MS391 Specs Compared: Power & Performance Unveiled (5 Key Facts)

As someone who’s spent countless hours in the woods, covered in sawdust and the scent of freshly cut timber, I understand the importance of a reliable chainsaw. Before diving into the nitty-gritty of cleaning it, though, let’s talk about why understanding its power and performance specs are so crucial.

MS 391 Specs Compared: Power & Performance Unveiled (5 Key Facts)

Choosing the right chainsaw is like picking the right tool for any job. You wouldn’t use a screwdriver to hammer a nail, and you wouldn’t use a small pruning saw to fell a large tree. Knowing the MS 391’s capabilities allows you to determine if it’s the right fit for your specific needs, preventing frustration, wasted time, and potential safety hazards.

1. Engine Power and Displacement: The Heart of the Matter

The MS 391 boasts a 64.1 cc (3.9 cu. in.) engine. This is a key factor in determining its cutting power. Displacement refers to the total volume swept by the pistons during one complete cycle. A larger displacement generally translates to more power.

Why it matters: More displacement means the chainsaw can handle larger logs and tougher wood types without bogging down.
My experience: I remember a job clearing fallen oak trees after a storm. My smaller chainsaw struggled, but a colleague with an MS 391 sliced through those thick trunks with ease. That’s the difference displacement makes.
Data point: The MS 391’s 64.1 cc engine produces around 4.4 bhp (brake horsepower). This is a significant step up from smaller, homeowner-grade chainsaws, typically in the 30-40 cc range.
Beginner’s definition: Think of displacement like the size of the engine in your car. A bigger engine generally means more power.

2. Power-to-Weight Ratio: Finding the Sweet Spot

While raw power is important, the power-to-weight ratio is equally crucial. The MS 391 weighs in at around 6.4 kg (14.1 lbs) without the bar and chain. This gives it a respectable power-to-weight ratio, meaning you get a good amount of cutting power without being overly burdened by the saw’s weight.

Why it matters: A good power-to-weight ratio allows for longer periods of use without excessive fatigue.
My experience: I once spent an entire day bucking firewood with a heavier, more powerful saw. By the end of the day, my arms felt like lead. A lighter saw with comparable power, like the MS 391, would have made a huge difference.
Data point: Compare the MS 391 to a professional-grade saw with a larger engine and heavier construction. While the professional saw might have more raw power, the MS 391’s lighter weight makes it more maneuverable for a wider range of tasks.
Beginner’s definition: Power-to-weight ratio is like comparing a sports car to a truck. The truck has more power, but the sports car is faster because it’s lighter.

3. Cutting Bar Length Options: Versatility in Action

The MS 391 can accommodate different bar lengths, typically ranging from 16 to 25 inches. This allows you to tailor the saw to the specific task at hand.

Why it matters: A longer bar is useful for felling larger trees, while a shorter bar is more maneuverable for limbing and smaller tasks.
My experience: I primarily use a 20-inch bar on my MS 391 for general firewood cutting. It provides a good balance between reach and maneuverability. However, I switch to a 16-inch bar when I’m doing more detailed work around the yard.
Data point: The optimal bar length depends on the diameter of the wood you’ll be cutting most frequently. As a general rule, the bar should be at least two inches longer than the diameter of the largest wood you plan to cut.
Beginner’s definition: The bar is the long metal piece that the chain runs around. A longer bar lets you cut thicker wood.

4. Fuel and Oil Capacity: Minimizing Downtime

The MS 391 has a fuel tank capacity of 0.68 liters (23 oz) and an oil tank capacity of 0.36 liters (12.2 oz). This allows for extended periods of use before needing to refuel or refill the bar oil.

Why it matters: Larger tank capacities mean less downtime, which is especially important when working on large projects or in remote locations.
My experience: I’ve been caught short on fuel in the middle of the woods more than once. Now I always make sure to fill both the fuel and oil tanks completely before starting any job.
Data point: The fuel consumption of the MS 391 varies depending on the type of wood being cut and the operator’s technique. However, you can generally expect to get around 45 minutes to an hour of continuous use on a full tank of fuel.
Beginner’s definition: The fuel tank holds the gasoline that powers the engine, and the oil tank holds the bar oil that lubricates the chain.

5. Anti-Vibration System: Comfort and Control

The MS 391 features Stihl’s anti-vibration system, which helps to reduce operator fatigue and improve control. This system uses rubber buffers to isolate the engine and cutting attachment from the handles.

Why it matters: Reduced vibration means less strain on your hands and arms, allowing you to work longer and more safely.
My experience: I’ve used chainsaws without anti-vibration systems, and the difference is night and day. The vibration can be so intense that it makes your hands go numb, which is not only uncomfortable but also dangerous.
Data point: Studies have shown that anti-vibration systems can significantly reduce the risk of developing hand-arm vibration syndrome (HAVS), a painful and debilitating condition.
Beginner’s definition: The anti-vibration system is designed to reduce the amount of shaking you feel while using the chainsaw.

Deep Dive: Understanding Key Concepts

Now that we’ve covered the key specs, let’s delve into some essential concepts that will help you better understand and utilize the MS 391.

Green Wood vs. Seasoned Wood

Green Wood: This is freshly cut wood that still contains a high amount of moisture. It’s heavier, more difficult to split, and tends to warp and crack as it dries.
Seasoned Wood: This is wood that has been allowed to dry for a period of time, typically six months to a year. It’s lighter, easier to split, and burns more efficiently.
Why it matters: Cutting green wood puts more strain on your chainsaw. Seasoned wood is easier to process and provides better heat output when burned.
My experience: I once tried to split a large oak log that was still green. It was like trying to split a rock. After letting it season for a year, it split like butter.
Data point: Green wood can have a moisture content of 50% or higher, while seasoned wood typically has a moisture content of 20% or less.
Beginner’s definition: Green wood is wet and fresh, seasoned wood is dry and ready to burn.

Chain Types and Sharpening

Chain Types: Different chain types are designed for different purposes. Some are better for cutting hardwoods, while others are better for cutting softwoods.
Chain Sharpening: A sharp chain is essential for efficient and safe cutting. A dull chain can cause the saw to kickback and can also put unnecessary strain on the engine.
Why it matters: Using the right chain type and keeping it sharp will improve cutting performance and extend the life of your chainsaw.
My experience: I learned the hard way that a dull chain is a dangerous chain. I was cutting a small branch when the saw kicked back and nearly hit me in the face. Since then, I’ve made it a habit to sharpen my chain regularly.
Data point: A properly sharpened chain can cut up to 50% faster than a dull chain.
Beginner’s definition: The chain is the part of the chainsaw that actually cuts the wood. Keeping it sharp is very important.

Felling Techniques

Felling: The process of cutting down a tree safely and efficiently.
Why it matters: Proper felling techniques are essential for preventing accidents and ensuring that the tree falls in the desired direction.
My experience: I’ve seen firsthand the damage that can be caused by improper felling techniques. I once witnessed a tree fall in the wrong direction and crush a nearby car.
Data point: Felling is one of the most dangerous activities in logging. It’s important to receive proper training before attempting to fell a tree.
Beginner’s definition: Felling is the act of cutting down a tree. It’s important to do it safely.

Step-by-Step Guides: Putting Knowledge into Action

Now, let’s move on to some practical step-by-step guides that will help you utilize the MS 391 effectively.

Felling a Small Tree (Up to 8 Inches in Diameter)

Tools Needed:

Stihl MS 391 Chainsaw with appropriate bar length
Helmet with face shield
Hearing protection
Steel-toed boots
Gloves
Wedges (optional)

Steps:

Assess the Tree: Check for any hazards, such as dead branches, power lines, or other trees that could be affected by the falling tree.
Plan Your Escape Route: Identify two escape routes that are at a 45-degree angle to the direction of the fall.
Clear the Area: Remove any brush or debris that could obstruct your movement or the fall of the tree.
Make the Notch Cut: Cut a notch on the side of the tree facing the direction you want it to fall. The notch should be about one-third of the tree’s diameter.
Make the Back Cut: Cut from the opposite side of the tree, about two inches above the notch. Leave a hinge of wood to control the direction of the fall.
Insert Wedges (Optional): If the tree doesn’t start to fall on its own, insert wedges into the back cut and tap them with a hammer to encourage the tree to fall.
Retreat Along Your Escape Route: As the tree begins to fall, retreat quickly and safely along your pre-planned escape route.

My experience: Always double-check your surroundings before felling a tree. I once almost tripped over a hidden root while retreating from a falling tree.

Splitting Firewood with a Hydraulic Splitter

Tools Needed:

Hydraulic Log Splitter
Gloves
Safety Glasses
Steel-toed boots
Stihl MS 391 Chainsaw for cutting logs to length

Steps:

Cut Logs to Length: Use your MS 391 to cut the logs to the desired length for your firewood stove or fireplace. It saves a lot of time and effort, especially when dealing with large or knotty logs.
Debarking Logs with a Draw Knife

Tools Needed:
- Draw Knife
- Work Gloves
- Log Stand or Sawhorse
- Stihl MS 391 Chainsaw for initial log preparation
Steps:
1. Secure the Log: Place the log on a log stand or sawhorse to elevate it and make it easier to work with.
2. Position Yourself: Stand facing the log with your feet shoulder-width apart.
3. Grip the Draw Knife: Hold the draw knife with both hands, with the blade facing towards you.
4. Pull the Draw Knife: Pull the draw knife towards you, shaving off the bark in long, even strokes.
5. Adjust Your Angle: Adjust the angle of the draw knife as needed to follow the contours of the log.
6. Repeat as Needed: Repeat the process until all of the bark has been removed from the log.
My experience: Debarking logs can be a time-consuming process, but it’s worth it if you want to create clean, smooth lumber or firewood.

Drying Methods for Firewood
- Air Drying: The most common method, involving stacking firewood in a well-ventilated area and allowing it to dry naturally.
- Kiln Drying: A faster method that uses heat to dry the firewood. This is typically done commercially.
- Why it matters: Proper drying is essential for producing high-quality firewood that burns efficiently and cleanly.
- My experience: I’ve found that air drying is the most cost-effective method for drying firewood. However, it’s important to stack the wood properly to ensure good airflow.
- Data point: Air drying typically takes six months to a year, while kiln drying can be done in a matter of days.
- Beginner’s definition: Drying firewood removes the moisture, making it burn better.
Safety Considerations
- Personal Protective Equipment (PPE): Always wear appropriate PPE, including a helmet, face shield, hearing protection, gloves, and steel-toed boots.
- Chain Saw Safety: Follow all safety guidelines for operating a chainsaw, including keeping a firm grip on the saw, maintaining a safe distance from others, and never cutting above shoulder height.
- Safe Felling Practices: Use proper felling techniques to ensure that the tree falls in the desired direction.
- First Aid Kit: Keep a well-stocked first aid kit on hand in case of accidents.
Strategic Advantages of Using the MS 391
- Versatility: The MS 391 is a versatile chainsaw that can be used for a wide range of tasks, from felling small trees to bucking firewood.
- Power and Performance: The MS 391 offers a good balance of power and performance, making it suitable for both homeowners and professionals.
- Durability: Stihl chainsaws are known for their durability and reliability. The MS 391 is built to last, even under demanding conditions.
- Ease of Use: The MS 391 is relatively easy to use, even for beginners. It features a simple starting system and ergonomic design.
Costs and Material Specs
- MS 391 Chainsaw: The cost of an MS 391 chainsaw typically ranges from $600 to $800, depending on the bar length and any included accessories.
- Fuel: Chainsaws typically require a mixture of gasoline and 2-cycle oil. The ratio is usually 50:1.
- Bar Oil: Bar oil is used to lubricate the chain and bar. It’s important to use a high-quality bar oil to prevent wear and tear.
- Wood Moisture Content: The ideal moisture content for firewood is 20% or less.
Case Study: From Tree to Firewood – A Complete Process

Let’s walk through a case study of taking a fallen tree and turning it into usable firewood, utilizing the MS 391 at each stage.

Scenario: A medium-sized oak tree (approximately 12 inches in diameter) has fallen in your yard due to a storm.

Steps:
1. Assessment and Planning: Evaluate the situation. Ensure the tree is not resting on any structures or power lines. Plan your felling cuts if necessary to safely remove any remaining attached portions of the tree.
2. Limbing: Use the MS 391 to remove all the branches from the fallen tree. Start from the base and work your way up, cutting the branches close to the trunk.
3. Bucking: Cut the trunk into manageable lengths for splitting. I typically cut my firewood into 16-inch lengths, as they fit well in my wood stove. Use the MS 391 to buck the logs to the desired length.
4. Splitting: Split the logs using a hydraulic log splitter. Place each log on the splitter and activate the machine to split it into smaller pieces.
5. Stacking: Stack the split firewood in a well-ventilated area to allow it to season properly. I prefer to stack my firewood in rows, with spaces between the rows to promote airflow.
6. Drying: Allow the firewood to dry for at least six months, or preferably a year, before burning it. Check the moisture content with a moisture meter to ensure it’s below 20%.
MS 391’s Role: The MS 391 is the workhorse of this entire process. It’s used for limbing, bucking, and any necessary felling cuts. Its power and reliability make it an ideal tool for this type of work.

Challenges Faced by Global DIYers and Small-Scale Logging Businesses
- Access to Equipment: Chainsaws and other wood processing equipment can be expensive, especially for DIYers and small-scale businesses in developing countries.
- Training and Safety: Proper training in chainsaw operation and safe felling techniques is essential, but it’s not always readily available or affordable.
- Environmental Regulations: Logging and firewood production are subject to environmental regulations in many countries. It’s important to be aware of these regulations and to comply with them.
- Market Access: Small-scale logging businesses may face challenges in accessing markets for their products.
Next Steps and Implementation Guidance
- Start Small: If you’re new to wood processing, start with small projects and gradually work your way up to larger ones.
- Invest in Quality Equipment: Invest in high-quality equipment, such as a Stihl MS 391 chainsaw, to ensure safety and efficiency.
- Get Trained: Take a chainsaw safety course to learn proper operating techniques and safe felling practices.
- Follow Safety Guidelines: Always follow safety guidelines when operating a chainsaw or other wood processing equipment.
- Season Your Firewood: Allow your firewood to season properly before burning it to ensure efficient and clean burning.
- Experiment with Different Techniques: Don’t be afraid to experiment with different techniques to find what works best for you.
Final Thoughts

The Stihl MS 391 is a capable and versatile chainsaw that can be a valuable asset for anyone involved in wood processing or firewood preparation. By understanding its key specs, mastering essential techniques, and prioritizing safety, you can harness its power to efficiently and safely tackle a wide range of tasks. Remember to always wear your PPE, follow safety guidelines, and take your time to learn the ropes. With practice and patience, you’ll be well on your way to becoming a proficient wood processor.

MS391 Specs Compared: Power & Performance Unveiled (5 Key Facts)