The Complete Overview of How to Start a Stihl MS 170 Chainsaw
The Stihl MS 170’s starting sequence is a study in controlled chaos: a precise dance between manual and automatic systems where one misstep can stall the engine before it ever revs. Unlike smaller saws that rely on choke settings alone, the MS 170 integrates a decompression valve and a semi-automatic choke that adjusts based on engine temperature. This dual-system approach ensures reliability in varying climates, but it also means operators must account for both cold and warm starts—each requiring a distinct approach. At its heart, the MS 170’s starting process hinges on three interlocking components: the carburetor’s fuel-air mixture, the ignition coil’s spark generation, and the flywheel’s momentum buildup. The saw’s pull-start system is designed to minimize effort while maximizing efficiency; the recoil starter’s spring tension is calibrated to deliver consistent torque, reducing the risk of broken cords or wasted energy. However, this system only functions optimally when maintained—dirty spark plugs or a clogged air filter can turn a 3-second start into a 3-minute struggle.Historical Background and Evolution
The MS 170 traces its lineage back to Stihl’s 1926 founding, when Andreas Stihl invented the first portable chainsaw to clear brush for his family’s farm. By the 1970s, the company had refined its two-stroke engines to balance power and portability, and the MS 170—introduced in the 1980s—became a benchmark for professional-grade saws. Its design was shaped by feedback from loggers who needed a tool that could handle daily abuse without frequent overhauls. The MS 170’s enduring popularity stems from its ability to start reliably in temperatures ranging from -10°C to 40°C, a feat achieved through progressive choke mechanisms and optimized fuel delivery. What sets the MS 170 apart from earlier models is its integration of a semi-automatic choke, a feature that debuted in the late 1990s. This innovation eliminated the need for manual choke adjustments during warm-up, reducing operator error and extending engine life. The saw’s carburetor, too, evolved to handle modern fuel blends without requiring constant tuning—a critical advancement for professionals who can’t afford downtime. Today, the MS 170 remains a staple in forestry and construction, its starting procedure a testament to decades of refinement.Core Mechanisms: How It Works
Under the hood, the MS 170’s starting sequence unfolds in three phases: priming, ignition, and throttle engagement. When the engine is cold, the semi-automatic choke enriches the fuel mixture by restricting air intake, creating a vapor-rich blend that’s easier to ignite. As the engine warms, the choke gradually opens, transitioning to a leaner mixture for optimal power. This process is managed by a thermostat-like sensor that modulates the choke plate based on exhaust temperature, ensuring smooth transitions between cold and warm starts. The ignition system plays an equally critical role. The MS 170 uses a CDI (Capacitor Discharge Ignition) module, which stores electrical energy and releases it as a high-voltage spark when the flywheel’s magnet passes the coil. This system is more reliable than traditional points-based ignition, as it eliminates wear-prone components. However, its effectiveness depends on proper spark plug selection (NGK DR8YA or equivalent) and gap setting (0.020–0.025 inches). A weak spark—often caused by fouled plugs or low compression—can prevent the engine from firing, even with correct choke settings.Key Benefits and Crucial Impact
Few tools in the arborist’s arsenal combine precision and power as effectively as the Stihl MS 170. Its ability to start consistently under demanding conditions—whether it’s a subzero morning in the Rockies or a humid afternoon in the Southeast—makes it indispensable for professionals who can’t afford delays. The saw’s engineering isn’t just about brute force; it’s about efficiency. A properly started MS 170 delivers 2.6 horsepower to the chain with minimal vibration, reducing operator fatigue during long shifts. This balance of performance and ergonomics explains why it remains the gold standard for contractors and homeowners alike. The MS 170’s starting procedure also reflects Stihl’s commitment to sustainability. Its two-stroke engine, while powerful, is designed to run cleanly when maintained correctly. Using the proper fuel mix (Stihl’s recommended 50:1 ratio for modern blends) ensures complete combustion, minimizing emissions and extending engine life. This attention to detail extends to the saw’s air filtration system, which is engineered to trap debris while allowing optimal airflow—a critical factor in preventing premature wear.“A chainsaw is only as good as its first pull. The MS 170’s starting sequence isn’t just about getting it running; it’s about preserving its longevity. Skimp on the preparation, and you’ll pay for it in repairs.” — **Mark R., Certified Stihl Technician**
Major Advantages
- Cold-Weather Reliability: The semi-automatic choke and decompression valve ensure starts in temperatures as low as -10°C without preheating, a feature critical for winter operations.
- Fuel Efficiency: The carburetor’s precise fuel-air ratio minimizes waste, reducing long-term costs compared to saws that require frequent tuning.
- Low Maintenance: Stihl’s engineered components, like the self-adjusting clutch and durable piston rings, reduce the need for frequent overhauls.
- Ergonomic Design: The saw’s balanced weight (11.5 lbs) and vibration-dampening system make it comfortable for extended use, reducing operator fatigue.
- Versatility: With a 14-inch bar and chain, the MS 170 handles everything from limb pruning to small tree felling, making it a one-tool solution for many tasks.
Comparative Analysis
| Stihl MS 170 | Husqvarna 440 |
|---|---|
| Semi-automatic choke for effortless cold starts | Manual choke requiring precise adjustment |
| CDI ignition for consistent spark in all conditions | Points-based ignition (older models) prone to wear |
| Decompression valve reduces pull-start effort | No decompression valve; requires stronger pulls |
| 1.5HP with 2.6HP at the chain; optimized for efficiency | 1.7HP with 3.1HP at the chain; higher torque but less fuel-efficient |
Future Trends and Innovations
As battery technology advances, the next generation of chainsaws may render the MS 170’s two-stroke engine obsolete—but for now, its starting procedure remains a benchmark for reliability. Stihl has already introduced hybrid models (like the MSA 200) that combine electric motors with two-stroke assistance, hinting at a future where starting techniques evolve to include smart diagnostics and adaptive fuel delivery. However, the MS 170’s manual starting process is unlikely to disappear entirely; its simplicity and durability still outperform many electronic alternatives in rugged environments. One emerging trend is the integration of IoT sensors into chainsaws, which could monitor fuel levels, oil viscosity, and even ambient temperature to optimize starting conditions automatically. While this technology is years away from consumer models, it underscores the industry’s shift toward predictive maintenance—where a saw might alert its operator to pre-start adjustments before a problem arises. Until then, the MS 170’s starting procedure remains a masterclass in mechanical efficiency, proving that sometimes, the best innovations are timeless.
Conclusion
The Stihl MS 170’s starting process is more than a sequence of steps; it’s a reflection of its engineering philosophy. Every pull of the cord is an opportunity to reinforce the saw’s longevity, and every adjustment—from choke position to throttle timing—matters. For professionals, this means fewer interruptions and lower maintenance costs. For enthusiasts, it’s a chance to connect with a tool built for decades of service. The MS 170 doesn’t demand blind obedience; it rewards attention to detail, offering rewards in the form of consistent power and durability. As with any precision instrument, the key to success lies in preparation. A well-maintained MS 170 starts reliably, runs smoothly, and lasts for years—provided its operator respects its mechanics. Whether you’re tackling a morning’s worth of limbs or preparing for a winter storm cleanup, understanding how to start a Stihl MS 170 isn’t just about ignition; it’s about mastering a tool that’s been perfected over generations.Comprehensive FAQs
Q: Why does my Stihl MS 170 backfire when starting?
The most common causes are an incorrect air-fuel mixture (too much fuel or too little air), a fouled spark plug, or a clogged exhaust port. Start by checking the fuel ratio (50:1 for modern blends) and ensuring the spark plug gap is 0.020–0.025 inches. If the issue persists, inspect the exhaust for carbon buildup or blockages.
Q: Can I use regular gasoline in my MS 170?
No. The MS 170 requires a 50:1 oil-to-fuel ratio with Stihl-branded or high-quality two-stroke oil. Regular gasoline lacks the necessary lubrication, leading to rapid engine wear. Always use fresh fuel mixed within 30 days to prevent varnish buildup.
Q: How often should I clean the air filter on my MS 170?
Stihl recommends cleaning the air filter every 10 hours of operation or more frequently in dusty conditions. Use compressed air to remove debris and replace the filter if it’s torn or saturated with oil. A clogged filter restricts airflow, causing the engine to run rich and increasing wear.
Q: What’s the correct chain brake engagement procedure?
Before starting, ensure the chain brake is engaged (chain stopped) to prevent accidental movement. After starting, the brake should disengage automatically when you squeeze the throttle. If it doesn’t, check the brake cable tension or the brake mechanism for obstructions.
Q: My MS 170 won’t stay running after starting. What should I do?
This is often caused by a dirty carburetor, weak spark, or incorrect fuel mixture. Try these steps: 1) Check the spark plug for fouling or damage. 2) Verify the fuel mix and ensure the tank isn’t empty. 3) Inspect the carburetor jets for clogs (use carburetor cleaner). If the issue persists, the engine may need a compression test.
Q: Is there a difference between starting the MS 170 in cold vs. warm conditions?
Yes. In cold weather, use the choke setting (usually marked "C") and pull firmly until the engine catches, then release the choke gradually. In warm conditions, start with the choke in the "H" (hot) position or off entirely. The semi-automatic choke adjusts automatically once the engine reaches operating temperature.
Q: How do I adjust the throttle stop screw if the MS 170 runs too fast?
The throttle stop screw (located on the carburetor) controls the maximum RPM. Turn it clockwise to reduce speed and counterclockwise to increase it. Make small adjustments (1/8 turn) and test the engine between changes. Never adjust the screw with the engine running.
Q: Can I use a different brand of spark plug in my MS 170?
Stihl recommends NGK DR8YA or equivalent plugs (e.g., Bosch WSR6A). Using the wrong plug can cause misfires or engine damage. Always replace plugs with new ones and gap them to 0.020–0.025 inches before installation.
Q: What’s the best way to store my MS 170 between uses?
1) Run the engine until it cools slightly to prevent moisture buildup. 2) Drain the fuel tank and run the engine dry to avoid gumming. 3) Store the saw in a dry place with the air filter removed or covered. For long-term storage, use a fuel stabilizer if keeping fuel in the tank.
Q: Why does my MS 170 smoke excessively when starting?
Excessive smoke usually indicates a rich fuel mixture, often caused by a clogged air filter, dirty carburetor, or incorrect fuel ratio. Clean or replace the air filter, check the carburetor jets, and verify the oil-to-fuel ratio. If the problem continues, the piston rings or cylinder may be worn.
Q: How do I know if my MS 170’s carburetor needs cleaning?
Signs include rough idling, difficulty starting, excessive fuel consumption, or black smoke. If you’ve ruled out spark plug and air filter issues, disassemble the carburetor and clean the jets, float chamber, and passages with carburetor cleaner. Avoid over-tightening screws during reassembly.
