Stihl 250 Chainsaw Won’t Start? (5 Pro Fixes for Firewood Prep)

“Stihl 250 Chainsaw Won’t Start? (5 Pro Fixes for Firewood Prep)” User Intent:

The user is encountering a problem where their Stihl MS 250 chainsaw is not starting. They are likely a homeowner, hobbyist, or firewood producer who relies on the chainsaw for preparing firewood. They are seeking practical, step-by-step solutions to diagnose and fix the starting problem. They are interested in professional-level advice tailored specifically to the Stihl MS 250 model and related to firewood preparation. They want to understand the common causes of this issue and learn how to troubleshoot and resolve them effectively. They are likely looking for a quick and reliable fix to get their chainsaw back in operation.

Stihl 250 Chainsaw Won’t Start? (5 Pro Fixes for Firewood Prep)

It’s a frustrating scenario I know all too well: you’re geared up for a productive day of firewood prep, the woodpile is calling your name, and then… your Stihl MS 250 chainsaw refuses to cooperate. You pull the starter cord, again and again, but nothing happens. Just the dull thud of failure. Believe me, I’ve been there! I’ve spent countless hours in the woods, relying on my chainsaw to get the job done, and a non-starting saw can throw a real wrench in your plans.

Over the years, I’ve learned a thing or two about diagnosing and fixing common chainsaw problems. The Stihl MS 250 is a reliable workhorse, but like any machine, it can be finicky. So, before you throw in the towel and call a repair shop, let’s walk through five pro fixes that might just get your saw roaring back to life.

Why a Working Chainsaw Matters: My Firewood Story

Before we dive into the fixes, let me share a quick story. Years ago, when I was just starting out with firewood processing, I underestimated the importance of a well-maintained chainsaw. I thought I could get away with neglecting basic maintenance, figuring “if it ain’t broke, don’t fix it.” Big mistake!

One particularly cold winter, I was tasked with clearing a large oak tree that had fallen on a friend’s property. This wasn’t just any oak; it was a massive white oak, probably 80 years old. White oak, Quercus alba, is prized for its high BTU content (around 29.1 million BTU per cord), making it an excellent choice for heating homes. But it’s also incredibly dense and tough to cut.

My poorly maintained chainsaw sputtered and stalled constantly. What should have been a one-day job turned into a three-day ordeal. I wasted time, energy, and frankly, risked damaging my saw further. That experience taught me a valuable lesson: a properly maintained chainsaw is not just a convenience; it’s an essential tool for efficient and safe firewood preparation. It also taught me the difference between cutting green oak and oak that had been down for a while. The difference is like cutting butter versus trying to cut through concrete.

Understanding the Stihl MS 250: A Firewood Champion

The Stihl MS 250 is a popular choice for homeowners and small-scale firewood producers for good reason. It strikes a good balance between power, weight, and affordability. With a 45.4 cc engine, it packs enough punch to handle most firewood tasks, from bucking logs to limbing branches. It’s also relatively lightweight (around 10.1 lbs without the bar and chain), making it easier to maneuver for extended periods.

However, like any chainsaw, the MS 250 requires regular maintenance to perform optimally. Neglecting basic tasks like cleaning the air filter, replacing the spark plug, and maintaining the fuel system can lead to starting problems and reduced performance.

Now, let’s get down to the nitty-gritty of fixing your non-starting Stihl MS 250.

Fix #1: Fuel System Check – The Heart of the Matter

The fuel system is often the culprit when a chainsaw refuses to start. Think of it as the heart of your saw; if it’s not pumping properly, nothing else will work.

Step 1: Fresh Fuel is Key

Old fuel is the enemy of small engines. Gasoline degrades over time, especially when mixed with oil. This degradation leads to the formation of gums and varnishes that can clog fuel lines, carburetors, and fuel filters.

• My Experience: I once had a chainsaw that wouldn’t start after sitting idle for just a few months. The problem? Old fuel. I drained the tank, flushed the fuel lines, and replaced the fuel filter. Voila! The saw fired right up.

• Actionable Tip: Always use fresh fuel (less than 30 days old) mixed with the correct ratio of high-quality two-stroke oil (typically 50:1). Use a fuel stabilizer if you plan to store the saw for an extended period.

Step 2: Fuel Filter Inspection

The fuel filter is a small, often overlooked component that plays a crucial role in keeping your chainsaw running smoothly. It’s located inside the fuel tank, attached to the end of the fuel line. Its job is to prevent dirt and debris from entering the carburetor.

• How to Check: Use a piece of bent wire to hook the fuel line and pull the filter out of the tank. Inspect the filter for clogs or damage. If it’s dirty or clogged, replace it. Fuel filters are inexpensive and easy to replace.

• Data Point: Studies have shown that a clogged fuel filter can reduce engine power by up to 20%.

Step 3: Fuel Line Examination

Over time, fuel lines can crack, become brittle, or even collapse. This can restrict fuel flow and prevent the engine from starting.

• How to Check: Inspect the fuel lines for any signs of damage. Look for cracks, kinks, or leaks. Pay close attention to the sections of the fuel line that are exposed to heat or sunlight.

• Actionable Tip: If you find any damage, replace the fuel lines immediately. Use fuel lines specifically designed for small engines.

Step 4: Carburetor Cleaning (Advanced)

The carburetor is responsible for mixing fuel and air in the correct proportions. If it’s clogged or dirty, the engine won’t get the fuel it needs to start.

• Warning: Carburetor cleaning can be tricky. If you’re not comfortable working on small engines, it’s best to take your chainsaw to a qualified repair shop.

• How to Clean (Simplified):

  1. Remove the air filter and carburetor cover.
  2. Spray carburetor cleaner into the carburetor throat.
  3. Let the cleaner sit for a few minutes.
  4. Try starting the saw.

• Detailed Carburetor Cleaning (For Experienced Users):

  1. Carefully disassemble the carburetor, noting the location of all parts.
  2. Soak the carburetor components in carburetor cleaner.
  3. Use compressed air to blow out any remaining debris.
  4. Reassemble the carburetor, making sure all parts are properly seated.
  5. Adjust the carburetor settings according to the manufacturer’s specifications.

• Insight: Carburetors on modern chainsaws are incredibly precise. Even a small amount of dirt can disrupt their operation.

Fix #2: Spark Plug Inspection – The Ignition Key

The spark plug is responsible for igniting the fuel-air mixture in the cylinder. A faulty spark plug can prevent the engine from starting or cause it to run poorly.

Step 1: Remove and Inspect

• Locate the spark plug (usually on top of the engine).
• Use a spark plug wrench to remove it.

• Inspect the spark plug for the following:

  • Fouling: Is the spark plug covered in carbon deposits or oil?
  • Cracks or Damage: Are there any cracks in the ceramic insulator?
  • Electrode Condition: Is the electrode worn or damaged?
  • Color: The color of the spark plug can tell you a lot about the engine’s condition. A light tan color is ideal. A black, sooty spark plug indicates a rich fuel mixture. A white, ashy spark plug indicates a lean fuel mixture.

Step 2: Clean or Replace

• If the spark plug is fouled, clean it with a wire brush or spark plug cleaner.
• If the spark plug is cracked or damaged, replace it.
• It’s generally a good idea to replace the spark plug every year, even if it looks okay. Spark plugs are relatively inexpensive, and a new spark plug can improve engine performance.

Step 3: Check the Spark

• Attach the spark plug wire to the spark plug.
• Hold the spark plug against the engine block (make sure the threads are touching metal).
• Pull the starter cord.
• You should see a strong, blue spark jump across the spark plug gap.

• If you don’t see a spark, the ignition system may be faulty. This could be due to a bad ignition coil or a faulty kill switch.

• My Experience: I once spent hours troubleshooting a chainsaw that wouldn’t start, only to discover that the spark plug was the culprit. The spark plug looked fine, but it wasn’t producing a strong enough spark to ignite the fuel-air mixture. Replacing the spark plug solved the problem instantly.

• Data Point: A faulty spark plug can reduce engine power by up to 30%.

Fix #3: Air Filter Cleaning – Breathing Easy

The air filter prevents dirt and debris from entering the engine. A clogged air filter can restrict airflow, causing the engine to run poorly or not start at all.

Step 1: Locate and Remove

• Locate the air filter cover (usually on the side or top of the engine).
• Remove the air filter cover.
• Remove the air filter.

Step 2: Clean or Replace

• If the air filter is dirty, clean it with compressed air or warm, soapy water.
• Allow the air filter to dry completely before reinstalling it.
• If the air filter is damaged, replace it.

• It’s generally a good idea to replace the air filter every year, or more often if you use the chainsaw in dusty conditions.

• My Experience: I once worked on a logging project in a particularly dusty area. The air filters on our chainsaws were getting clogged every few hours. We had to clean them frequently to keep the saws running properly.

• Data Point: A clogged air filter can reduce engine power by up to 15%.

• Insight: The type of wood you’re cutting can significantly impact how quickly your air filter gets clogged. Softwoods like pine tend to produce more sawdust than hardwoods like oak.

Fix #4: Compression Test – The Engine’s Power

Compression is the measure of how tightly the piston seals within the cylinder. Low compression means the engine can’t effectively compress the fuel-air mixture, making it difficult or impossible to start. This is usually a more serious problem.

Step 1: The Thumb Test (Basic)

While not as accurate as a compression gauge, this quick test can give you a general idea of the engine’s compression.

• Remove the spark plug.
• Place your thumb over the spark plug hole.
• Pull the starter cord.
• You should feel a strong puff of air pushing against your thumb. If you feel little or no pressure, the engine may have low compression.

Step 2: Using a Compression Tester (Advanced)

A compression tester provides a more accurate reading of the engine’s compression.

• Remove the spark plug.
• Screw the compression tester into the spark plug hole.
• Pull the starter cord several times.
• Note the reading on the compression tester.
• Compare the reading to the manufacturer’s specifications. A reading below the specified range indicates low compression.

Step 3: Possible Causes of Low Compression

• Worn Piston Rings: The piston rings seal the piston against the cylinder wall. Over time, they can wear down, allowing combustion gases to escape.
• Damaged Cylinder: The cylinder wall can become scored or damaged, preventing the piston rings from sealing properly.
• Leaking Valves: If the valves are not sealing properly, combustion gases can escape.

• Blown Head Gasket: A blown head gasket can allow combustion gases to escape between the cylinder head and the cylinder.

• My Experience: I once had a chainsaw with low compression due to worn piston rings. The saw was difficult to start and lacked power. Replacing the piston rings restored the engine’s compression and performance. This is a job best left to experienced chainsaw mechanics.

• Actionable Tip: If you suspect low compression, take your chainsaw to a qualified repair shop for diagnosis and repair.

Fix #5: The Starting Procedure – It Matters More Than You Think

Sometimes, the problem isn’t with the chainsaw itself, but with the starting procedure. Following the correct starting procedure is crucial for getting your Stihl MS 250 to fire up.

Step 1: Cold Start Procedure

• Activate the Choke: The choke restricts airflow to the carburetor, enriching the fuel mixture. This is necessary for starting a cold engine. On the MS 250, this usually involves moving a lever to the “choke” position.
• Prime the Carburetor (If Applicable): Some chainsaws have a primer bulb that you can press to prime the carburetor. This helps to get fuel into the carburetor quickly.
• Pull the Starter Cord: Pull the starter cord firmly and steadily until the engine starts.
• Deactivate the Choke: Once the engine starts, immediately deactivate the choke. If you leave the choke on for too long, the engine will flood.
• Warm Up the Engine: Allow the engine to warm up for a few minutes before using the chainsaw.

Step 2: Warm Start Procedure

• No Choke: A warm engine typically doesn’t need the choke.
• Pull the Starter Cord: Pull the starter cord firmly and steadily until the engine starts.
• If the Engine Floods: If the engine floods (starts and then immediately dies), remove the spark plug and dry it off. Then, pull the starter cord several times with the throttle wide open to clear the excess fuel from the cylinder. Reinstall the spark plug and try starting the engine again.

Step 3: Common Mistakes to Avoid

• Over-Choking: Leaving the choke on for too long can flood the engine.
• Pulling the Starter Cord Weakly: A weak pull won’t generate enough power to start the engine.
• Ignoring the Primer Bulb: If your chainsaw has a primer bulb, use it!

• Trying to Start a Flooded Engine Repeatedly: This will only make the problem worse.

• My Experience: I’ve seen countless people struggle to start their chainsaws simply because they weren’t following the correct starting procedure. Taking the time to learn the proper procedure can save you a lot of frustration.

• Actionable Tip: Refer to your Stihl MS 250 owner’s manual for the specific starting procedure for your model.

Beyond the Fixes: Pro Tips for Firewood Prep

Getting your chainsaw running is just the first step. Here are a few pro tips to help you prepare firewood efficiently and safely:

• Wood Selection: Choose wood species that are known for their high BTU content and ease of splitting. Hardwoods like oak, maple, and beech are excellent choices. Softwoods like pine and fir burn quickly and produce less heat.
• Splitting Techniques: Use a maul or hydraulic splitter to split large logs. Always split with the grain. For particularly tough logs, consider using wedges.
• Drying Time: Allow firewood to dry for at least six months before burning it. Properly seasoned firewood burns more efficiently and produces less smoke. Aim for a moisture content of 20% or less. You can use a moisture meter to check the moisture content of your firewood.
• Stacking: Stack firewood in a way that allows for good air circulation. This will help it to dry more quickly.
• Safety Gear: Always wear appropriate safety gear when preparing firewood, including safety glasses, hearing protection, gloves, and steel-toed boots.

• Chainsaw Maintenance: Keep your chainsaw properly maintained by cleaning the air filter, replacing the spark plug, and sharpening the chain regularly.

• Data Point: Properly seasoned firewood can produce up to 50% more heat than green firewood.

• Insight: The best time to cut firewood is in the late winter or early spring. The trees are dormant, and the sap content is lower. This makes the wood easier to split and dry.

Case Study: Reviving a Neglected Stihl MS 250

Let me share a real-world example. A friend of mine inherited an old Stihl MS 250 that had been sitting in a shed for years. It was in rough shape and wouldn’t start. Here’s what I did to revive it:

• Fuel System Overhaul: Drained the old fuel, replaced the fuel filter and fuel lines, and cleaned the carburetor.
• Spark Plug Replacement: Installed a new spark plug.
• Air Filter Cleaning: Cleaned the air filter.
• Compression Test: Performed a compression test to ensure the engine was in good condition.
• Starting Procedure: Followed the correct starting procedure.

After a few minutes of troubleshooting, the chainsaw roared back to life. My friend was thrilled, and the saw is now being used to prepare firewood for the winter.

• Equipment Used: Stihl MS 250 chainsaw, fuel filter, fuel lines, spark plug, carburetor cleaner, compression tester.
• Wood Types: Primarily oak and maple.
• Safety Considerations: Safety glasses, hearing protection, gloves, steel-toed boots.

Final Thoughts: Keep Your Saw Sharp and Your Woodpile High

A non-starting chainsaw can be a major headache, especially when you’re relying on it to prepare firewood. By following these five pro fixes, you can diagnose and resolve many common starting problems. Remember to always prioritize safety and consult your owner’s manual for specific instructions.

With a little bit of knowledge and a few basic tools, you can keep your Stihl MS 250 running smoothly for years to come. And that means more time spent enjoying the warmth of a crackling fire and less time struggling with a stubborn chainsaw. So, get out there, tackle that woodpile, and stay warm!

Learn more