How to Start a Stihl MS250 (5 Pro Tips for Easy Ignition)

Imagine the crisp autumn air, the scent of pine needles underfoot, and the satisfying thunk of a well-split log landing on the growing woodpile. For me, that’s not just a chore; it’s a lifestyle. It’s about self-sufficiency, connection to nature, and the primal satisfaction of providing warmth for my family through the long winter months. And at the heart of it all is my trusty Stihl MS250 chainsaw.

I’ve spent years felling trees, bucking logs, and splitting firewood, and I’ve learned a thing or two about getting that MS250 roaring to life, even when it’s being stubborn. A balky chainsaw can turn a productive day into a frustrating ordeal. That’s why I’ve compiled these 5 pro tips, gleaned from my own experiences and countless hours of tinkering, to help you start your Stihl MS250 with ease.

5 Pro Tips for Easy Stihl MS250 Ignition

Starting a chainsaw, especially after it’s been sitting idle for a while, can sometimes feel like a battle. But with the right technique and a little know-how, you can get your Stihl MS250 running smoothly and reliably every time. These tips will focus on the common issues I’ve faced and the solutions I’ve found most effective.

1. Fuel Freshness and Mixture: The Foundation of Ignition

The first and most crucial step to easy starting is ensuring you have fresh, properly mixed fuel. Chainsaws, unlike your car, require a specific blend of gasoline and two-stroke oil. I cannot stress enough the importance of this.

Why Fresh Fuel Matters:

• Ethanol Degradation: Modern gasoline often contains ethanol, which can absorb moisture from the air. This moisture can lead to corrosion and fuel separation, especially in small engines. This is a killer for a chainsaw’s carburetor.
• Oil Separation: Over time, the two-stroke oil in your fuel mix can separate from the gasoline, leading to a lean fuel mixture. A lean mixture can cause engine damage due to insufficient lubrication.
• Gum and Varnish Buildup: Stale fuel can leave behind gummy deposits in the carburetor and fuel lines, restricting fuel flow.

My Fuel Mixing Ritual:

• Gasoline: I always use premium, ethanol-free gasoline whenever possible. If ethanol-free isn’t available, I add a fuel stabilizer to mitigate the effects of ethanol.
• Two-Stroke Oil: I strictly adhere to Stihl’s recommended oil-to-gas ratio, which is typically 50:1 for the MS250. Using the correct ratio is critical for engine longevity.
• Mixing Container: I use a dedicated fuel mixing container with clear markings for both gasoline and oil volumes. This ensures accurate mixing. I purchased a graduated container from a local hardware store for $15.
• Fuel Storage: I store my mixed fuel in a tightly sealed, approved fuel container in a cool, dark place. I never store mixed fuel for more than 30 days. After that, I dispose of it properly.

Pro Tip: I always write the date on the fuel container when I mix a new batch. This helps me keep track of its age and avoid using stale fuel. Consider using a fuel stabilizer like Sta-Bil or Sea Foam if you anticipate storing the fuel for longer periods. These products help prevent fuel degradation and keep the carburetor clean. I add 1 ounce of Sta-Bil per 2.5 gallons of fuel.

Actionable Metric: Track your fuel usage and disposal dates to ensure you’re always using fresh fuel. Aim to use up your mixed fuel within 30 days.

Takeaway: Fresh, properly mixed fuel is the cornerstone of easy starting. Don’t underestimate its importance.

2. Master the Starting Procedure: A Step-by-Step Guide

The Stihl MS250, like most chainsaws, has a specific starting procedure that needs to be followed precisely. Deviating from this procedure can lead to frustration and a flooded engine.

The Cold Start Sequence:

1. Engage the Chain Brake: Always engage the chain brake before starting the chainsaw. This prevents the chain from moving during the starting process, ensuring your safety. I always double-check the brake lever before pulling the cord.
2. Activate the Choke: Locate the choke lever on the side of the engine. For a cold start, move the choke lever to the fully closed position. This restricts airflow to the engine, creating a richer fuel mixture that aids in starting. The choke lever on the MS250 is usually marked with a symbol indicating the choke position.
3. Prime the Carburetor (if equipped): Some MS250 models have a priming bulb located near the carburetor. Press the priming bulb several times (usually 5-6 pumps) until you see fuel flowing through the clear fuel line. This draws fuel into the carburetor, making it easier to start. My older MS250 doesn’t have a priming bulb, but my newer one does.
4. Pull the Starter Cord: Place the chainsaw on a firm, level surface. Hold the handle firmly with one hand and pull the starter cord with the other. Pull the cord smoothly and deliberately, avoiding jerky motions. Pull until you hear the engine “pop” or briefly sputter. This indicates that the engine is trying to start. Usually, 3-5 pulls are enough.
5. Disengage the Choke (Half Choke): Once the engine “pops,” move the choke lever to the half-choke position (if your model has one). This allows more air to enter the engine.
6. Continue Pulling: Continue pulling the starter cord until the engine starts and runs smoothly. It may take a few more pulls.
7. Warm-up: Allow the engine to warm up for a few seconds before engaging the throttle. This allows the engine oil to circulate properly and ensures smooth operation.

The Warm Start Sequence:

If the engine is already warm, the starting procedure is slightly different:

1. Engage the Chain Brake: As always, engage the chain brake for safety.
2. No Choke: Do not use the choke for a warm start.
3. Pull the Starter Cord: Pull the starter cord until the engine starts. It should start much easier than a cold start.

Troubleshooting Starting Issues:

• Flooded Engine: If you’ve pulled the starter cord excessively without the engine starting, you may have flooded the engine with fuel. To clear a flooded engine, move the choke lever to the fully open position (no choke) and pull the starter cord several times. This will help to clear the excess fuel from the cylinder.
• Weak Spark: If the engine is not starting and you suspect a weak spark, remove the spark plug and inspect it. The spark plug should be clean and dry. If it’s fouled with carbon deposits or wet with fuel, clean or replace it.
• Fuel Line Issues: Check the fuel lines for cracks or leaks. Replace any damaged fuel lines.

Pro Tip: I find that a smooth, consistent pull on the starter cord is more effective than a quick, jerky pull. Imagine you’re trying to gently coax the engine to life rather than forcing it.

Actionable Metric: Practice the starting procedure until it becomes second nature. Time yourself to see how quickly you can start the chainsaw consistently.

Takeaway: Mastering the starting procedure is key to avoiding frustration and getting your Stihl MS250 running quickly.

3. Spark Plug Inspection and Maintenance: Igniting the Power

The spark plug is the heart of the ignition system. A faulty or fouled spark plug can prevent the engine from starting or cause it to run poorly. I’ve learned this the hard way after many frustrating mornings in the woods.

Why Spark Plugs Matter:

• Ignition: The spark plug provides the spark that ignites the fuel-air mixture in the cylinder, starting the combustion process.
• Engine Performance: A clean, properly gapped spark plug ensures optimal combustion, leading to better engine performance and fuel efficiency.
• Troubleshooting: Inspecting the spark plug can provide valuable clues about the engine’s overall health.

My Spark Plug Maintenance Routine:

• Inspection: I inspect the spark plug every 25 hours of use or at least once a season.
• Removal: To remove the spark plug, first, disconnect the spark plug wire. Then, use a spark plug wrench to loosen and remove the spark plug.
• Cleaning: If the spark plug is fouled with carbon deposits, I clean it with a wire brush or spark plug cleaner. You can also use a small file to clean the electrodes.
• Gapping: The spark plug gap is the distance between the center electrode and the side electrode. The correct spark plug gap for the Stihl MS250 is typically 0.020 inches (0.5 mm). I use a spark plug gapping tool to ensure the gap is correct.
• Replacement: If the spark plug is badly worn, cracked, or has damaged electrodes, I replace it with a new one. I always use the recommended spark plug for the Stihl MS250, which is typically a Bosch WSR6F or NGK BPMR7A.
• Installation: When installing the spark plug, I tighten it to the manufacturer’s recommended torque specification. Overtightening can damage the cylinder head.

Reading the Spark Plug:

The appearance of the spark plug can tell you a lot about the engine’s condition:

• Normal: A light tan or gray color indicates proper combustion.
• Fouled: A black, sooty deposit indicates a rich fuel mixture or excessive oil consumption.
• Oily: An oily deposit indicates excessive oil consumption or worn piston rings.
• White: A white or blistered appearance indicates a lean fuel mixture or overheating.

Pro Tip: I keep a spare spark plug in my chainsaw toolkit. This allows me to quickly replace a fouled spark plug in the field and get back to work.

Actionable Metric: Keep a log of your spark plug inspection and maintenance schedule. Replace the spark plug every 100 hours of use or annually, whichever comes first.

Takeaway: A healthy spark plug is essential for reliable starting and optimal engine performance. Don’t neglect this simple but crucial maintenance task.

4. Air Filter Cleaning and Replacement: Breathing Easy

A clean air filter is vital for proper engine operation. A clogged air filter restricts airflow to the engine, leading to reduced power, poor fuel economy, and difficulty starting. I’ve seen chainsaws rendered useless by a completely blocked air filter after just a few days of dusty work.

Why Air Filters Matter:

• Engine Protection: The air filter prevents dirt, dust, and debris from entering the engine, protecting it from wear and damage.
• Performance: A clean air filter allows the engine to breathe freely, maximizing power and fuel efficiency.
• Starting: A clogged air filter can make the engine difficult to start.

My Air Filter Maintenance Routine:

• Inspection: I inspect the air filter every 10 hours of use or more frequently in dusty conditions.
• Removal: To remove the air filter, first, locate the air filter cover on the side of the engine. Remove the cover and carefully remove the air filter.
• Cleaning: I clean the air filter by tapping it gently to remove loose dirt and debris. I then wash it with warm, soapy water. Rinse the filter thoroughly and allow it to air dry completely before reinstalling it.
• Replacement: If the air filter is damaged, excessively dirty, or cannot be cleaned effectively, I replace it with a new one. I always use the recommended air filter for the Stihl MS250.
• Installation: When installing the air filter, make sure it is properly seated and that the air filter cover is securely fastened.

Pro Tip: I keep a spare air filter on hand so I can quickly replace a dirty filter in the field. I also use a pre-filter wrap to extend the life of the air filter.

Actionable Metric: Track your air filter cleaning and replacement schedule. Clean the air filter every 10 hours of use and replace it every 50 hours or annually, whichever comes first.

Takeaway: A clean air filter is essential for optimal engine performance and easy starting. Make air filter maintenance a regular part of your chainsaw maintenance routine.

5. Carburetor Adjustments (If Necessary): Fine-Tuning for Performance

The carburetor is responsible for mixing the fuel and air in the correct proportions for combustion. If the carburetor is not properly adjusted, the engine may be difficult to start, run poorly, or stall frequently. I’ve only had to adjust the carburetor on my MS250 a couple of times, but it made a world of difference.

When to Adjust the Carburetor:

• Difficulty Starting: If the engine is consistently difficult to start, even after following the other troubleshooting steps.
• Poor Idle: If the engine idles roughly or stalls frequently.
• Poor Performance: If the engine lacks power or hesitates when accelerating.
• Altitude Changes: If you’re operating the chainsaw at a significantly different altitude than where it was originally tuned.

Carburetor Adjustment Screws:

The Stihl MS250 carburetor typically has three adjustment screws:

• L (Low-Speed): Adjusts the fuel mixture at idle and low speeds.
• H (High-Speed): Adjusts the fuel mixture at high speeds.
• LA (Idle Speed): Adjusts the engine’s idle speed.

Carburetor Adjustment Procedure:

Important Note: Carburetor adjustments should only be performed by someone with experience and a good understanding of small engine mechanics. Incorrect adjustments can damage the engine. If you’re not comfortable performing these adjustments yourself, take your chainsaw to a qualified service technician. I highly recommend watching a few YouTube videos from reputable sources before attempting this.

1. Warm-up: Start the engine and allow it to warm up to operating temperature.
2. Idle Speed Adjustment: Turn the LA screw clockwise to increase the idle speed or counterclockwise to decrease it. Adjust the idle speed until the engine runs smoothly without stalling. The chain should not be moving at idle. The ideal idle speed for the MS250 is around 2,800 RPM.
3. Low-Speed Adjustment: Turn the L screw clockwise to lean the fuel mixture or counterclockwise to richen it. Adjust the L screw until the engine idles smoothly and responds quickly to throttle inputs.
4. High-Speed Adjustment: Turn the H screw clockwise to lean the fuel mixture or counterclockwise to richen it. Adjust the H screw until the engine runs smoothly at high speeds without bogging down or hesitating.

Pro Tip: I use a tachometer to accurately measure the engine’s RPM during carburetor adjustments. This helps me to fine-tune the carburetor for optimal performance. A decent tachometer can be purchased online for around $30.

Actionable Metric: Monitor your engine’s performance after making carburetor adjustments. Check the spark plug regularly to ensure the fuel mixture is correct.

Takeaway: Carburetor adjustments can fine-tune your chainsaw’s performance, but they should be performed with caution and expertise.

Beyond the Basics: Additional Tips for Reliable Starting

While the 5 pro tips above cover the most common causes of starting problems, here are a few additional tips to keep in mind:

• Fuel Filter: The fuel filter is located inside the fuel tank and filters the fuel before it reaches the carburetor. A clogged fuel filter can restrict fuel flow and make the engine difficult to start. I replace the fuel filter annually.
• Fuel Lines: Inspect the fuel lines regularly for cracks or leaks. Replace any damaged fuel lines. I use a fuel line pick to easily remove and install fuel lines.
• Muffler Screen: The muffler screen prevents sparks from exiting the muffler. A clogged muffler screen can restrict exhaust flow and reduce engine power. Clean the muffler screen periodically with a wire brush.
• Compression: Low compression can make the engine difficult to start. If you suspect low compression, have the engine professionally tested.
• Storage: When storing the chainsaw for extended periods, drain the fuel tank and run the engine until it stalls to remove any remaining fuel from the carburetor. This will prevent fuel from gumming up the carburetor during storage. I also remove the spark plug and add a small amount of oil to the cylinder to prevent corrosion.

Safety First:

Always wear appropriate safety gear when operating a chainsaw, including:

• Eye Protection: Safety glasses or a face shield to protect your eyes from flying debris.
• Hearing Protection: Earplugs or earmuffs to protect your hearing from the loud engine noise.
• Gloves: Work gloves to protect your hands.
• Chaps: Chainsaw chaps to protect your legs from accidental cuts.
• Steel-Toed Boots: Steel-toed boots to protect your feet.

My Personal Chainsaw Story:

I remember one particularly cold winter morning when my MS250 refused to start. I had a pile of firewood to cut, and the temperature was dropping rapidly. I went through all the usual troubleshooting steps – fresh fuel, spark plug check, air filter cleaning – but nothing seemed to work. Frustrated and cold, I was about to give up when I decided to take a closer look at the fuel line. I noticed a small crack near the carburetor. I replaced the fuel line, and the chainsaw started on the first pull. That experience taught me the importance of thoroughly inspecting all the components of the fuel system.

Conclusion:

Starting a Stihl MS250 doesn’t have to be a struggle. By following these 5 pro tips and practicing proper maintenance, you can ensure that your chainsaw starts reliably every time. Remember to prioritize safety and always wear appropriate protective gear. With a little patience and attention to detail, you can keep your MS250 running smoothly for years to come, providing you with the power you need to tackle any wood-cutting task. Now, get out there and make some sawdust!

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