’s not in use.
• Empty the Fuel Tank: If you’re not going to use the saw for an extended period (e.g., over the winter), empty the fuel tank. This prevents fuel from degrading and clogging the carburetor.
• Run the Carburetor Dry: After emptying the fuel tank, start the saw and let it run until it stalls. This ensures that the carburetor is empty.
• Clean the Saw: Clean the saw thoroughly, removing any sawdust or debris.
• Store in a Dry Place: Store the saw in a dry, well-ventilated place. Avoid storing it in direct sunlight or in a damp environment.

Tip 5: Carburetor Adjustment (Advanced)

• The Problem: An improperly adjusted carburetor can cause starting problems, poor performance, and excessive fuel consumption.
• The Solution: Adjust the carburetor if necessary. This is an advanced procedure, and I recommend consulting the owner’s manual or seeking professional help if you’re not comfortable doing it yourself.
• Locate the Adjustment Screws: The MS 250 typically has two or three adjustment screws: the high-speed (H) screw, the low-speed (L) screw, and sometimes an idle speed (LA) screw.
• Adjustment Procedure:
  • Start the Engine: Start the engine and let it warm up.
  • Low-Speed Screw (L): Turn the L screw clockwise until the engine starts to stall. Then, turn it counterclockwise until the engine runs smoothly at idle.
  • High-Speed Screw (H): This screw should only be adjusted by a qualified technician using a tachometer. Improper adjustment can damage the engine.
  • Idle Speed Screw (LA): Adjust the LA screw so that the chain does not move at idle.
• Important Note: Carburetor adjustment is a delicate process. Make small adjustments and observe the engine’s response. If you’re not sure what you’re doing, it’s best to seek professional help.

Troubleshooting Hacks: When the Starting Procedure Fails

Sometimes, even with the best intentions and a perfect starting procedure, your MS 250 might still refuse to start. Here are some troubleshooting hacks to help you diagnose and fix the problem.

Hack 1: Check for Spark

• The Problem: No spark means no ignition, and no ignition means no start.
• The Solution: Check if the spark plug is producing a spark.
• Procedure:
  • Remove the spark plug from the engine.
  • Reattach the spark plug wire to the spark plug.
  • Hold the spark plug against the engine block (grounding it).
  • Pull the starter cord.
  • Observe the spark plug. You should see a strong, blue spark jumping across the electrode.
• If There’s No Spark:
  • Check the spark plug wire for damage.
  • Check the ignition coil for damage.
  • Check the kill switch for proper function.
  • Replace the spark plug.
  • If none of these steps work, you may need to take the saw to a qualified technician.

Hack 2: Fuel Delivery Check

• The Problem: If fuel isn’t reaching the cylinder, the engine won’t start.
• The Solution: Check the fuel lines, fuel filter, and carburetor for blockages.
• Procedure:
  • Fuel Lines: Inspect the fuel lines for cracks, leaks, or kinks. Replace them if necessary.
  • Fuel Filter: The fuel filter is located inside the fuel tank, attached to the fuel line. Remove the fuel filter and inspect it. If it’s clogged, clean it or replace it.
  • Carburetor: If the fuel lines and filter are clear, the problem may be in the carburetor. The carburetor has small jets and passages that can become clogged with debris.
• Cleaning the Carburetor (Simple):
  • Remove the air filter.
  • Spray carburetor cleaner into the carburetor throat.
  • Pull the starter cord several times.
  • Try starting the engine.
• Carburetor Cleaning (Detailed):
  • Disassemble the carburetor.
  • Clean all the parts with carburetor cleaner.
  • Use compressed air to blow out the jets and passages.
  • Reassemble the carburetor.
  • This is a more involved process, and it’s best to consult the owner’s manual or seek professional help if you’re not comfortable doing it yourself.

Hack 3: Check the Compression

• The Problem: Low compression can prevent the engine from starting.
• The Solution: Check the engine’s compression.
• Procedure:
  • Remove the spark plug.
  • Insert a compression tester into the spark plug hole.
  • Pull the starter cord several times.
  • Read the compression gauge.
  • The MS 250 should have a compression reading of at least 120 PSI (pounds per square inch).
• If the Compression is Low:
  • Check the cylinder for damage.
  • Check the piston rings for wear.
  • Check the cylinder head gasket for leaks.
  • Low compression usually indicates a serious engine problem, and you may need to take the saw to a qualified technician.

Hack 4: The “Ether” Test (Use with Caution)

• The Problem: To quickly determine if the engine is having a fuel delivery problem.
• The Solution: Use starting fluid (ether) to bypass the fuel system.
• Procedure:
  • Remove the air filter.
  • Spray a small amount of starting fluid into the carburetor throat.
  • Pull the starter cord.
• If the Engine Starts Briefly: This indicates that the engine has spark and compression, but it’s not getting fuel. The problem is likely in the fuel system (fuel lines, fuel filter, or carburetor).
• If the Engine Still Doesn’t Start: This indicates that the problem is likely in the ignition system or the engine itself (spark plug, ignition coil, compression).
• Important Note: Use starting fluid sparingly and with caution. It’s highly flammable and can damage the engine if used excessively.

Hack 5: Check the Muffler

• The Problem: A clogged muffler can restrict exhaust flow, making starting difficult.
• The Solution: Check the muffler for blockages.
• Procedure:
  • Remove the muffler from the engine.
  • Inspect the muffler for carbon buildup or other obstructions.
  • Clean the muffler with a wire brush or by burning out the carbon.
  • Reinstall the muffler.

Hack 6: Examine the Flywheel Key

• The Problem: The flywheel key is a small metal piece that aligns the flywheel with the crankshaft. If it’s sheared or damaged, it can throw off the timing and prevent the engine from starting.
• The Solution: Inspect the flywheel key.
• Procedure:
  • Remove the starter assembly and the flywheel.
  • Locate the flywheel key. It’s a small metal piece that fits into a slot on the crankshaft and the flywheel.
  • Inspect the flywheel key for damage. If it’s sheared or bent, replace it.
  • Reinstall the flywheel and the starter assembly.

Hack 7: Vapor Lock Prevention

• The Problem: Vapor lock occurs when fuel in the fuel line or carburetor vaporizes due to excessive heat, preventing fuel from reaching the engine.
• The Solution: Take steps to prevent vapor lock.
• Prevention:
  • Use Fresh Fuel: Old fuel is more prone to vaporization.
  • Store the Saw in a Cool Place: Avoid storing the saw in direct sunlight or in a hot environment.
  • Allow the Saw to Cool Down: If the saw has been running for a long time, allow it to cool down before attempting to start it.
  • Wrap Fuel Lines: On older saws or in extremely hot conditions, consider wrapping the fuel lines with heat-resistant tape to insulate them from engine heat.

Preventative Maintenance: The Key to Easy Starting

The best way to avoid starting problems is to perform regular preventative maintenance. A well-maintained chainsaw is a reliable chainsaw. Here’s a maintenance schedule I recommend:

• Daily:
  • Check the chain for sharpness and tension.
  • Check the bar for wear and damage.
  • Clean the saw thoroughly.
• Weekly:
  • Clean the air filter.
  • Check the spark plug.
  • Check the fuel lines for leaks.
  • Grease the bar sprocket.
• Monthly:
  • Sharpen the chain.
  • Clean the carburetor.
  • Check the muffler for blockages.
  • Inspect the anti-vibration mounts.
• Annually:
  • Replace the fuel filter.
  • Replace the spark plug.
  • Have the saw professionally serviced.

By following this maintenance schedule, you can keep your MS 250 running smoothly and reliably for years to come.

Common Mistakes to Avoid

Even experienced chainsaw users can make mistakes that lead to starting problems. Here are some common mistakes to avoid:

• Using Old Fuel: As I’ve mentioned before, old fuel is a major cause of starting problems.
• Over-Priming the Carburetor: Over-priming can flood the engine, making it difficult to start.
• Using the Wrong Fuel Mixture: The MS 250 requires a 50:1 gasoline and oil mixture. Using the wrong mixture can damage the engine.
• Ignoring the Air Filter: A dirty air filter restricts airflow and can cause starting problems.
• Neglecting the Spark Plug: A fouled or worn spark plug can prevent the engine from starting.
• Improper Storage: Improper storage can lead to fuel degradation and other problems.
• Forcing the Starter Cord: Pulling the starter cord too hard can damage the starter mechanism.
• Ignoring Warning Signs: If the saw is running poorly or making unusual noises, don’t ignore the warning signs. Have it checked by a qualified technician.

Conclusion: Mastering the MS 250 Start

Starting a Stihl MS 250 can sometimes feel like an art form. However, by understanding the correct procedure, applying these pro tips, and knowing how to troubleshoot common issues, you can significantly increase your chances of a successful start every time. Remember, fresh fuel, a clean air filter, a healthy spark plug, and proper storage are your best allies in the battle against a stubborn chainsaw. And don’t forget the importance of preventative maintenance. A little bit of care and attention will go a long way in keeping your MS 250 running smoothly for years to come. Now, get out there and get sawing!

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