Stihl Chainsaw MS170 Carburetor Upgrade (Boost Power & Efficiency)
Ever felt your Stihl MS170 chainsaw was a bit…anemic? Like it was holding back on you, especially when tackling tougher wood? I know I have. And if you’re nodding along, you’ve probably wondered about a carburetor upgrade. So, can a simple carburetor swap really transform your trusty MS170 into a wood-devouring beast? Let’s dive deep into the world of Stihl MS170 carburetor upgrades, exploring the potential for boosted power and efficiency, the pitfalls to avoid, and everything in between.
The Quest for More Power: Why Upgrade Your MS170 Carburetor?
The Stihl MS170 is a fantastic little chainsaw. It’s lightweight, easy to handle, and perfect for small jobs around the yard, like trimming branches or cutting small diameter firewood. But let’s be honest, it’s not exactly a powerhouse. The stock carburetor is designed for fuel efficiency and ease of use, which often means sacrificing some performance.
Think of it like this: your MS170 is a runner, and the stock carburetor is like a restrictive breathing mask. It allows you to run, but not at your full potential. An upgraded carburetor, in theory, removes that mask, allowing the engine to breathe more freely and generate more power.
My Own “Anemic Chainsaw” Story
I remember one particularly frustrating afternoon trying to buck up some seasoned oak rounds with my MS170. It was bogging down constantly, and progress was painfully slow. I was spending more time wrestling with the saw than actually cutting wood. That’s when the idea of a carburetor upgrade first popped into my head. I thought, “There has to be a way to get more out of this thing!”
The Promise of Increased Performance
The allure of a carburetor upgrade is simple: more power and better efficiency. A well-chosen and properly tuned aftermarket carburetor can offer several benefits:
- Increased Horsepower: A larger venturi and improved fuel metering can allow the engine to take in more air and fuel, resulting in a more powerful combustion.
- Improved Throttle Response: Upgraded carburetors often provide crisper throttle response, making the saw feel more responsive and agile.
- Easier Starting: Some upgrades feature improved choke mechanisms or fuel priming systems, making cold starts easier.
- Enhanced Fuel Efficiency: Counterintuitively, a properly tuned upgraded carburetor can sometimes improve fuel efficiency by optimizing the air-fuel mixture.
- Better High-Altitude Performance: Stock carburetors can struggle at higher altitudes due to the thinner air. Some aftermarket options are designed to compensate for this.
Decoding the Carburetor: How It All Works
Before we get into specific upgrades, let’s take a quick look at how a carburetor actually works. Understanding the fundamentals will help you make a more informed decision about whether or not an upgrade is right for you.
The carburetor’s primary function is to mix air and fuel in the correct proportions to create a combustible mixture that the engine can burn. It does this using a venturi, a narrow passage that creates a low-pressure area as air flows through it. This low pressure draws fuel from the fuel bowl into the airstream, where it atomizes and mixes with the air.
The carburetor also controls the amount of air and fuel that enters the engine, which in turn controls the engine’s speed and power. This is achieved through the throttle valve, which is connected to the throttle trigger. When you pull the trigger, the throttle valve opens, allowing more air and fuel to flow into the engine.
There are generally two main routes you can take:
- Direct Replacement Carburetors: These are aftermarket carburetors specifically designed to replace the stock carburetor on the MS170. They typically offer improved performance and are relatively easy to install.
- Modified or Tuned Stock Carburetors: This involves modifying the existing carburetor by drilling out jets, adjusting the throttle plate, or making other changes to improve its performance. This option requires more technical expertise and is generally not recommended for beginners.
A Closer Look at Direct Replacement Carburetors
Direct replacement carburetors are the most popular option for upgrading the MS170. They offer a good balance of performance, ease of installation, and affordability. Here are some of the factors to consider when choosing a direct replacement carburetor:
- Brand Reputation: Stick with reputable brands that are known for producing high-quality carburetors. Some popular brands include Walbro, Zama, and Tillotson.
- Venturi Size: A larger venturi will generally provide more power, but it can also make the saw more difficult to start and tune.
- Adjustability: Look for a carburetor that has adjustable high and low-speed jets, allowing you to fine-tune the air-fuel mixture for optimal performance.
- Construction Quality: Make sure the carburetor is made from durable materials that can withstand the rigors of chainsaw use.
The Allure (and Peril) of Modifying Your Stock Carburetor
While modifying your stock carburetor might seem like a cost-effective option, it’s generally not recommended unless you have a thorough understanding of carburetor mechanics and tuning. Making even small changes to the carburetor can have a significant impact on its performance, and it’s easy to damage the carburetor beyond repair.
I’ve personally seen (and unfortunately, done) more harm than good trying to “tweak” carburetors without the proper knowledge. One time, I tried drilling out the main jet on an old brush cutter carburetor, thinking it would give it more power. Instead, I ended up with a saw that ran incredibly rich, smoked like a chimney, and barely idled. Lesson learned: sometimes, it’s better to leave things to the professionals (or just buy a new carburetor!).
Installation: Getting Your Hands Dirty
Installing a direct replacement carburetor on your Stihl MS170 is a relatively straightforward process that can be completed in about an hour with basic tools. However, it’s important to follow the instructions carefully and take your time to avoid damaging the carburetor or the saw.
Here’s a general overview of the installation process:
- Gather Your Tools: You’ll need a screwdriver, a wrench, a pair of pliers, and potentially some carb cleaner.
- Remove the Air Filter Cover: This is usually held in place by a few screws or clips.
- Remove the Air Filter: Carefully remove the air filter and set it aside.
- Disconnect the Fuel Line and Throttle Linkage: Use pliers to disconnect the fuel line from the carburetor and carefully detach the throttle linkage.
- Remove the Old Carburetor: Unscrew the bolts or screws that hold the carburetor in place and carefully remove it from the saw.
- Install the New Carburetor: Align the new carburetor with the mounting holes and secure it with the bolts or screws.
- Reconnect the Fuel Line and Throttle Linkage: Reattach the fuel line and throttle linkage to the new carburetor.
- Reinstall the Air Filter and Air Filter Cover: Put the air filter back in place and reinstall the air filter cover.
Important Safety Tip: Always disconnect the spark plug wire before working on the carburetor to prevent accidental starting.
Tuning for Peak Performance: The Art of the Air-Fuel Mixture
Once you’ve installed the new carburetor, the next step is to tune it for optimal performance. This involves adjusting the high and low-speed jets to achieve the correct air-fuel mixture.
- The High-Speed Jet (H): Controls the air-fuel mixture at high speeds.
- The Low-Speed Jet (L): Controls the air-fuel mixture at idle and low speeds.
Tuning the carburetor is a delicate balancing act. If the air-fuel mixture is too lean (too much air, not enough fuel), the engine will run hot and may be damaged. If the mixture is too rich (too much fuel, not enough air), the engine will run sluggishly and may foul the spark plug.
Here’s a general guideline for tuning the carburetor:
- Start with the Factory Settings: Most aftermarket carburetors come with factory settings that are a good starting point.
- Adjust the Low-Speed Jet (L): Turn the low-speed jet in or out until the engine idles smoothly and responds quickly to the throttle.
- Adjust the High-Speed Jet (H): Make a test cut in a piece of wood. If the engine bogs down or smokes excessively, turn the high-speed jet out slightly. If the engine runs lean or hesitates, turn the high-speed jet in slightly.
- Repeat the Process: Continue making small adjustments to the high and low-speed jets until the engine runs smoothly and powerfully throughout the entire RPM range.
Tools of the Trade: A small tachometer can be helpful for setting the idle speed and ensuring that the engine is not over-revving.
The Downside: Potential Drawbacks of Upgrading
While a carburetor upgrade can offer significant performance benefits, it’s important to be aware of the potential drawbacks:
- Increased Fuel Consumption: A larger venturi and richer fuel mixture can lead to increased fuel consumption.
- Difficult Starting: Some upgraded carburetors can be more difficult to start, especially in cold weather.
- Increased Noise: A more powerful engine can also be a louder engine.
- Potential for Engine Damage: If the carburetor is not properly tuned, it can lead to engine damage.
- Warranty Issues: Installing an aftermarket carburetor may void the warranty on your chainsaw.
Wood Species and Carburetor Performance: A Tangled Web
The type of wood you’re cutting can also affect carburetor performance. Denser, harder woods like oak and maple require more power to cut than softer woods like pine and cedar. This means that you may need to fine-tune the carburetor differently depending on the type of wood you’re cutting.
For example, when cutting hardwoods, you may need to richen the high-speed jet slightly to provide more power and prevent the engine from bogging down. Conversely, when cutting softwoods, you may need to lean out the high-speed jet slightly to improve fuel efficiency.
A Case Study: Oak vs. Pine
I once spent a week cutting both oak and pine firewood. With the stock MS170 carburetor, the difference was noticeable, but manageable. However, after upgrading to an aftermarket carburetor, the difference became much more pronounced. The saw was an absolute beast in pine, ripping through logs with ease. But in oak, it required more careful tuning and a slightly richer fuel mixture to prevent bogging down.
Data Points on Wood Density:
- Oak (Red): Average density of 0.75 g/cm³
- Maple (Hard): Average density of 0.70 g/cm³
- Pine (Eastern White): Average density of 0.35 g/cm³
- Cedar (Western Red): Average density of 0.32 g/cm³
These differences in density directly impact the amount of power required to cut through the wood, and therefore, the optimal carburetor tuning.
Safety First: Protecting Yourself and Your Saw
Working with chainsaws is inherently dangerous, and it’s crucial to prioritize safety at all times. Here are some essential safety tips to keep in mind:
- Wear Appropriate Safety Gear: Always wear safety glasses, hearing protection, gloves, and chainsaw chaps.
- Inspect Your Chainsaw Before Each Use: Check the chain tension, oil level, and overall condition of the saw.
- Use Proper Cutting Techniques: Avoid kickback by keeping the nose of the saw away from obstructions.
- Maintain a Safe Working Distance: Keep bystanders at least 20 feet away from the cutting area.
- Never Operate a Chainsaw When Fatigued or Under the Influence of Drugs or Alcohol.
Safety Data: According to the Consumer Product Safety Commission (CPSC), chainsaws cause tens of thousands of injuries each year in the United States alone. Wearing proper safety gear can significantly reduce the risk of injury.
The Verdict: Is a Carburetor Upgrade Worth It?
So, is a carburetor upgrade for your Stihl MS170 worth the investment? The answer, as with most things, depends on your individual needs and expectations.
Here’s a quick summary of the pros and cons:
Pros:
- Increased Power
- Improved Throttle Response
- Easier Starting (Potentially)
- Enhanced Fuel Efficiency (Potentially)
- Better High-Altitude Performance (Potentially)
Cons:
- Increased Fuel Consumption (Potentially)
- Difficult Starting (Potentially)
- Increased Noise (Potentially)
- Potential for Engine Damage
- Warranty Issues
If you’re looking for a noticeable boost in power and are willing to spend the time and effort to properly install and tune the carburetor, then an upgrade may be a good option for you. However, if you’re primarily using your MS170 for light-duty tasks and are concerned about fuel consumption or warranty issues, then you may be better off sticking with the stock carburetor.
Beyond the Carburetor: Other Ways to Boost Performance
Before you jump headfirst into a carburetor upgrade, it’s worth considering other ways to improve the performance of your Stihl MS170.
- Sharpen Your Chain: A sharp chain is essential for efficient cutting. Dull chains require more power and can lead to increased wear and tear on the saw.
- Use the Right Chain: Different types of chains are designed for different types of wood. Using the correct chain can significantly improve cutting performance.
- Maintain Proper Chain Tension: A properly tensioned chain will cut more efficiently and reduce the risk of kickback.
- Clean Your Air Filter: A dirty air filter can restrict airflow and reduce engine performance.
- Use High-Quality Fuel and Oil: Using high-quality fuel and oil can help keep your engine running smoothly and prevent premature wear.
The Future of Chainsaw Technology: What’s on the Horizon?
The world of chainsaw technology is constantly evolving, with manufacturers developing new and innovative ways to improve performance, efficiency, and safety.
- Electronic Fuel Injection (EFI): EFI systems offer more precise fuel metering than carburetors, resulting in improved fuel efficiency and performance. Some newer chainsaws are already equipped with EFI systems.
- Battery-Powered Chainsaws: Battery-powered chainsaws are becoming increasingly popular, offering a quieter and more environmentally friendly alternative to gasoline-powered saws.
- Smart Chainsaws: Some manufacturers are developing “smart” chainsaws that can monitor engine performance, provide diagnostic information, and even adjust settings automatically.
Final Thoughts: A Woodcutter’s Perspective
Upgrading the carburetor on your Stihl MS170 can be a rewarding experience, transforming a capable little saw into a more powerful and efficient cutting machine. However, it’s important to weigh the pros and cons carefully and to approach the project with a healthy dose of caution and respect.
Remember, a chainsaw is a powerful tool, and safety should always be your top priority. By following the tips and guidelines outlined in this article, you can safely and effectively upgrade your MS170 carburetor and enjoy the benefits of increased power and performance.
And who knows, maybe you’ll even find yourself looking for excuses to cut more firewood! I know I did.
