Stihl MS 270 Chainsaw Troubleshooting (5 Expert Fixes)

Do you find yourself drawn to the comforting crackle of a wood-burning stove on a chilly evening? Or perhaps you’re someone who appreciates the rewarding labor of transforming raw timber into neatly stacked firewood? Whatever your reason, if you own a Stihl MS 270 chainsaw, you’re likely nodding along. It’s a workhorse of a machine, a true friend in the woodlot. But even the most reliable equipment can sometimes throw a wrench in the works. That’s where I come in.

Over the years, I’ve spent countless hours in the woods, felling trees, bucking logs, and splitting firewood. I’ve seen it all – from perfectly seasoned oak to stubborn, knotty elm. And I’ve learned a thing or two about keeping my equipment, especially my trusty Stihl MS 270, running smoothly. I’ve experienced the frustration of a chainsaw that won’t start on a cold morning, the annoyance of a chain that dulls too quickly, and the downright panic of a saw that suddenly quits mid-cut.

This guide isn’t just a collection of generic troubleshooting tips. It’s a compilation of the real-world solutions I’ve discovered, often through trial and error (and a few choice words muttered in the solitude of the forest). I’ll share my experiences, the data I’ve collected, and the techniques I’ve honed to help you diagnose and fix common issues with your Stihl MS 270.

I’ll break down the problems into easy-to-understand steps, arming you with the knowledge to get your saw back up and running, so you can get back to the satisfaction of a job well done. Let’s dive in.

Stihl MS 270 Chainsaw Troubleshooting: 5 Expert Fixes

1. The Stubborn Starter: When Your MS 270 Refuses to Roar

There’s nothing more frustrating than a chainsaw that won’t start. You pull, you pull again, and still nothing. The engine just coughs mockingly. Before you resign yourself to a day of manual labor, let’s explore some common culprits and their solutions.

The Culprit: Fuel Issues

Why it matters: The Stihl MS 270, like most two-stroke engines, requires a precise mixture of gasoline and oil. Old or improperly mixed fuel is a common reason for starting problems. Ethanol-blended gasoline can also wreak havoc, absorbing moisture and leading to fuel separation.

My Experience: I once spent an entire morning battling a stubborn MS 270. I had mixed a fresh batch of fuel, or so I thought. Turns out, I had grabbed the wrong container and accidentally used straight gasoline. The saw sputtered and coughed, refusing to start. A quick drain and refill with the correct mixture solved the problem.

The Fix:

• Step 1: Fuel Check: Drain the fuel tank and inspect the fuel. Does it smell stale? Is it cloudy or discolored? If so, discard it properly (check your local regulations for proper disposal) and mix a fresh batch of fuel using a high-quality two-stroke oil at the manufacturer-recommended ratio (usually 50:1). I always use a fuel stabilizer, especially if I know the saw will be sitting idle for a while.
  • Data Point: Using fuel older than 30 days can reduce engine performance by up to 20% and increase the risk of engine damage.
• Step 2: Fuel Filter Inspection: The fuel filter sits inside the fuel tank, attached to the fuel line. It prevents debris from entering the carburetor. If it’s clogged, it will restrict fuel flow.
  • Procedure: Use a hooked wire to carefully pull the fuel filter out of the tank. Inspect it for dirt, debris, or signs of deterioration. Replace the filter if it’s dirty or damaged.
  • Tool Requirement: Hooked wire or specialized fuel filter removal tool.
  • Specification: Replace the fuel filter annually or after every 50 hours of use, whichever comes first.
• Step 3: Carburetor Cleaning: The carburetor mixes air and fuel to create a combustible mixture. If it’s clogged with varnish or deposits, it can prevent the engine from starting.
  • Procedure: This is a more involved process, requiring some mechanical aptitude. I recommend consulting the Stihl MS 270 service manual for detailed instructions. However, the basic steps involve removing the air filter, spraying carburetor cleaner into the carburetor throat, and allowing it to soak for a few minutes. You may also need to remove the carburetor and clean it more thoroughly.
  • Safety Code: Always disconnect the spark plug wire before working on the carburetor to prevent accidental starting.
  • Material Specification: Use only carburetor cleaner specifically designed for two-stroke engines.
  • Technical Limitation: Carburetor cleaning may require adjusting the carburetor settings afterwards. If you’re not comfortable with this, take the saw to a qualified technician.

The Culprit: Spark Issues

Why it matters: The spark plug ignites the air-fuel mixture in the cylinder. A faulty spark plug will prevent the engine from starting.

The Fix:

• Step 1: Spark Plug Inspection: Remove the spark plug and inspect it. Look for signs of fouling (carbon buildup), cracking, or damage to the electrode.
  • Procedure: Disconnect the spark plug wire, then use a spark plug wrench to remove the spark plug.
  • Tool Requirement: Spark plug wrench.
  • Specification: The spark plug gap should be 0.5mm (0.020 inches).
  • Data Point: A fouled spark plug can reduce engine power by up to 15%.
• Step 2: Spark Test: Reconnect the spark plug wire to the spark plug. Hold the spark plug against the engine block and pull the starter cord. You should see a strong, blue spark. If the spark is weak or non-existent, replace the spark plug.
  • Safety Code: Wear insulated gloves when performing a spark test to avoid electrical shock.
• Step 3: Ignition Module: If the spark plug is good and you’re still not getting a spark, the ignition module may be faulty. This is a more complex repair that may require professional assistance.

The Culprit: Compression Issues

Why it matters: The engine needs adequate compression to create the heat necessary for combustion. Low compression can be caused by worn piston rings, a damaged cylinder, or a leaky head gasket.

The Fix:

• Compression Test: A compression test measures the pressure inside the cylinder.
  • Procedure: Remove the spark plug and screw a compression tester into the spark plug hole. Pull the starter cord several times and note the reading on the tester.
  • Tool Requirement: Compression tester.
  • Specification: A healthy Stihl MS 270 should have a compression reading of at least 120 PSI.
  • Technical Limitation: Performing a compression test requires specialized equipment. If you don’t have a compression tester, take the saw to a qualified technician.
• Professional Assistance: If the compression is low, the engine may require a major overhaul. This is best left to a qualified technician.

2. The Dull Chain Dilemma: Maintaining Peak Cutting Performance

A dull chain is not only frustrating, but it’s also dangerous. It requires more effort to cut, increases the risk of kickback, and puts unnecessary strain on the engine. Keeping your chain sharp is crucial for efficient and safe operation.

The Culprit: Improper Sharpening Technique

Why it matters: Sharpening a chainsaw chain isn’t just about grinding away metal. It’s about maintaining the correct angles and depth gauges to ensure optimal cutting performance.

My Experience: I learned the hard way about the importance of proper sharpening. I used to just grind away at the chain until it looked “sharp.” But my cuts were always slow and ragged. It wasn’t until I took a chainsaw sharpening class that I learned the proper techniques and the importance of maintaining the correct angles.

The Fix:

• Step 1: Understanding Chain Anatomy: A chainsaw chain consists of cutters, tie straps, and drive links. The cutters are the teeth that do the actual cutting. Each cutter has a top plate cutting angle, a side plate cutting angle, and a depth gauge.
  • Visual Example: (Include a diagram of a chainsaw chain cutter, labeling the top plate cutting angle, side plate cutting angle, and depth gauge).
• Step 2: Choosing the Right Sharpening Tool: There are several options for sharpening a chainsaw chain, including:
  • Round File and File Guide: This is the most common and affordable method. It requires some practice to master, but it allows for precise sharpening.
    • Tool Requirement: Round file (size specific to your chain pitch), file guide, depth gauge tool.
    • Specification: Use a round file that matches the pitch of your chain. The Stihl MS 270 typically uses a 3/8″ pitch chain, requiring a 5/32″ round file.
  • Electric Chainsaw Sharpener: This is a faster and easier method, but it can be more aggressive and prone to over-sharpening.
    • Tool Requirement: Electric chainsaw sharpener.
    • Specification: Ensure the sharpener is compatible with your chain pitch.
  • Bench Grinder: This is the most precise method, but it requires specialized equipment and experience.
    • Tool Requirement: Bench grinder with chainsaw sharpening attachment.
    • Specification: Use a grinding wheel specifically designed for chainsaw chains.
• Step 3: Sharpening Procedure:
  • Secure the Chain: Use a vise to secure the chain.
  • File at the Correct Angle: Using the file guide, file each cutter at the correct top plate and side plate angles. The angles are typically marked on the file guide.
    • Data Point: Maintaining the correct sharpening angles can increase chain life by up to 30%.
  • Maintain Depth Gauge: Use the depth gauge tool to file down the depth gauges to the correct height.
    • Specification: The depth gauge should be approximately 0.025″ below the top of the cutter.
  • Sharpen Each Cutter Equally: Sharpen each cutter the same number of strokes to ensure they are all the same length.
  • Clean the Chain: After sharpening, clean the chain with a brush to remove any filings.

The Culprit: Improper Chain Tension

Why it matters: A chain that is too loose can derail, while a chain that is too tight can overheat and damage the bar and chain.

The Fix:

• Step 1: Tensioning Procedure:
  • Loosen the Bar Nuts: Loosen the bar nuts slightly.
  • Adjust the Tensioning Screw: Use the tensioning screw to adjust the chain tension. The chain should be snug against the bar but still able to be pulled around by hand.
  • Tighten the Bar Nuts: Tighten the bar nuts securely.
  • Specification: The chain should have approximately 1/8″ of slack.
  • Practical Tip: Check the chain tension frequently, especially when the chain is new.

The Culprit: Lack of Chain Lubrication

Why it matters: The chain needs to be properly lubricated to reduce friction and prevent overheating.

The Fix:

• Step 1: Check the Oil Level: Ensure the oil tank is full.
• Step 2: Check the Oiler Function: Start the saw and hold it over a piece of cardboard. You should see a stream of oil coming from the bar.
• Step 3: Clean the Oiler: If the oiler is not working properly, clean the oiler port and the oil filter.
  • Specification: Use only bar and chain oil specifically designed for chainsaws.
  • Data Point: Proper chain lubrication can extend chain life by up to 50%.

3. The Misfiring Motor: Diagnosing and Resolving Engine Problems

A misfiring engine can be caused by a variety of factors, from a dirty air filter to a faulty ignition coil. Diagnosing the problem can be challenging, but with a systematic approach, you can usually pinpoint the culprit.

The Culprit: Dirty Air Filter

Why it matters: A dirty air filter restricts airflow to the engine, leading to a rich fuel mixture and poor performance.

The Fix:

• Step 1: Inspection: Remove the air filter and inspect it. If it’s dirty, clean it or replace it.
  • Procedure: Remove the air filter cover and carefully remove the air filter.
  • Material Specification: Air filters are typically made of foam or paper.
• Step 2: Cleaning: Clean a foam air filter with warm soapy water. Allow it to dry completely before reinstalling. Replace a paper air filter if it’s heavily soiled.
  • Specification: Clean the air filter after every 25 hours of use, or more frequently in dusty conditions.
  • Practical Tip: I like to keep a spare air filter on hand so I can quickly swap it out when the original gets dirty.

The Culprit: Faulty Ignition Coil

Why it matters: The ignition coil provides the high-voltage spark that ignites the air-fuel mixture. A faulty ignition coil will cause the engine to misfire or not start at all.

The Fix:

• Step 1: Testing: Test the ignition coil with a multimeter.
  • Procedure: Disconnect the spark plug wire from the spark plug. Set the multimeter to measure resistance. Connect the multimeter probes to the ignition coil terminals.
  • Tool Requirement: Multimeter.
  • Specification: Consult the Stihl MS 270 service manual for the correct resistance readings.
  • Technical Limitation: Testing the ignition coil requires specialized equipment and knowledge. If you’re not comfortable with this, take the saw to a qualified technician.
• Step 2: Replacement: If the ignition coil is faulty, replace it.
  • Safety Code: Disconnect the spark plug wire before replacing the ignition coil.

The Culprit: Exhaust Port Clogging

Why it matters: Over time, carbon deposits can build up in the exhaust port, restricting exhaust flow and causing the engine to misfire.

The Fix:

• Step 1: Inspection: Remove the muffler and inspect the exhaust port. Look for carbon buildup.
  • Procedure: Remove the muffler mounting screws and carefully remove the muffler.
  • Tool Requirement: Screwdriver or socket wrench.
• Step 2: Cleaning: Clean the exhaust port with a wire brush or a carbon scraper.
  • Safety Code: Wear safety glasses and gloves when cleaning the exhaust port.
  • Practical Tip: I find that using a small screwdriver to carefully scrape away the carbon deposits works well.

4. The Overheating Engine: Preventing and Addressing Heat-Related Issues

An overheating engine can cause serious damage to your chainsaw. It’s important to understand the causes of overheating and take steps to prevent it.

The Culprit: Insufficient Cooling

Why it matters: The engine relies on air cooling to dissipate heat. Blocked cooling fins or a damaged cooling fan can reduce airflow and cause the engine to overheat.

The Fix:

• Step 1: Inspection: Inspect the cooling fins on the cylinder and the cooling fan. Make sure they are clean and free of debris.
  • Procedure: Remove the air filter cover and inspect the cooling fins. Inspect the cooling fan through the air filter opening.
• Step 2: Cleaning: Clean the cooling fins with a brush or compressed air.
  • Safety Code: Wear safety glasses when using compressed air.

The Culprit: Lean Fuel Mixture

Why it matters: A lean fuel mixture (too much air, not enough fuel) can cause the engine to run hot.

The Fix:

• Step 1: Carburetor Adjustment: Adjust the carburetor to richen the fuel mixture.
  • Procedure: Consult the Stihl MS 270 service manual for instructions on adjusting the carburetor.
  • Technical Limitation: Carburetor adjustment requires specialized knowledge and tools. If you’re not comfortable with this, take the saw to a qualified technician.

The Culprit: Excessive Load

Why it matters: Cutting wood that is too large or too hard can put excessive strain on the engine, causing it to overheat.

The Fix:

• Step 1: Reduce Load: Use a smaller bar and chain for cutting smaller wood. Avoid cutting wood that is too hard or too dense.
  • Specification: The Stihl MS 270 is best suited for cutting wood up to 16 inches in diameter.

5. The Chain Brake Breakdown: Ensuring Safe Operation

The chain brake is a critical safety feature that stops the chain immediately in the event of kickback. It’s essential to ensure that the chain brake is functioning properly.

The Culprit: Damaged Chain Brake Mechanism

Why it matters: A damaged chain brake mechanism can prevent the chain brake from engaging properly, increasing the risk of injury.

The Fix:

• Step 1: Inspection: Inspect the chain brake handle and the chain brake band. Look for signs of damage or wear.
  • Procedure: Manually engage and disengage the chain brake. Check for smooth operation and proper engagement.
• Step 2: Cleaning: Clean the chain brake mechanism with a brush and solvent.
• Step 3: Replacement: If the chain brake mechanism is damaged, replace it.
  • Safety Code: Disconnect the spark plug wire before working on the chain brake.

The Culprit: Improper Adjustment

Why it matters: An improperly adjusted chain brake can be too loose or too tight, affecting its effectiveness.

The Fix:

• Step 1: Adjustment: Adjust the chain brake according to the manufacturer’s instructions.
  • Procedure: Consult the Stihl MS 270 service manual for instructions on adjusting the chain brake.
  • Technical Limitation: Chain brake adjustment requires specialized knowledge and tools. If you’re not comfortable with this, take the saw to a qualified technician.

Beyond the Fixes: Preventative Maintenance is Key

Troubleshooting is essential, but prevention is even better. Here’s a summary of key maintenance tasks I perform regularly to keep my Stihl MS 270 running strong:

• Daily:
  • Check and clean the air filter.
  • Check the chain tension.
  • Check the oil level.
  • Sharpen the chain as needed.
• Weekly:
  • Clean the chainsaw thoroughly.
  • Inspect the spark plug.
  • Clean the cooling fins.
• Monthly:
  • Replace the fuel filter.
  • Inspect the chain brake.
• Annually:
  • Have the carburetor professionally cleaned and adjusted.
  • Replace the spark plug.

A Final Thought: Respect the Power

The Stihl MS 270 is a powerful tool, and like any powerful tool, it demands respect. Always wear appropriate safety gear, including a helmet, eye protection, hearing protection, gloves, and chainsaw chaps. Read and understand the owner’s manual before operating the saw. And never operate the saw when you are tired or under the influence of drugs or alcohol.

Woodworking and logging, for me, are not just hobbies; they are a way of life. They connect me to nature, challenge me physically and mentally, and provide a sense of accomplishment that is hard to find elsewhere. By following these troubleshooting tips and preventative maintenance practices, you can keep your Stihl MS 270 running smoothly and safely for years to come, allowing you to enjoy the rewards of working with wood for as long as I have. Remember, a well-maintained chainsaw is a safe chainsaw, and a safe chainsaw allows you to focus on the joy of the craft. Now get out there and make some sawdust!

Learn more