Stihl MS 291 Chain Size Guide: Bar & Chain Upsize Tips (Pro Hacks)

Let’s dive into the world of chainsaw customization, specifically focusing on the Stihl MS 291. Upgrading or simply replacing the bar and chain can seem daunting, but I’m here to demystify the process and make it as smooth as possible. We’ll cover everything from understanding the stock specifications to confidently choosing an upsized bar and chain that will enhance your saw’s performance. I’ll share some pro hacks I’ve learned over the years, gleaned from countless hours in the woods, and from working with seasoned loggers.

Stihl MS 291 Chain Size Guide: Bar & Chain Upsize Tips (Pro Hacks)

The Stihl MS 291 is a workhorse, a popular choice for both homeowners and professionals due to its balance of power and weight. But just like any tool, its performance can be optimized with the right setup. This guide is your go-to resource for understanding bar and chain sizes, and how to make informed decisions about upsizing for specific tasks.

Understanding the Stock Configuration

Before we start thinking about upgrades, it’s crucial to understand the factory-recommended specifications for the Stihl MS 291. Sticking to these ensures your saw operates as intended and minimizes the risk of damage or injury.

Stock Bar Length: Typically, the MS 291 comes with a 16-inch or 18-inch bar. However, some retailers might offer it with a 20-inch bar. Always check your saw’s manual or the Stihl website for the definitive specification for your specific model.
Chain Pitch: This refers to the distance between any three consecutive rivets on the chain, divided by two. The standard pitch for the MS 291 is .325″.
Chain Gauge: This is the thickness of the drive links, which fit into the bar groove. The standard gauge for the MS 291 is .063″ (1.6mm).
Drive Link Count: This varies depending on the bar length. For a 16-inch bar, you’ll typically need 62 drive links; an 18-inch bar requires 68 drive links; and a 20-inch bar needs 74 drive links.

Why are these specifications important? Using the wrong pitch or gauge can damage your sprocket, bar, and chain, not to mention the potential safety hazards. I once saw a guy try to force a .058″ gauge chain onto a bar designed for .063″. The chain bound up, the saw kicked back violently, and he ended up with a nasty bruise and a damaged bar. Lesson learned: always double-check those specs!

Deciding to Upsize: When and Why

Upsizing your bar and chain is not always the best move, but it can be beneficial in certain situations. Here’s when you might consider it:

Cutting Larger Diameter Logs: If you frequently work with logs that are close to the maximum cutting capacity of your current bar, upsizing can make the job easier and more efficient. It reduces the need for multiple passes and allows you to fell larger trees more safely.
Increased Productivity: A longer bar can increase your reach and allow you to cut more wood with each pass. This can be a significant advantage if you’re processing large quantities of firewood or working on a logging project.
Specific Cutting Techniques: Certain cutting techniques, like milling lumber, often require a longer bar for optimal results.

However, there are downsides to consider:

Reduced Power: A longer bar requires more power to drive the chain effectively. If your saw is already struggling, upsizing can bog it down and reduce cutting speed.
Increased Weight: A longer bar and chain add weight to the saw, which can lead to fatigue and reduced maneuverability, especially during extended use.
Increased Risk of Kickback: Longer bars can increase the risk of kickback, especially for inexperienced users.

My personal experience: I once upsized the bar on my MS 291 from 18 inches to 20 inches, thinking it would make short work of some large oak logs I needed to split for firewood. While it did handle the larger diameter logs more easily, I quickly realized the saw was working harder, and my arms were getting tired much faster. I also noticed a slight decrease in cutting speed, particularly when cutting hardwoods. After that experience, I reserve the 20-inch bar for only when I really need the extra reach and cutting capacity.

Choosing the Right Upsized Bar and Chain

If you’ve decided that upsizing is the right choice for your needs, here’s how to select the appropriate bar and chain:

Consider the Saw’s Power: The MS 291 has a 56.5 cc engine, which is respectable but not unlimited. I generally recommend sticking to a maximum bar length of 20 inches for optimal performance. Going beyond that can strain the engine and reduce its lifespan.
Maintain the Correct Pitch and Gauge: This is non-negotiable. Always use a chain with a .325″ pitch and a .063″ gauge to match the sprocket on your saw.
Calculate the Correct Drive Link Count: Use the following formula to determine the number of drive links you’ll need:
- Drive Link Count = (Bar Length in Inches x 2.5) + 2 (This is an approximate formula, always double-check with the bar manufacturer’s specifications)
For example, for a 20-inch bar:
- Drive Link Count = (20 x 2.5) + 2 = 52 drive links.
Note: Bar manufacturers often list the number of drive links directly on the bar itself or in their product descriptions. This is the most reliable way to determine the correct count.
Choose a Reputable Brand: Stick with well-known brands like Stihl, Oregon, or Husqvarna. These brands offer high-quality bars and chains that are designed to withstand the rigors of professional use. I’ve found that cheaper, off-brand chains tend to stretch more easily, dull faster, and are more prone to breakage.

Pro Tip: When upsizing, consider investing in a bar with a replaceable sprocket nose. This can significantly extend the life of the bar, as the sprocket nose is often the first part to wear out.

Installation and Adjustment

Installing a new bar and chain on your Stihl MS 291 is a relatively straightforward process, but it’s important to follow the correct steps to ensure safety and proper operation.

Safety First: Always wear gloves and safety glasses when handling chainsaws. Disconnect the spark plug wire to prevent accidental starting.
Remove the Old Bar and Chain: Loosen the bar nuts on the side of the saw with the provided wrench. Remove the side cover, and then carefully remove the old bar and chain.
Clean the Saw: Use a brush to clean any sawdust, dirt, or debris from the bar mounting surface, sprocket, and chain tensioning mechanism. This will ensure proper alignment and tensioning.
Install the New Bar: Place the new bar onto the mounting studs, making sure the chain tensioning pin aligns with the hole in the bar.
Install the New Chain: Drape the chain around the sprocket and into the bar groove, making sure the cutting teeth are facing in the correct direction (they should point forward at the top of the bar).
Reinstall the Side Cover: Place the side cover back onto the saw and tighten the bar nuts finger-tight.
Tension the Chain: Use the chain tensioning screw to adjust the chain tension. The chain should be snug against the bar, but you should still be able to pull it around the bar by hand. A good rule of thumb is to pull the chain away from the bar in the middle. There should be about 1/8″ to 1/4″ of daylight between the chain and the bar.
Tighten the Bar Nuts: Once you’re satisfied with the chain tension, tighten the bar nuts securely with the wrench.
Check the Tension Again: After tightening the bar nuts, double-check the chain tension. It may need to be adjusted slightly.
Lubricate the Chain: Fill the chain oil reservoir with bar and chain oil. Start the saw and run it at idle speed for a few seconds to allow the oil to circulate.

Common Mistakes:

Over-tensioning the chain: This can cause excessive wear on the bar, chain, and sprocket, and can even lead to chain breakage.
Under-tensioning the chain: This can cause the chain to derail from the bar, which is dangerous.
Forgetting to lubricate the chain: Running the chain without oil will quickly damage it and can also damage the bar.

Maintaining Your Upsized Bar and Chain

Proper maintenance is essential to ensure the longevity and performance of your upsized bar and chain.

Sharpen the Chain Regularly: A sharp chain is a safe chain. Dull chains require more force to cut, which can lead to kickback and other accidents. I recommend sharpening your chain after every few hours of use, or whenever you notice it’s not cutting as efficiently as it should.
Clean the Bar Regularly: Remove any sawdust, pitch, or debris from the bar groove and oil holes. This will ensure proper lubrication.
Check the Bar for Wear: Inspect the bar rails for wear or damage. If the rails are worn unevenly, you can flip the bar over to even out the wear. If the bar is severely damaged, it should be replaced.
Lubricate the Chain Regularly: Keep the chain oil reservoir full and use a high-quality bar and chain oil. I prefer to use a synthetic oil, as it provides better lubrication and protection, especially in cold weather.
Store the Saw Properly: When not in use, store the saw in a clean, dry place. Remove the bar and chain and clean them thoroughly before storing.

Chain Sharpening Techniques:

There are several ways to sharpen a chainsaw chain, including using a file, a grinder, or a specialized chain sharpener. Here’s a quick overview of each method:

File Sharpening: This is the most common method for sharpening chainsaws in the field. It requires a round file, a file guide, and a depth gauge tool. The file guide helps you maintain the correct filing angle and depth, while the depth gauge tool ensures that the depth gauges (the small metal tabs in front of each cutting tooth) are set to the correct height.
Grinder Sharpening: This method uses an electric grinder with a specialized grinding wheel to sharpen the chain. It’s faster and more precise than file sharpening, but it requires more equipment and skill.
Chain Sharpener: These are specialized machines that are designed to sharpen chainsaw chains quickly and accurately. They are typically used by professional chainsaw shops.

Pro Tip: No matter which method you use, always follow the manufacturer’s instructions and wear safety glasses to protect your eyes from flying debris.

Wood Types and Cutting Techniques

The type of wood you’re cutting and the cutting techniques you use can also affect the performance of your chainsaw.

Hardwoods vs. Softwoods: Hardwoods (like oak, maple, and hickory) are denser and more difficult to cut than softwoods (like pine, fir, and spruce). When cutting hardwoods, you may need to use a slower cutting speed and apply more pressure.
Green Wood vs. Dry Wood: Green wood (freshly cut wood) has a higher moisture content than dry wood, which makes it more difficult to cut. Green wood also tends to bind up the chain more easily.
Cutting Techniques: Different cutting techniques are used for different types of cuts. For example, felling a tree requires different techniques than bucking logs or limbing branches.

Data Points and Statistics:

Wood Moisture Content: The moisture content of wood is expressed as a percentage of the wood’s dry weight. Green wood can have a moisture content of over 100%, while dry firewood should have a moisture content of 20% or less.
Wood Strength: The strength of wood varies depending on the species, density, and moisture content. Hardwoods are generally stronger than softwoods.
Chainsaw Calibration: Chainsaws should be calibrated regularly to ensure proper fuel mixture and idle speed. This will help to optimize performance and extend the life of the engine.

Case Study: I once worked on a project where we were felling and bucking large oak trees for lumber. We were using Stihl MS 462 chainsaws with 25-inch bars. We quickly realized that the chains were dulling much faster than expected, due to the hardness of the oak. We switched to using carbide-tipped chains, which are more resistant to wear and can hold their edge for longer. This significantly improved our productivity and reduced the amount of time we spent sharpening chains.

Safety Considerations

Chainsaw safety is paramount. Always follow these safety guidelines when operating a chainsaw:

Wear Appropriate Safety Gear: This includes a helmet, safety glasses, hearing protection, gloves, chaps, and sturdy boots.
Inspect the Saw Before Use: Check the chain tension, oil level, and all other components to ensure they are in good working order.
Use Proper Cutting Techniques: Avoid cutting above shoulder height or reaching too far.
Be Aware of Kickback: Kickback is a sudden, uncontrolled upward movement of the chainsaw bar that can cause serious injury. Be aware of the risk of kickback and take steps to avoid it.
Never Cut Alone: Always work with a partner in case of an emergency.
Take Breaks: Chainsaw operation can be physically demanding. Take frequent breaks to avoid fatigue.

Statistics: According to the Consumer Product Safety Commission, chainsaws cause approximately 36,000 injuries each year in the United States. Most of these injuries are preventable with proper safety precautions.

Troubleshooting Common Problems

Even with proper maintenance, you may encounter problems with your chainsaw from time to time. Here are some common problems and their solutions:

Chain is dull: Sharpen the chain.
Chain is loose: Tighten the chain.
Saw is not cutting properly: Check the chain tension, chain sharpness, and bar lubrication.
Saw is difficult to start: Check the spark plug, air filter, and fuel.
Saw is smoking: Check the fuel mixture and air filter.
Saw is overheating: Check the cooling fins and air filter.

My Experience: I once had a chainsaw that was constantly overheating. I checked the cooling fins and air filter, but they were clean. I eventually discovered that the problem was a clogged exhaust port. I cleaned the exhaust port with a wire brush, and the saw started running normally again.

Conclusion

Upsizing the bar and chain on your Stihl MS 291 can be a great way to enhance its performance and tackle larger cutting tasks. However, it’s important to do your research, choose the right bar and chain, and maintain your equipment properly. By following the guidelines in this guide, you can safely and effectively upsize your chainsaw and get the most out of it. Remember, safety always comes first! Take your time, be careful, and enjoy the satisfaction of a job well done.

Stihl MS 291 Chain Size Guide: Bar & Chain Upsize Tips (Pro Hacks)