MS391 Bar Size Guide (3 Expert Tips For Optimal Chainsaw Use)

Unlock Your Chainsaw’s Full Potential: Mastering the MS391 Bar Size for Peak Performance

Ever felt your chainsaw was fighting you, bogging down in the cut, or just not performing as it should? I’ve been there. For years, I wrestled with similar issues, blaming everything from dull chains to hard wood. Then, I discovered the critical role of the guide bar size. Choosing the right bar length for your Stihl MS391 can drastically improve cutting efficiency, safety, and the overall lifespan of your saw. This guide will provide you with expert tips to optimize your MS391 chainsaw use.

Understanding the User Intent

The user intent behind searching for an “MS391 Bar Size Guide” is multifaceted:

Decoding the MS391: A Deep Dive into Chainsaw Mechanics

Before we jump into bar sizes, let’s get familiar with the MS391. This saw is a workhorse, known for its reliable performance in various conditions. However, understanding its limitations is key to getting the most out of it.

Engine Specs and Power Output

The Stihl MS391 is equipped with a 64.1 cc engine. This is important because the engine’s power dictates the maximum bar length it can effectively handle. A longer bar requires more power to drive the chain through the wood.

Engine Displacement: 64.1 cc
Power Output: 3.3 kW (4.4 bhp)
Weight (without bar and chain): 6.4 kg (14.1 lbs)

These specs tell us that the MS391 is a mid-range saw suitable for felling small to medium-sized trees, bucking firewood, and general property maintenance.

Chain Pitch and Gauge: The Unsung Heroes

The chain pitch and gauge are crucial for smooth cutting and efficient chip removal. The MS391 typically uses a .325″ pitch chain with a .063″ gauge.

Pitch: The distance between three consecutive rivets divided by two.
Gauge: The thickness of the drive links that fit into the guide bar groove.

Using the correct chain pitch and gauge ensures the chain fits properly on the sprocket and in the bar groove, preventing premature wear and potential accidents.

The Guide Bar: Your Chainsaw’s Cutting Edge

The guide bar isn’t just a piece of metal; it’s the foundation of your cutting performance. Choosing the right bar length and type can make a world of difference.

Understanding Bar Length and Its Impact

Bar length is the usable cutting length of the guide bar, measured from the tip to where it enters the saw body. The MS391 can accommodate bar lengths ranging from 16 inches to 25 inches.

Shorter Bars (16-18 inches): Ideal for limbing, pruning, and cutting small diameter wood. They offer better control and maneuverability.
Medium Bars (20-22 inches): A versatile choice for felling small to medium-sized trees and bucking firewood.
Longer Bars (24-25 inches): Suitable for felling larger trees, but require more power and skill to handle safely.

Bar Types: Laminated vs. Solid

Guide bars come in two main types: laminated and solid.

Laminated Bars: Constructed from multiple layers of steel welded together. They are lighter and more affordable, making them suitable for occasional use.
Solid Bars: Made from a single piece of steel, offering greater durability and resistance to bending. They are preferred for heavy-duty applications.

For the MS391, a laminated bar is typically sufficient for most users, but if you frequently work with hardwoods or large trees, a solid bar might be a worthwhile investment.

The Nose of the Bar: Sprocket vs. Hard Nose

The nose of the guide bar can be either a sprocket nose or a hard nose.

Sprocket Nose: Contains a sprocket that helps reduce friction and improve cutting speed. It’s ideal for general purpose cutting.
Hard Nose: A solid piece of steel, offering greater durability and resistance to wear. It’s preferred for abrasive conditions or when cutting dirty wood.

The MS391 generally performs well with a sprocket nose bar, as it provides a good balance of cutting speed and durability.

Expert Tip #1: Matching Bar Size to the Task

The first key to optimal chainsaw use is selecting the right bar size for the job at hand. I learned this the hard way, trying to fell a large oak with an undersized bar. It was slow, inefficient, and downright dangerous.

Felling Trees: Size Matters

When felling trees, the bar length should be at least slightly longer than the diameter of the tree you intend to cut. This allows you to make a clean, controlled cut without burying the saw body in the wood.

Small Trees (up to 12 inches diameter): 16-18 inch bar
Medium Trees (12-24 inches diameter): 20-22 inch bar
Large Trees (over 24 inches diameter): 24-25 inch bar

Remember, it’s always better to err on the side of a slightly longer bar than a shorter one.

Bucking Firewood: Efficiency is Key

Bucking firewood is where you’ll spend most of your time with a chainsaw. A 20-22 inch bar is a good all-around choice for bucking logs of various sizes.

Small Logs (up to 8 inches diameter): 16-18 inch bar
Medium Logs (8-16 inches diameter): 20-22 inch bar
Large Logs (over 16 inches diameter): 24-25 inch bar

For maximum efficiency, consider using a bucking sawhorse to elevate the logs and make cutting easier.

Limbing and Pruning: Maneuverability is Paramount

Limbing and pruning require precision and control. A shorter bar (16-18 inches) is ideal for these tasks, as it allows you to maneuver the saw in tight spaces and make accurate cuts.

Small Branches (up to 4 inches diameter): 16 inch bar
Medium Branches (4-8 inches diameter): 18 inch bar

Always use proper safety gear, including gloves, eye protection, and a helmet, when limbing or pruning overhead branches.

Case Study: The Overpowered Chainsaw

I once witnessed a homeowner struggling to prune small branches with a 24-inch bar on his MS391. He was constantly fighting the weight and length of the saw, resulting in sloppy cuts and near misses. After switching to a 16-inch bar, his control and accuracy improved dramatically, making the task much safer and more efficient.

Expert Tip #2: Maintaining Your Guide Bar for Longevity

A well-maintained guide bar will last longer, cut better, and reduce the risk of accidents. Here are some essential maintenance practices:

Cleaning and Deburring: Removing the Grime

Regularly clean your guide bar to remove sawdust, pitch, and other debris. Use a stiff brush or a putty knife to scrape away the buildup.

Frequency: After each use
Tools: Stiff brush, putty knife, solvent (optional)

Also, check for burrs along the edges of the bar groove. These can damage the chain and reduce cutting efficiency. Use a flat file to carefully remove any burrs.

Bar Rail Dressing: Ensuring Smooth Chain Travel

Bar rail dressing involves filing the edges of the bar rails to ensure they are square and smooth. This allows the chain to travel smoothly and evenly, reducing wear and tear.

Frequency: Every few uses or when the chain feels tight
Tools: Flat file, bar rail dresser (optional)

Use a flat file to carefully file the edges of the bar rails, keeping the file perpendicular to the bar. Avoid rounding the edges, as this can cause the chain to wobble.

Sprocket Nose Lubrication: Keeping Things Moving

If your guide bar has a sprocket nose, it’s essential to keep it lubricated. The sprocket nose contains a bearing that can seize up if it’s not properly greased.

Frequency: Every few uses or when the sprocket feels stiff
Tools: Grease gun, multipurpose grease

Use a grease gun to inject grease into the lubrication hole on the sprocket nose. Rotate the sprocket to distribute the grease evenly.

Flipping the Bar: Even Wear Distribution

Flipping the guide bar regularly helps distribute wear evenly across both sides. This prevents one side from becoming excessively worn, which can cause the chain to cut unevenly.

Frequency: Every few uses
Procedure: Remove the bar, flip it over, and reinstall it

This simple practice can significantly extend the life of your guide bar.

Data Point: The Impact of Bar Maintenance

A study conducted by the Forest Engineering Research Institute of Canada (FERIC) found that regular bar maintenance can increase the lifespan of a guide bar by up to 50%. This translates to significant cost savings over time.

Expert Tip #3: Understanding Wood Types and Their Impact on Bar Selection

The type of wood you’re cutting can also influence your bar size selection. Hardwoods require more power to cut than softwoods, so you might need a shorter bar to maintain optimal cutting speed.

Hardwood vs. Softwood: A Matter of Density

Hardwoods, such as oak, maple, and hickory, are denser and more resistant to cutting than softwoods, such as pine, fir, and spruce.

Hardwoods: Require more power, generate more heat, and dull the chain faster.
Softwoods: Easier to cut, generate less heat, and are less abrasive.

When cutting hardwoods, consider using a shorter bar to reduce the load on the engine. Also, ensure your chain is sharp and well-lubricated.

Abrasive Wood: Extra Care Required

Some types of wood, such as redwood and cedar, contain abrasive compounds that can accelerate wear on the guide bar and chain.

Redwood: Contains silica, which is highly abrasive.
Cedar: Contains oils that can attract dirt and debris.

When cutting abrasive wood, clean your guide bar and chain frequently to remove buildup. Also, consider using a hard nose bar, as it’s more resistant to wear.

Frozen Wood: A Winter Challenge

Cutting frozen wood presents unique challenges. Frozen wood is harder and more brittle than unfrozen wood, making it more difficult to cut.

Frozen Wood: Requires more power, increases the risk of kickback, and can damage the chain.

When cutting frozen wood, use a sharp chain and a shorter bar to reduce the load on the engine. Also, be extra cautious to avoid kickback.

Personal Story: The Frozen Oak Debacle

I once attempted to fell a frozen oak tree in the middle of winter with a dull chain and a 24-inch bar. The saw bogged down repeatedly, and I nearly lost control several times. After switching to a sharp chain and a 20-inch bar, the cutting became much smoother and safer.

Safety First: Protecting Yourself and Others

Chainsaw safety should always be your top priority. Here are some essential safety precautions to follow:

Personal Protective Equipment (PPE): Your First Line of Defense

Always wear appropriate PPE when operating a chainsaw, including:

Helmet: Protects your head from falling debris.
Eye Protection: Protects your eyes from flying chips and sawdust.
Hearing Protection: Protects your ears from the loud noise of the chainsaw.
Gloves: Protect your hands from cuts and abrasions.
Chainsaw Chaps: Protect your legs from accidental cuts.
Steel-Toed Boots: Protect your feet from falling logs and sharp objects.

Kickback Prevention: Avoiding the Unexpected

Kickback is a sudden, uncontrolled movement of the chainsaw that can cause serious injury. To prevent kickback:

Avoid Cutting with the Tip of the Bar: The tip of the bar is the most vulnerable to kickback.
Maintain a Firm Grip: Keep both hands firmly on the saw handles.
Stand to the Side of the Cut: Avoid standing directly behind the saw.
Use a Reduced-Kickback Chain: These chains have special features that reduce the risk of kickback.

Safe Cutting Techniques: Mastering the Basics

Use proper cutting techniques to maintain control of the chainsaw and avoid accidents.

Always Cut with a Sharp Chain: A dull chain is more likely to kick back or bind.
Use a Stable Stance: Keep your feet firmly planted and your weight balanced.
Plan Your Cut: Think about where the log will fall and how to avoid obstacles.
Never Cut Above Shoulder Height: This increases the risk of losing control of the saw.

Industry Statistic: The Importance of Safety Training

According to the Occupational Safety and Health Administration (OSHA), chainsaw-related injuries account for approximately 36,000 emergency room visits each year in the United States. Proper safety training can significantly reduce the risk of these injuries.

Beyond the Bar: Optimizing Your MS391 for Peak Performance

Choosing the right bar size is just one piece of the puzzle. To truly optimize your MS391, you need to consider other factors as well.

Chain Selection: Matching the Chain to the Task

The type of chain you use can have a significant impact on cutting performance.

Full Chisel Chains: Offer the fastest cutting speed but are more prone to dulling.
Semi-Chisel Chains: Provide a good balance of cutting speed and durability.
Low-Kickback Chains: Designed to reduce the risk of kickback, but cut slower than other types of chains.

For general purpose cutting, a semi-chisel chain is a good choice. If you need maximum cutting speed, use a full chisel chain, but be prepared to sharpen it more frequently.

Fuel and Oil: Keeping the Engine Running Smoothly

Use high-quality fuel and oil to ensure your MS391 runs smoothly and reliably.

Fuel: Use a mixture of gasoline and two-stroke oil, following the manufacturer’s recommendations.
Oil: Use a bar and chain oil specifically designed for chainsaws.

Avoid using old or contaminated fuel, as this can damage the engine. Also, check the oil level frequently and refill as needed.

Air Filter Maintenance: Breathing Easy

A clean air filter is essential for proper engine performance. A clogged air filter can restrict airflow, causing the engine to run poorly or overheat.

Frequency: Clean the air filter after each use or more frequently in dusty conditions.
Procedure: Remove the air filter and clean it with compressed air or soapy water.

Allow the air filter to dry completely before reinstalling it.

Original Research: The Impact of Fuel Quality

In a small-scale experiment I conducted, I compared the performance of my MS391 using two different types of fuel: premium gasoline and regular gasoline. The saw ran noticeably smoother and produced more power with the premium gasoline. This suggests that using high-quality fuel can improve chainsaw performance.

Project Planning and Execution: A Step-by-Step Guide

Now that you understand the importance of bar size and chainsaw maintenance, let’s put it all together with a step-by-step guide to project planning and execution.

Step 1: Assess the Task

Before you start cutting, take the time to assess the task at hand.

Identify the Type of Wood: Is it hardwood or softwood? Is it frozen or abrasive?
Determine the Diameter of the Wood: This will help you choose the right bar size.
Identify Potential Hazards: Are there any obstacles or power lines nearby?

Step 2: Select the Appropriate Bar and Chain

Based on your assessment, select the appropriate bar size and chain type.

Refer to the Bar Size Guide: Use the guidelines provided earlier in this article.
Choose the Right Chain Type: Select a chain that is appropriate for the type of wood you’re cutting.
Ensure the Chain is Sharp: A sharp chain is essential for safe and efficient cutting.

Step 3: Prepare the Work Area

Prepare the work area to ensure a safe and efficient cutting environment.

Clear Obstacles: Remove any obstacles that could impede your movement or create a hazard.
Set Up a Stable Work Surface: Use a bucking sawhorse or other stable surface to elevate the wood.
Establish an Escape Route: Plan an escape route in case of an emergency.

Step 4: Follow Safe Cutting Techniques

Follow safe cutting techniques to maintain control of the chainsaw and avoid accidents.

Wear Appropriate PPE: Always wear a helmet, eye protection, hearing protection, gloves, chainsaw chaps, and steel-toed boots.
Use a Stable Stance: Keep your feet firmly planted and your weight balanced.
Avoid Cutting with the Tip of the Bar: The tip of the bar is the most vulnerable to kickback.
Plan Your Cut: Think about where the log will fall and how to avoid obstacles.

Step 5: Clean Up and Maintain Your Equipment

After you’ve finished cutting, clean up the work area and maintain your equipment.

Remove Sawdust and Debris: Clean the chainsaw and the work area to remove sawdust and debris.
Sharpen the Chain: Sharpen the chain if it has become dull.
Lubricate the Guide Bar: Lubricate the guide bar and sprocket nose.
Store the Chainsaw Properly: Store the chainsaw in a safe and secure location.

Practical Tip: The Importance of a Sharp Chain

A sharp chain is not only more efficient, but it’s also safer. A dull chain requires more force to cut, increasing the risk of kickback and other accidents. Sharpen your chain regularly to maintain optimal performance and safety.

Firewood Seasoning Techniques and Safety Considerations

Once you’ve bucked your firewood, it’s essential to season it properly before burning it. Seasoning reduces the moisture content of the wood, making it burn more efficiently and produce less smoke.

Understanding Moisture Content Dynamics

Freshly cut wood can contain up to 50% moisture content. Seasoning reduces the moisture content to around 20%, which is ideal for burning.

Freshly Cut Wood: High moisture content, difficult to ignite, produces a lot of smoke.
Seasoned Wood: Low moisture content, easy to ignite, produces less smoke and more heat.

Seasoning Methods: Air Drying vs. Kiln Drying

The two main methods of seasoning firewood are air drying and kiln drying.

Air Drying: The most common method, involves stacking the wood in a well-ventilated area and allowing it to dry naturally.
Kiln Drying: A faster method, involves drying the wood in a kiln using heat.

Air drying typically takes 6-12 months, depending on the type of wood and the climate. Kiln drying can be completed in a matter of days.

Stacking Techniques: Maximizing Airflow

Proper stacking is essential for efficient air drying.

Elevate the Wood: Stack the wood on pallets or other supports to allow air to circulate underneath.
Stack in a Single Row: Avoid stacking the wood in large piles, as this can restrict airflow.
Leave Space Between Rows: Leave space between rows to allow air to circulate freely.
Cover the Top: Cover the top of the stack with a tarp to protect the wood from rain and snow.

Safety Considerations: Preventing Mold and Pests

When seasoning firewood, it’s important to take precautions to prevent mold and pests.

Choose a Sunny Location: Sunlight helps to kill mold and pests.
Remove Bark: Removing the bark can help the wood dry faster and reduce the risk of pests.
Treat with Borax: Borax can be used to treat the wood and prevent mold and pests.

Data-Backed Content: The Fuel Value of Seasoned Firewood

According to the U.S. Department of Energy, seasoned firewood can produce up to 25% more heat than unseasoned firewood. This translates to significant cost savings over time.

Logging Tool Selection and Maintenance Best Practices

Beyond the chainsaw, there are other essential logging tools that can make your wood processing tasks easier and safer.

Felling Axes and Wedges: Bringing Trees Down Safely

Felling axes and wedges are used to help fell trees in a controlled manner.

Felling Axe: Used to make the initial cuts in the tree trunk.
Wedges: Used to prevent the tree from pinching the saw blade and to help direct the fall of the tree.

Choose a felling axe with a sharp blade and a comfortable handle. Use wedges made of plastic or aluminum, as steel wedges can damage the saw chain.

Log Splitters: Making Firewood Preparation Easier

Log splitters are used to split logs into smaller pieces for firewood.

Manual Log Splitters: Operated by hand, suitable for splitting small logs.
Hydraulic Log Splitters: Powered by a hydraulic pump, capable of splitting large logs.

Choose a log splitter that is appropriate for the size and type of logs you’ll be splitting. Always wear safety glasses and gloves when operating a log splitter.

Cant Hooks and Log Lifters: Moving Heavy Logs

Cant hooks and log lifters are used to move and position heavy logs.

Cant Hook: Used to roll logs.
Log Lifter: Used to lift logs.

Choose cant hooks and log lifters with sturdy construction and comfortable handles.

Comparison: Manual vs. Hydraulic Splitters

Feature	Manual Log Splitter	Hydraulic Log Splitter
Power Source	Human	Hydraulic Pump
Log Size	Small	Large
Speed	Slow	Fast
Effort	High	Low
Cost	Low	High

Conclusion: Mastering the MS391 for Woodworking Success

Choosing the right bar size for your Stihl MS391 is crucial for optimizing performance, safety, and longevity. By understanding the engine specs, bar types, and wood properties, you can make informed decisions that will improve your cutting efficiency and reduce the risk of accidents. Remember to maintain your guide bar regularly, use proper safety gear, and follow safe cutting techniques. With these expert tips, you’ll be well on your way to mastering the MS391 and achieving woodworking success. Now go out there and put these tips into action. Your chainsaw – and your back – will thank you.