Stihl MS250 Start Trouble (5 Expert Fixes For Chainsaw Owners)

Have you ever yanked on the starter cord of your Stihl MS250, expecting that familiar roar, only to be met with frustrating silence? Or worse, a sputter that dies just as quickly as it ignites? I know I have. It’s a feeling that every chainsaw owner dreads, especially when you’re in the middle of a big firewood project or tackling some storm cleanup. The Stihl MS250 is a reliable workhorse, but even the best machines can be finicky sometimes.

Over the years, I’ve spent countless hours in the woods, felling trees, bucking logs, and splitting firewood. I’ve learned that a chainsaw that won’t start is more than just an inconvenience; it can throw off your entire schedule and even be a safety hazard if you’re relying on it in a remote location. That’s why I’ve put together this guide to help you diagnose and fix the most common starting problems with your Stihl MS250.

In this article, I’ll share my expert fixes for chainsaw owners. We’ll dive deep into troubleshooting techniques, preventative maintenance tips, and even a bit of wood science to help you understand why your chainsaw might be acting up. Let’s get that saw roaring again!

Understanding the Stihl MS250: A Brief Overview

Before we dive into the fixes, let’s take a moment to appreciate the Stihl MS250. This chainsaw is a popular choice for homeowners and occasional users because it strikes a great balance between power, weight, and price. It’s powerful enough to handle most household tasks, like cutting firewood or pruning trees, but it’s also light enough to use for extended periods without excessive fatigue.

The MS250 is powered by a 45.4 cc two-stroke engine, which means it requires a mix of gasoline and oil to run properly. It also features a side-access chain tensioner, which makes it easy to adjust the chain tension without having to remove the chain cover.

Why the MS250 is a Great Chainsaw

Versatility: Ideal for a range of tasks, from cutting small trees to preparing firewood.
Ease of Use: Lightweight and easy to handle, even for beginners.
Reliability: Known for its durability and consistent performance.

Common Issues with the MS250

Despite its reputation for reliability, the MS250 can experience starting problems. These issues often stem from fuel-related problems, ignition issues, or simple wear and tear.

Expert Fix #1: Fuel System Check and Cleaning

One of the most common reasons a Stihl MS250 won’t start is a problem with the fuel system. Fuel issues can range from old or contaminated fuel to clogged fuel filters or carburetors. Here’s how to tackle these problems:

1. Check the Fuel Mix

Two-stroke engines like the one in the MS250 require a precise mix of gasoline and oil. Using the wrong ratio or old fuel can cause starting problems and even damage the engine.

The Correct Fuel Mix: Stihl recommends a 50:1 fuel-to-oil ratio for the MS250. This means you should mix 50 parts of gasoline with 1 part of two-stroke oil. I always use high-quality, name-brand two-stroke oil to ensure proper lubrication and minimize carbon buildup.

Why the Right Mix Matters: Too much oil can cause the engine to run poorly and produce excessive smoke. Too little oil can lead to engine damage due to insufficient lubrication.

My Experience: I once made the mistake of using old fuel that had been sitting in my garage for over a year. The chainsaw refused to start, and when I finally got it running, it ran rough and sputtered. I learned my lesson the hard way: always use fresh fuel!

2. Inspect and Replace the Fuel Filter

The fuel filter is a small, inexpensive part that prevents debris from entering the carburetor. A clogged fuel filter can restrict fuel flow and cause starting problems.

How to Check the Fuel Filter:

Locate the fuel filter inside the fuel tank. It’s usually attached to the end of the fuel line.
Use a clean wire or hook to pull the fuel filter out of the tank.
Inspect the filter for dirt, debris, or clogs.
If the filter is dirty, replace it with a new one. Fuel filters are cheap and easy to replace, so it’s a good idea to keep a few on hand.

Pro Tip: I recommend replacing the fuel filter at least once a year, or more often if you use your chainsaw frequently.

3. Clean the Carburetor

The carburetor is responsible for mixing air and fuel in the correct proportions. A dirty or clogged carburetor can cause a variety of problems, including starting difficulties, poor performance, and stalling.

Understanding the Carburetor: The carburetor has several small jets and passages that can easily become clogged with varnish or debris.

How to Clean the Carburetor:

Remove the Air Filter: Start by removing the air filter cover and taking out the air filter.
Remove the Carburetor: Carefully disconnect the fuel lines and throttle linkage from the carburetor. Then, remove the carburetor from the engine.
Disassemble the Carburetor: Disassemble the carburetor, taking note of the location of each part. I recommend taking photos as you go to help you reassemble it correctly.
Clean the Parts: Use carburetor cleaner to clean all the parts of the carburetor. Pay special attention to the jets and passages. You can use a small wire or a carburetor cleaning tool to clear any clogs.
Reassemble the Carburetor: Reassemble the carburetor, making sure all the parts are in the correct locations.
Reinstall the Carburetor: Reinstall the carburetor on the engine, reconnect the fuel lines and throttle linkage, and replace the air filter.

My Experience: I once had a chainsaw that would start but would immediately die. After cleaning the carburetor, I found a tiny piece of debris blocking one of the jets. Once I cleared the clog, the chainsaw ran like new.

4. Check the Fuel Lines

Cracked or damaged fuel lines can leak air, which can prevent the engine from starting.

How to Check the Fuel Lines: Inspect the fuel lines for cracks, leaks, or damage. If you find any problems, replace the fuel lines.

Pro Tip: Fuel lines can dry out and crack over time, especially if they’re exposed to sunlight or extreme temperatures. I recommend replacing the fuel lines every few years as part of your routine maintenance.

Expert Fix #2: Ignition System Inspection

If the fuel system is working properly, the next thing to check is the ignition system. The ignition system is responsible for creating the spark that ignites the fuel-air mixture in the engine.

1. Check the Spark Plug

The spark plug is a critical component of the ignition system. A fouled or damaged spark plug can prevent the engine from starting.

How to Check the Spark Plug:

Remove the Spark Plug: Disconnect the spark plug wire and use a spark plug wrench to remove the spark plug from the engine.
Inspect the Spark Plug: Inspect the spark plug for cracks, damage, or excessive carbon buildup. The electrode should be clean and dry.
Clean or Replace the Spark Plug: If the spark plug is dirty, you can try cleaning it with a wire brush. However, if the spark plug is damaged or excessively worn, it’s best to replace it with a new one.

Understanding Spark Plug Condition:

Black and Sooty: Indicates a rich fuel mixture or excessive oil.
Wet: Indicates flooding or a fuel leak.
White or Light Gray: Indicates a lean fuel mixture.

Pro Tip: I always keep a spare spark plug in my toolbox. It’s a cheap and easy way to ensure that I can get my chainsaw running in a pinch.

2. Test for Spark

Even if the spark plug looks good, it may not be producing a strong enough spark to ignite the fuel-air mixture.

How to Test for Spark:

Reattach the Spark Plug Wire: Reattach the spark plug wire to the spark plug.
Ground the Spark Plug: Hold the spark plug against the engine block or another metal part of the chainsaw.
Pull the Starter Cord: Pull the starter cord and watch for a spark at the tip of the spark plug.
Check for a Strong Blue Spark: A strong, blue spark indicates that the ignition system is working properly. A weak or nonexistent spark indicates a problem with the ignition system.

My Experience: I once had a chainsaw that wouldn’t start, even after replacing the spark plug. After testing for spark, I discovered that the ignition coil was bad. Replacing the ignition coil solved the problem.

3. Inspect the Ignition Coil

The ignition coil is responsible for generating the high-voltage electricity that creates the spark. A faulty ignition coil can prevent the engine from starting.

How to Inspect the Ignition Coil:

Check the Wiring: Inspect the wiring to the ignition coil for damage or loose connections.
Test the Ignition Coil with a Multimeter: Use a multimeter to test the resistance of the ignition coil. If the resistance is outside the specified range, the ignition coil may be bad.

Pro Tip: Testing the ignition coil with a multimeter can be tricky. If you’re not comfortable doing it yourself, it’s best to take your chainsaw to a qualified repair shop.

Expert Fix #3: Compression Test

Compression is essential for the engine to ignite the fuel-air mixture. Low compression can be caused by worn piston rings, a damaged cylinder, or a leaky valve.

How to Perform a Compression Test

Remove the Spark Plug: Remove the spark plug from the engine.
Insert the Compression Tester: Screw the compression tester into the spark plug hole.
Pull the Starter Cord: Pull the starter cord several times while watching the gauge on the compression tester.
Record the Reading: Record the highest reading on the gauge.

Interpreting the Results

Low Compression: If the compression reading is below the manufacturer’s specification, the engine may have worn piston rings, a damaged cylinder, or a leaky valve.
Normal Compression: If the compression reading is within the manufacturer’s specification, the engine’s compression is likely good.

Data Point: A healthy Stihl MS250 should have a compression reading of around 120-150 PSI (pounds per square inch).

Addressing Low Compression

If the compression test reveals low compression, you may need to rebuild or replace the engine. This is a more complex repair that may require the assistance of a qualified mechanic.

My Experience: I once had a chainsaw that was difficult to start and lacked power. After performing a compression test, I discovered that the engine had very low compression. I ended up rebuilding the engine, which involved replacing the piston rings and honing the cylinder. After the rebuild, the chainsaw ran like new.

Expert Fix #4: Checking and Cleaning the Air Filter

A clogged air filter can restrict airflow to the engine, causing it to run poorly or not start at all.

Why a Clean Air Filter Matters

The air filter prevents dirt and debris from entering the engine. A clogged air filter can reduce engine performance and even damage the engine over time.

How to Check and Clean the Air Filter

Locate the Air Filter: The air filter is usually located under a cover on top of the engine.
Remove the Air Filter: Remove the air filter cover and take out the air filter.
Inspect the Air Filter: Inspect the air filter for dirt, debris, or damage.
Clean the Air Filter: If the air filter is dirty, you can clean it with soap and water. Allow the air filter to dry completely before reinstalling it. If the air filter is damaged, replace it with a new one.

Pro Tip: I recommend cleaning the air filter after every few uses, or more often if you’re working in dusty conditions.

Types of Air Filters

Foam Filters: These filters are washable and reusable.
Paper Filters: These filters are disposable and should be replaced when they become dirty.

My Experience: I once had a chainsaw that would start but would immediately die. After checking the air filter, I found that it was completely clogged with sawdust. Cleaning the air filter solved the problem.

Expert Fix #5: Proper Starting Procedure

Sometimes, the problem isn’t with the chainsaw itself, but with the starting procedure. Here’s the correct way to start a Stihl MS250:

Step-by-Step Starting Guide

Engage the Chain Brake: Make sure the chain brake is engaged to prevent the chain from moving during starting.
Activate the Choke: If the engine is cold, activate the choke. The choke restricts airflow to the engine, which makes the fuel mixture richer and easier to ignite.
Prime the Carburetor: Press the primer bulb several times to prime the carburetor. This helps to draw fuel into the carburetor and make it easier to start the engine.
Pull the Starter Cord: Pull the starter cord firmly and steadily until the engine starts.
Deactivate the Choke: Once the engine starts, deactivate the choke.
Let the Engine Warm Up: Allow the engine to warm up for a few minutes before using the chainsaw.

Troubleshooting Starting Issues

Engine Won’t Start: Make sure the fuel tank is full, the spark plug is clean, and the air filter is clean.
Engine Starts but Dies Immediately: Check the fuel lines for leaks and clean the carburetor.
Engine Runs Rough: Check the spark plug and air filter.

My Experience: I once spent hours trying to start a chainsaw, only to realize that I had forgotten to deactivate the chain brake. Once I released the chain brake, the chainsaw started right up.

Preventative Maintenance: Keeping Your MS250 in Top Shape

Preventative maintenance is the key to keeping your Stihl MS250 running smoothly and avoiding starting problems. Here are some essential maintenance tips:

Regular Cleaning

Clean your chainsaw after every use to remove sawdust, debris, and oil. Pay special attention to the air filter, spark plug, and carburetor.

Proper Storage

Store your chainsaw in a dry, protected location. Drain the fuel tank before storing the chainsaw for extended periods.

Chain Maintenance

Keep the chain sharp and properly tensioned. A dull or loose chain can put extra strain on the engine and cause starting problems.

Professional Servicing

Have your chainsaw professionally serviced at least once a year. A qualified mechanic can inspect the chainsaw for wear and tear and perform any necessary repairs.

Wood Science: Understanding Your Fuel Source

Understanding the properties of wood can also help you troubleshoot chainsaw problems. Different types of wood have different densities and moisture contents, which can affect how easily they cut and how much strain they put on the engine.

Hardwood vs. Softwood

Hardwood: Hardwood comes from deciduous trees, such as oak, maple, and cherry. Hardwood is denser and more difficult to cut than softwood.
Softwood: Softwood comes from coniferous trees, such as pine, fir, and spruce. Softwood is less dense and easier to cut than hardwood.

Moisture Content

The moisture content of wood can also affect how easily it cuts. Green wood (freshly cut wood) has a high moisture content, which can make it more difficult to cut. Seasoned wood (wood that has been allowed to dry) has a lower moisture content, which makes it easier to cut.

Data Point: Freshly cut wood can have a moisture content of 50% or more, while seasoned wood typically has a moisture content of 20% or less.

Impact on Chainsaw Performance

Cutting green wood can put extra strain on the engine and cause it to overheat. It can also dull the chain more quickly. Cutting seasoned wood is easier on the engine and the chain.

Logging Tool Selection and Maintenance Best Practices

Choosing the right logging tools and maintaining them properly can also help you avoid chainsaw problems.

Essential Logging Tools

Felling Axe: Used for felling trees.
Cant Hook: Used for rolling logs.
Peavey: Used for moving logs.
Wedges: Used for splitting wood.

Tool Maintenance

Keep your logging tools sharp and in good condition. A dull axe or a damaged cant hook can be dangerous and make your work more difficult.

Firewood Seasoning Techniques and Safety Considerations

Properly seasoning firewood is essential for efficient burning and reducing creosote buildup in your chimney.

Seasoning Techniques

Stacking: Stack firewood in a single row, with space between the rows for air circulation.
Elevation: Elevate the firewood off the ground to prevent moisture from wicking up into the wood.
Covering: Cover the top of the firewood pile to protect it from rain and snow.

Safety Considerations

Wear Safety Gear: Always wear safety glasses, gloves, and hearing protection when cutting and splitting firewood.
Be Aware of Your Surroundings: Be aware of your surroundings and watch out for hazards, such as falling branches or uneven terrain.
Use Proper Lifting Techniques: Use proper lifting techniques to avoid back injuries.

Project Planning and Execution

Planning your wood processing projects can help you work more efficiently and safely.

Planning Steps

Assess the Site: Assess the site and identify any hazards, such as power lines or steep slopes.
Develop a Plan: Develop a plan for felling trees, bucking logs, and splitting firewood.
Gather Your Tools: Gather your tools and make sure they are in good working condition.
Follow Safety Procedures: Follow all safety procedures to prevent accidents.

Conclusion: Getting Back to Work

A Stihl MS250 that won’t start can be a frustrating problem, but with a systematic approach and a little know-how, you can usually diagnose and fix the issue yourself. Remember to start with the basics: check the fuel system, ignition system, and air filter. If those checks don’t reveal the problem, perform a compression test. And don’t forget the importance of proper starting procedures and preventative maintenance.

By following the expert fixes and tips outlined in this article, you’ll be well-equipped to keep your Stihl MS250 running smoothly for years to come. Now get out there and get to work!

Next Steps

Review Your Chainsaw’s Manual: Always refer to your Stihl MS250 owner’s manual for specific instructions and safety guidelines.
Gather Your Tools: Make sure you have the necessary tools and supplies for troubleshooting and repairs.
Start Troubleshooting: Follow the steps outlined in this article to diagnose and fix the problem.
Seek Professional Help: If you’re not comfortable performing the repairs yourself, take your chainsaw to a qualified repair shop.

By taking these steps, you’ll be well on your way to getting your Stihl MS250 back in action and tackling your wood processing projects with confidence.