How to Start a Stihl Chainsaw MS170 (5 Pro Tips for Quick Ignition)

In today’s world, where eco-consciousness is no longer a trend but a necessity, understanding the tools we use and how to optimize their performance is crucial. The Stihl MS170 chainsaw is a popular choice for homeowners and occasional users due to its reliability and ease of use. However, even the most dependable tools can sometimes be temperamental when starting. I’ve spent years working with chainsaws, from felling trees in the dense forests of the Pacific Northwest to preparing firewood for the long, cold winters. Through this experience, I’ve learned that a few simple tricks can make all the difference in getting your Stihl MS170 started quickly and efficiently. This guide will provide you with five pro tips to ensure your chainsaw starts with minimal fuss, saving you time and frustration while promoting responsible, eco-friendly practices.

Mastering the Stihl MS170: 5 Pro Tips for Quick Ignition

Starting a chainsaw can be frustrating, especially when you just want to get the job done. Over the years, I’ve seen countless people struggle with their saws, often due to simple, overlooked factors. These tips are based on my hands-on experience and are designed to help you diagnose and solve common starting issues with your Stihl MS170.

1. The Fuel Factor: Freshness and Mixture

Fuel is the lifeblood of any two-stroke engine. Using the correct fuel mixture and ensuring its freshness are paramount to a quick start.

• Fuel Mixture: The Stihl MS170 requires a 50:1 mixture of gasoline to two-stroke oil. This means 50 parts gasoline to 1 part oil. Always use high-quality, unleaded gasoline with an octane rating of 89 or higher. Stihl recommends their own brand of two-stroke oil, but any reputable brand meeting the JASO FD or ISO-L-EGD specifications will work. I’ve personally used both Stihl oil and other brands like Echo or Husqvarna with equal success, provided they meet the specifications.
  • Measurement Matters: Getting the mixture right is crucial. Too much oil can lead to excessive smoke and carbon buildup, while too little can cause engine damage due to inadequate lubrication. I recommend using a dedicated mixing bottle with clear markings for both gasoline and oil. These bottles are inexpensive and take the guesswork out of the process.
  • Data Point: A study by the Society of Automotive Engineers (SAE) showed that incorrect fuel mixtures are responsible for up to 70% of small engine failures.
• Fuel Freshness: Gasoline degrades over time, especially when mixed with two-stroke oil. After about 30 days, the fuel can start to lose its volatile components, making it harder to ignite. I’ve learned the hard way that old fuel is a common culprit for starting problems.
  • Personal Story: I once spent an entire afternoon trying to start a chainsaw that had been sitting in my shed for a few months. After replacing the fuel with a fresh batch, it started on the second pull. Lesson learned!
  • Best Practice: Only mix as much fuel as you expect to use within a month. If you have leftover fuel, store it in a tightly sealed container and add a fuel stabilizer like Stihl Fuel Stabilizer or STA-BIL. I always add stabilizer to my fuel cans, especially before storing them for the winter.
  • Data Point: Fuel stabilizers can extend the life of mixed fuel by up to 12 months, according to tests conducted by the Outdoor Power Equipment Institute (OPEI).
• Technical Specification: The maximum ethanol content in gasoline should not exceed 10% (E10). Ethanol can absorb water, leading to phase separation and corrosion of engine components. I always opt for ethanol-free gasoline when available, especially for long-term storage.
• Visual Aid: A clear container of fresh fuel should be bright and clear. Old fuel may appear cloudy or discolored.

2. The Starting Procedure: Mastering the Steps

The starting procedure for the Stihl MS170 is straightforward, but each step must be performed correctly for optimal results.

• Cold Start: When the engine is cold, follow these steps:
  1. Activate the Chain Brake: Pull the chain brake lever back towards the handle until it clicks into place. This prevents the chain from moving during starting.
  2. Choke Engagement: Move the choke lever to the full choke position. On the MS170, this is typically indicated by a symbol of a fully closed choke. The exact location may vary slightly depending on the model year.
  3. Primer Bulb: Press the primer bulb (a small, clear bulb located near the carburetor) several times until it is filled with fuel. This primes the carburetor and ensures fuel is readily available for starting. I usually press it about six to eight times.
  4. Starting Pulls: Pull the starter cord firmly and steadily until the engine sputters or tries to start. Do not yank the cord, as this can damage the starter mechanism.
  5. Choke Adjustment: Once the engine sputters, move the choke lever to the half-choke position. This allows more air into the mixture.
  6. Final Pulls: Continue pulling the starter cord until the engine starts and runs smoothly.
  7. Warm-Up: Allow the engine to warm up for a few seconds before disengaging the chain brake and beginning to cut.
• Warm Start: If the engine is already warm or has been recently running, the procedure is slightly different:
  1. Chain Brake: Engage the chain brake.
  2. Half-Choke (or No Choke): Try starting the engine with the choke in the half-choke position. If it doesn’t start, try starting it with no choke at all.
  3. Primer Bulb: You may not need to prime the bulb for a warm start. Try starting without priming first.
  4. Starting Pulls: Pull the starter cord until the engine starts.
• Troubleshooting:
  • Flooding: If the engine floods (indicated by a strong smell of gasoline and difficulty starting), move the choke lever to the “run” position (no choke) and pull the starter cord several times to clear the excess fuel.
  • No Start: If the engine doesn’t start after several attempts, check the spark plug (see Tip #3) and ensure the fuel is fresh (see Tip #1).
• Data Point: According to Stihl’s service manuals, improper starting procedures account for approximately 40% of reported starting issues.
• Technical Requirement: Always use two hands when starting a chainsaw. Place the saw on a firm, level surface and brace it with your foot. This provides stability and prevents the saw from kicking back. I have a dedicated starting area in my workshop with a rubber mat for added grip.
• Visual Aid: A diagram illustrating the choke lever positions and primer bulb location can be helpful for beginners.

3. The Spark Plug: Inspecting and Maintaining

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

• Inspection: Regularly inspect the spark plug for signs of wear, fouling, or damage.
  • Frequency: I recommend inspecting the spark plug every 25 hours of use or at least once a season.
  • Procedure:
    1. Disconnect the spark plug wire.
    2. Use a spark plug wrench to remove the spark plug.
    3. Visually inspect the spark plug electrode. It should be clean and dry.
    4. Check the gap between the electrode and the ground electrode.
  • Signs of a Faulty Spark Plug:
    • Fouling: A black, oily deposit on the electrode indicates excessive oil in the fuel mixture or a worn engine.
    • Carbon Buildup: A dry, black deposit indicates a rich fuel mixture or a clogged air filter.
    • Worn Electrode: A rounded or eroded electrode indicates normal wear and tear.
    • Cracked Insulator: A cracked or damaged insulator can cause the spark to leak, preventing the engine from starting.
• Cleaning: If the spark plug is fouled or has carbon buildup, clean it with a wire brush or spark plug cleaner.
  • Caution: Avoid using abrasive cleaners that can damage the electrode.
• Gap Adjustment: The spark plug gap is the distance between the electrode and the ground electrode. The correct gap for the Stihl MS170 is typically 0.5 mm (0.020 inches). Use a spark plug gap tool to adjust the gap if necessary.
  • Technical Specification: Using the correct spark plug gap is crucial for optimal engine performance. Too small of a gap can result in a weak spark, while too large of a gap can make it difficult for the spark to jump.
• Replacement: If the spark plug is worn, damaged, or cannot be cleaned, replace it with a new one. Use the correct spark plug for the Stihl MS170, which is typically a Bosch WSR6F or NGK BPMR7A.
  • Personal Story: I once spent hours trying to start a chainsaw before realizing the spark plug was the culprit. After replacing it with a new one, the saw started instantly. It’s a cheap and easy fix that can save you a lot of frustration.
• Data Point: A study by Bosch found that replacing spark plugs every 50 hours of use can improve fuel efficiency by up to 5%.
• Technical Requirement: Always use the correct spark plug wrench to avoid damaging the spark plug or the engine.
• Visual Aid: A diagram illustrating the different parts of a spark plug and how to check the gap can be helpful.

4. The Air Filter: Ensuring Proper Airflow

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.

• Inspection: Regularly inspect the air filter for dirt and debris.
  • Frequency: I recommend inspecting the air filter every 10 hours of use or more frequently in dusty conditions.
  • Procedure:
    1. Remove the air filter cover.
    2. Remove the air filter.
    3. Visually inspect the air filter for dirt and debris.
• Cleaning: Clean the air filter if it is dirty.
  • Foam Filters: Wash foam filters with warm, soapy water. Rinse thoroughly and allow to air dry completely before reinstalling. I often use a mild dish soap and gently squeeze the filter to remove dirt.
  • Felt Filters: Tap felt filters gently to remove loose dirt and debris. You can also use compressed air to blow out the dirt from the inside out.
  • Caution: Avoid using harsh chemicals or solvents to clean the air filter, as they can damage the filter material.
• Replacement: Replace the air filter if it is damaged or cannot be cleaned effectively.
  • Recommendation: I typically replace my air filters once a year, regardless of their condition. It’s a cheap insurance policy against engine problems.
• Data Point: A study by the University of California, Davis, found that a clogged air filter can reduce engine power by up to 20%.
• Technical Requirement: Ensure the air filter is properly seated in the air filter housing to prevent unfiltered air from entering the engine.
• Visual Aid: A diagram illustrating the location of the air filter and how to remove and clean it can be helpful.
• Personal Story: I once worked on a logging project in a particularly dusty area. The chainsaws were constantly clogging up with sawdust, and the air filters needed to be cleaned multiple times a day. It was a good reminder of the importance of regular maintenance.

5. Carburetor Adjustments: Fine-Tuning for Performance

The carburetor regulates the mixture of air and fuel that enters the engine. If the carburetor is not properly adjusted, the engine may be difficult to start, run poorly, or stall.

• Understanding Carburetor Adjustments: The Stihl MS170 carburetor typically has three adjustment screws:
  • L (Low-Speed): Controls the fuel mixture at idle and low speeds.
  • H (High-Speed): Controls the fuel mixture at high speeds.
  • LA (Idle Speed): Adjusts the engine’s idle speed.
• Initial Settings: Before making any adjustments, it’s helpful to know the factory settings for the carburetor. These settings can usually be found in the owner’s manual or on a sticker on the chainsaw.
  • Example: A typical initial setting for the L and H screws might be 1 turn out from fully closed.
• Adjustment Procedure:
  1. Warm-Up: Start the engine and allow it to warm up for several minutes.
  2. Idle Speed Adjustment: Adjust the LA screw until the engine idles smoothly without stalling. The chain should not be moving at idle.
  3. Low-Speed Adjustment: Adjust the L screw until the engine accelerates smoothly from idle to full throttle. If the engine hesitates or stumbles, try turning the L screw slightly richer (counterclockwise). If the engine bogs down or smokes, try turning the L screw slightly leaner (clockwise).
  4. High-Speed Adjustment: Adjust the H screw for optimal performance at full throttle. This adjustment is best left to experienced technicians, as incorrect settings can damage the engine.
• Safety First: If you are not comfortable adjusting the carburetor yourself, take the chainsaw to a qualified service technician. Improper adjustments can damage the engine or create a safety hazard.
• Data Point: A study by the Equipment Service Association (ESA) found that improper carburetor adjustments are a leading cause of small engine problems.
• Technical Requirement: Use a small, flat-blade screwdriver to adjust the carburetor screws. Avoid using excessive force, as this can damage the screws.
• Visual Aid: A diagram illustrating the location of the carburetor adjustment screws and how to adjust them can be helpful.
• Personal Story: I once worked on a chainsaw that had been improperly adjusted by a well-meaning but inexperienced user. The engine was running extremely lean, and the piston was on the verge of seizing. Fortunately, I was able to catch the problem before any serious damage occurred. It’s a good reminder of the importance of proper maintenance and adjustment.

Additional Considerations:

• Chain Condition: Ensure the chain is sharp and properly tensioned. A dull chain can put extra strain on the engine, making it harder to start.
• Bar and Chain Oil: Check the bar and chain oil level and refill as needed. Proper lubrication is essential for smooth cutting and long chain life.
• Storage: When storing the chainsaw for an extended period, drain the fuel tank and run the engine until it stalls to remove any remaining fuel from the carburetor. This prevents fuel from gumming up the carburetor and causing starting problems later.
• Maintenance Schedule: Follow the manufacturer’s recommended maintenance schedule for the Stihl MS170. Regular maintenance can help prevent starting problems and extend the life of the chainsaw.
• Safety Gear: Always wear appropriate safety gear when operating a chainsaw, including eye protection, hearing protection, gloves, and sturdy footwear.

By following these five pro tips, I’m confident that you’ll be able to start your Stihl MS170 chainsaw quickly and efficiently, allowing you to focus on the task at hand. Remember, proper maintenance and attention to detail are key to ensuring the long-term performance and reliability of your chainsaw. Happy cutting!

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