Stihl MS170 Upgrades (5 Expert Muffler Mods)

Let’s face it, the Stihl MS170 is a workhorse. It’s the trusty pickup truck of the chainsaw world – reliable, affordable, and gets the job done. And for many of us, that means one thing: unleashing a little more power from that little engine. That’s where muffler modifications come in.

Over the years, I’ve spent countless hours in the woods, felling trees, bucking logs, and splitting firewood. I’ve used everything from high-end professional saws to entry-level models like the MS170. And while the MS170 might not have the raw power of a larger saw, it’s incredibly versatile and easy to handle, making it a favorite for smaller jobs and beginners. But I always felt it was a bit…restricted.

The stock muffler on the MS170 is designed to keep noise levels down and meet emissions standards. And while that’s important, it also chokes the engine’s performance. By modifying the muffler, we can improve exhaust flow, allowing the engine to breathe easier and produce more power.

Now, I’m not talking about turning your MS170 into a fire-breathing monster. We’re aiming for subtle but noticeable improvements that can make your saw more efficient and enjoyable to use. Think of it as giving your trusty pickup truck a performance exhaust system – a little more pep in its step without sacrificing reliability.

In this article, I’ll be sharing five expert muffler modifications for the Stihl MS170, based on my experience and research. I’ll walk you through each modification step-by-step, explaining the benefits, potential drawbacks, and tools you’ll need. I’ll also delve into the theory behind why these modifications work, so you can understand the principles involved and apply them to other small engine projects. I’ll also cover the potential pitfalls, like running lean, and how to avoid them.

Remember, safety is paramount. Always wear appropriate safety gear, including eye protection, hearing protection, and gloves, when working on your chainsaw. And if you’re not comfortable performing these modifications yourself, it’s always best to consult with a qualified mechanic.

Understanding the Basics: Why Muffler Mods Work

Before we dive into the specific modifications, let’s take a moment to understand the theory behind why they work. The internal combustion engine in your MS170 works by drawing in air and fuel, compressing it, igniting it, and then expelling the exhaust gases. The easier it is for the engine to expel those exhaust gases, the more efficiently it can draw in fresh air and fuel for the next combustion cycle.

The stock muffler on the MS170 is designed with a series of baffles and chambers that restrict exhaust flow. This is done to reduce noise and meet emissions standards. However, this restriction also creates backpressure, which hinders the engine’s ability to breathe freely.

By modifying the muffler, we can reduce backpressure and improve exhaust flow. This allows the engine to run cooler, produce more power, and respond more quickly to changes in throttle. It’s like removing a clogged air filter – the engine can breathe easier and perform better.

Data Point: Studies have shown that muffler modifications can increase chainsaw power output by up to 10-15%, depending on the specific modification and the engine’s condition.

Safety First: Essential Precautions

Before you even think about picking up a tool, let’s talk about safety. Chainsaws are powerful and potentially dangerous machines, and it’s crucial to take the necessary precautions to protect yourself.

• Eye Protection: Always wear safety glasses or a face shield to protect your eyes from flying debris.
• Hearing Protection: Chainsaws are loud, and prolonged exposure to high noise levels can damage your hearing. Wear earplugs or earmuffs to protect your ears.
• Gloves: Wear work gloves to protect your hands from cuts and abrasions.
• Proper Clothing: Wear sturdy clothing that covers your arms and legs. Avoid loose clothing that could get caught in the saw.
• Work Area: Work in a well-ventilated area, away from flammable materials.
• Disconnect Spark Plug: Before working on the muffler, disconnect the spark plug wire to prevent accidental starting.
• Cool Down: Allow the engine to cool down completely before working on the muffler.

Tools You’ll Need

Here’s a list of the tools you’ll need for most of these muffler modifications:

• Screwdrivers: A set of screwdrivers, including Phillips head and flathead, in various sizes.
• Socket Set: A socket set with metric sockets to remove the muffler.
• Drill: A drill with various drill bits, including a step drill bit.
• Metal File: A metal file to smooth out any sharp edges.
• Dremel Tool: A Dremel tool with cutting and grinding attachments (optional, but very helpful).
• Welder: A welder for more advanced modifications (optional).
• Safety Glasses: Always wear safety glasses when working with power tools.
• Gloves: Wear work gloves to protect your hands.
• Marker: A marker to mark cutting lines.
• Measuring Tape: A measuring tape for accurate measurements.

Stihl MS170 Muffler Mods: 5 Expert Options

Now, let’s get to the good stuff – the muffler modifications themselves. I’ve broken them down into five different options, ranging from simple and easy to more complex and advanced. Choose the modification that best suits your skills and comfort level.

1. The Simple Screen Removal: Easiest Performance Boost

This is the easiest and most basic modification you can do to your MS170 muffler. It involves simply removing the spark arrestor screen from the muffler.

Why it works: The spark arrestor screen is designed to prevent sparks from escaping the muffler, which can be a fire hazard in dry conditions. However, it also restricts exhaust flow, reducing power. Removing the screen allows the engine to breathe easier, resulting in a small but noticeable increase in power.

How to do it:

1. Remove the muffler from the chainsaw.
2. Locate the spark arrestor screen. It’s usually held in place by a small retaining clip or screw.
3. Remove the retaining clip or screw.
4. Carefully remove the spark arrestor screen. You may need to use a small screwdriver or pliers to pry it out.
5. Reinstall the muffler.

Pros:

• Very easy to do.
• Requires minimal tools.
• Provides a small but noticeable increase in power.
• Free!

Cons:

• Increases the risk of starting a fire in dry conditions.
• May not be legal in some areas.
• The performance gain is minimal compared to other modifications.

My Experience: I’ve done this modification on several MS170s, and while the power increase isn’t dramatic, it’s definitely noticeable. The saw feels a bit more responsive and doesn’t bog down as easily when cutting through thicker wood. However, I always make sure to check local regulations and fire conditions before removing the spark arrestor screen.

Wood Species Consideration: This mod is particularly helpful when cutting denser hardwoods like oak or maple, where the saw tends to bog down more easily.

2. The Additional Outlet: A Step Up in Flow

This modification involves drilling an additional outlet in the muffler to improve exhaust flow.

Why it works: By adding an additional outlet, you’re effectively increasing the muffler’s surface area, allowing more exhaust gases to escape. This reduces backpressure and allows the engine to breathe easier.

How to do it:

1. Remove the muffler from the chainsaw.
2. Choose a location for the additional outlet. A good spot is usually on the opposite side of the existing outlet, or on the side of the muffler.
3. Using a drill with a step drill bit, carefully drill a hole in the muffler. Start with a small pilot hole and gradually increase the size of the hole until it’s about the same size as the existing outlet.
4. Use a metal file or Dremel tool to smooth out any sharp edges around the new outlet.
5. Reinstall the muffler.

Pros:

• Relatively easy to do.
• Provides a noticeable increase in power.
• Doesn’t significantly increase noise levels.

Cons:

• Requires drilling into the muffler.
• May require some filing or grinding to smooth out the edges.
• Can potentially weaken the muffler if not done carefully.

My Experience: I’ve found that this modification provides a good balance between performance and ease of installation. It’s a noticeable improvement over the stock muffler, without requiring any specialized tools or skills. I recommend using a step drill bit to avoid accidentally drilling too large of a hole.

Safety Considerations: Wear safety glasses and gloves when drilling into the muffler. Be careful not to damage any internal components of the muffler.

3. The Deflector Plate Modification: Directing the Flow

This modification involves modifying the deflector plate inside the muffler to improve exhaust flow.

Why it works: The deflector plate is designed to direct exhaust gases through the muffler’s chambers. By modifying the plate, you can reduce turbulence and improve the flow of exhaust gases.

How to do it:

1. Remove the muffler from the chainsaw.
2. Locate the deflector plate inside the muffler. It’s usually a small metal plate with several holes or slots.
3. Using a Dremel tool with a cutting attachment, carefully enlarge the holes or slots in the deflector plate. You can also remove some of the material from the plate to further improve flow.
4. Use a metal file to smooth out any sharp edges.
5. Reinstall the muffler.

Pros:

• Can provide a significant increase in power.
• Doesn’t significantly increase noise levels.
• Can be done with basic tools.

Cons:

• Requires some skill and precision to modify the deflector plate.
• Can potentially damage the muffler if not done carefully.
• May require some trial and error to find the optimal configuration.

My Experience: This modification requires a bit more finesse than the previous ones. I’ve found that it’s best to start with small modifications and gradually increase the size of the holes or slots until you achieve the desired performance. Be careful not to remove too much material, as this can weaken the deflector plate.

Wood Processing Insight: This mod is particularly effective when processing larger diameter logs, where the engine needs to work harder to maintain chain speed.

4. The Dual Port Muffler: Unleashing the Beast (Carefully)

This modification involves creating a dual port muffler by adding a second outlet to the muffler. This is a more advanced modification that requires welding skills.

Why it works: By adding a second outlet, you’re essentially doubling the muffler’s surface area, allowing significantly more exhaust gases to escape. This dramatically reduces backpressure and allows the engine to breathe much easier, resulting in a substantial increase in power.

How to do it:

1. Remove the muffler from the chainsaw.
2. Choose a location for the second outlet. A good spot is usually on the opposite side of the existing outlet.
3. Using a drill with a hole saw, carefully cut a hole in the muffler. The hole should be the same size as the existing outlet.
4. Fabricate a new outlet using metal tubing or a pre-made muffler extension.
5. Weld the new outlet to the muffler.
6. Grind down any rough edges and smooth out the welds.
7. Reinstall the muffler.

Pros:

• Provides a significant increase in power.
• Can dramatically improve the chainsaw’s performance.

Cons:

• Requires welding skills and equipment.
• Can significantly increase noise levels.
• May require rejetting the carburetor to compensate for the increased airflow.
• Increases the risk of starting a fire in dry conditions.

My Experience: This is the most aggressive modification on the list, and it’s not for the faint of heart. I’ve done this modification on a few MS170s, and the power increase is definitely noticeable. However, it also significantly increases the noise level, and you’ll likely need to rejet the carburetor to prevent the engine from running lean.

Case Study: I once used a dual-port modified MS170 to clear a heavily overgrown area. The increased power made it much easier to cut through the thick brush and small trees, saving me a significant amount of time and effort. However, I had to be extra careful to avoid starting a fire, as the increased exhaust flow made the saw run much hotter.

Carburetor Tuning – The Critical Step: After a dual-port modification, the engine will likely run lean. This means it’s getting too much air and not enough fuel. A lean condition can cause the engine to overheat and potentially damage it. To correct this, you’ll need to adjust the carburetor. This typically involves adjusting the high-speed (H) and low-speed (L) needles on the carburetor. Start by turning the H needle counter-clockwise (richening the mixture) in small increments, and then test the saw. If the engine still bogs down or hesitates, continue to richen the mixture until it runs smoothly.

5. The Aftermarket Muffler: The Bolt-On Solution

This modification involves replacing the stock muffler with an aftermarket performance muffler.

Why it works: Aftermarket mufflers are designed to provide improved exhaust flow and performance compared to the stock muffler. They’re typically made from higher-quality materials and feature a less restrictive design.

How to do it:

1. Remove the stock muffler from the chainsaw.
2. Install the aftermarket muffler.
3. Tighten the mounting bolts to the manufacturer’s specifications.
4. Adjust the carburetor as needed.

Pros:

• Easy to install.
• Provides a noticeable increase in power.
• May not significantly increase noise levels.
• Can improve the chainsaw’s overall appearance.

Cons:

• Can be expensive.
• The quality of aftermarket mufflers can vary.
• May require some carburetor adjustments.

My Experience: I’ve used several aftermarket mufflers on MS170s, and I’ve generally been happy with the results. They’re a good option if you want to improve your saw’s performance without having to do any welding or fabrication. However, it’s important to choose a reputable brand and read reviews before purchasing an aftermarket muffler.

Market Trends: The aftermarket parts industry for small engines is booming, with a wide variety of performance mufflers available for the MS170. Some popular brands include Farmertec, Holzfforma, and Westech.

Data Point: Independent tests have shown that aftermarket mufflers can increase MS170 power output by 5-10%, depending on the specific model and the engine’s condition.

Fine-Tuning for Optimal Performance: The Carburetor Adjustment

Regardless of which muffler modification you choose, it’s crucial to adjust the carburetor to ensure that the engine is running properly. As I mentioned earlier, modifying the muffler changes the engine’s airflow, which can affect the air-fuel mixture. If the engine is running lean (too much air, not enough fuel), it can overheat and potentially damage the engine. If it’s running rich (too much fuel, not enough air), it can bog down and produce excessive smoke.

How to Adjust the Carburetor:

1. Locate the carburetor adjustment screws. They’re usually labeled “H” (high speed) and “L” (low speed). Some carburetors may also have an “LA” (low idle) screw.
2. Start by turning the “H” screw clockwise until it’s fully seated. Then, turn it counter-clockwise 1-1/2 turns.
3. Start the engine and let it warm up.
4. Adjust the “L” screw until the engine idles smoothly without stalling.
5. Make a test cut. If the engine bogs down or hesitates when you accelerate, turn the “H” screw counter-clockwise (richen the mixture) in small increments until it runs smoothly.
6. If the engine is running too fast at idle, adjust the “LA” screw until it idles at the correct speed.

Important Considerations:

• Make small adjustments and test the saw after each adjustment.
• Pay attention to the engine’s sound and performance.
• If you’re not comfortable adjusting the carburetor yourself, consult with a qualified mechanic.

Long-Term Maintenance: Keeping Your Modified Saw Running Smoothly

Once you’ve modified your MS170 muffler, it’s important to perform regular maintenance to keep it running smoothly.

• Clean the Air Filter: A dirty air filter restricts airflow and can cause the engine to run poorly. Clean the air filter regularly with soap and water.
• Replace the Spark Plug: A worn spark plug can cause the engine to misfire and lose power. Replace the spark plug every year or as needed.
• Clean the Muffler: Over time, carbon deposits can build up in the muffler, restricting exhaust flow. Clean the muffler periodically with a wire brush or solvent.
• Use Fresh Fuel: Use fresh, high-quality fuel with the correct oil mixture.
• Store the Saw Properly: When storing the saw for extended periods, drain the fuel tank and run the engine until it stalls to prevent fuel from gumming up the carburetor.

Legal and Environmental Considerations: Know the Rules

Before you modify your MS170 muffler, it’s important to be aware of the legal and environmental implications.

• Spark Arrestor Screens: As mentioned earlier, removing the spark arrestor screen can increase the risk of starting a fire in dry conditions. Many areas require spark arrestor screens on chainsaws, especially during fire season. Check your local regulations before removing the screen.
• Emissions Standards: Modifying the muffler can affect the chainsaw’s emissions. In some areas, it may be illegal to modify a chainsaw in a way that violates emissions standards.
• Noise Levels: Modifying the muffler can increase the chainsaw’s noise level. Be considerate of your neighbors and avoid using the saw in noise-sensitive areas.

The Bottom Line: Is a Muffler Mod Right for You?

Modifying your Stihl MS170 muffler can be a rewarding experience, allowing you to unleash a bit more power and improve your saw’s performance. However, it’s important to weigh the pros and cons before making any modifications.

If you’re looking for a simple and easy way to improve your saw’s performance, removing the spark arrestor screen or adding an additional outlet is a good option. If you’re more experienced and comfortable with welding and fabrication, a dual-port muffler can provide a significant increase in power. And if you want a hassle-free solution, an aftermarket muffler is a good choice.

Ultimately, the best modification for you will depend on your skills, budget, and needs. Just remember to prioritize safety, follow the instructions carefully, and adjust the carburetor as needed. And always be aware of the legal and environmental implications of your modifications.

So, there you have it – five expert muffler modifications for your Stihl MS170. I hope this article has been helpful and informative. Now get out there and make some sawdust! Just remember to be safe, responsible, and have fun!

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