Stihl MS291 Chain Size and Overheating Fixes (Pro Woodworker Tips)
The Stihl MS291 is a workhorse. I’ve spent countless hours with mine, felling trees, bucking logs, and prepping firewood. But like any machine, it can throw you a curveball. One of the most frustrating problems I’ve encountered, and I know many others have too, is figuring out the right chain size and dealing with overheating. It’s a double whammy that can bring any wood processing project to a screeching halt. Over the years, I’ve learned a few tricks and techniques that have helped me keep my MS291 running smoothly. Let me share my experiences and insights with you, so you can avoid the same headaches.
Understanding the Stihl MS291 Chain Size
The right chain size is crucial for the MS291’s performance and longevity. Using the wrong chain can lead to poor cutting, increased wear and tear, and even damage to the saw. Here’s what you need to know.
Chain Pitch, Gauge, and Drive Links: The Holy Trinity
These three parameters define a chainsaw chain. Getting them right is non-negotiable.
- Pitch: The pitch is the distance between any three consecutive rivets on the chain, divided by two. It’s usually expressed in inches. The Stihl MS291 typically uses a 3/8″ pitch chain.
- Gauge: The gauge is the thickness of the drive links – the parts of the chain that fit into the guide bar groove. The MS291 generally uses a 0.063″ (1.6mm) gauge chain.
- Drive Links: The number of drive links is the total number of these links on the chain. This number depends on the length of the guide bar you’re using.
Why does it matter? Think of it like this: if the pitch is wrong, the chain won’t properly engage with the sprocket. If the gauge is wrong, the chain won’t fit snugly in the guide bar, leading to excessive vibration and wear. If the number of drive links is wrong, the chain will either be too loose or too tight.
My experience: I once tried to use a chain with the wrong pitch on my MS291. The saw vibrated violently, and the chain kept jumping off the bar. It was a frustrating and potentially dangerous experience. I quickly learned my lesson and now double-check the specs before buying a new chain.
Matching Chain Size to Bar Length
The MS291 can accommodate different bar lengths, typically ranging from 16″ to 20″. The longer the bar, the more drive links you’ll need. Here’s a general guideline:
Bar Length (Inches) | Chain Pitch (Inches) | Chain Gauge (Inches) | Drive Links (Approximate) |
---|---|---|---|
16″ | 3/8″ | 0.063″ | 55 |
18″ | 3/8″ | 0.063″ | 61 |
20″ | 3/8″ | 0.063″ | 66 |
Important Note: These are approximate values. Always consult your owner’s manual or the Stihl website for the exact number of drive links for your specific bar. I always count the drive links on my old chain before ordering a new one just to be absolutely sure.
A Case Study: I was working on a large oak log with a 20″ bar. I initially used a chain with 65 drive links, thinking it would be close enough. The chain was too tight, putting excessive strain on the saw. After switching to a chain with 66 drive links, the saw ran much smoother, and the cutting performance improved significantly.
Identifying the Right Chain
The easiest way to identify the right chain is to look for the stamped markings on the chain itself. These markings usually indicate the pitch, gauge, and drive link count. You can also consult your owner’s manual or use the Stihl chain selector tool on their website.
Pro Tip: I keep a small notebook in my workshop with the chain specs for all my saws. It’s a handy reference when I’m ordering parts online or at the local hardware store.
Chain Types: Ripping vs. Crosscutting
Chains come in different configurations designed for specific cutting tasks. The two main types are ripping chains and crosscutting chains.
- Crosscutting Chains: These are the most common type of chain, designed for cutting across the grain of the wood. They have a higher top plate angle (typically 60 degrees) for aggressive cutting.
- Ripping Chains: These chains are designed for cutting with the grain of the wood, such as when milling lumber. They have a lower top plate angle (typically 10 degrees) for smoother, more efficient cutting along the grain.
Which one should you use? For general firewood cutting and felling trees, a crosscutting chain is the way to go. If you’re planning to mill lumber with your MS291, you’ll need a ripping chain.
My Experience: I tried using a crosscutting chain to mill a cedar log once. The saw struggled, and the cut was rough and uneven. After switching to a ripping chain, the saw sliced through the log with ease, producing a smooth, clean cut.
Troubleshooting Overheating Issues
Overheating is a common problem with chainsaws, and the MS291 is no exception. It can lead to reduced performance, increased wear and tear, and even engine damage. Here’s a breakdown of the causes and how to fix them.
Common Causes of Overheating
- Dull Chain: A dull chain forces the saw to work harder, generating more heat.
- Improper Chain Tension: A chain that’s too tight creates excessive friction, leading to overheating.
- Insufficient Chain Lubrication: Without proper lubrication, the chain and bar will overheat quickly.
- Clogged Air Filter: A dirty air filter restricts airflow to the engine, causing it to run hot.
- Incorrect Fuel Mixture: Using the wrong fuel mixture can lead to incomplete combustion and overheating.
- Running the Saw at High RPMs for Extended Periods: Prolonged use at high RPMs can generate excessive heat.
- Cutting Hardwoods: Hardwoods like oak and maple require more power to cut, which can cause the saw to overheat faster than when cutting softwoods like pine.
Diagnosing Overheating
- Listen to the Engine: An overheating engine will often sound strained or labored.
- Check the Bar and Chain: If the bar and chain are excessively hot to the touch, the saw is likely overheating.
- Look for Smoke: Smoke coming from the engine or bar is a clear sign of overheating.
- Feel for Loss of Power: An overheating saw will often lose power and struggle to cut.
Fixing Overheating: A Step-by-Step Guide
-
Sharpen the Chain: A sharp chain is the first line of defense against overheating. I recommend sharpening your chain every time you refuel. Use a chainsaw file or a sharpening jig to maintain the correct cutting angles.
- Filing Technique: Maintain a consistent angle and pressure as you file each tooth. File from the inside out, following the existing angle of the cutting edge.
- Depth Gauge Adjustment: Use a depth gauge tool to ensure that the depth gauges (the small metal tabs in front of each cutting tooth) are set to the correct height. Too high, and the chain won’t cut effectively. Too low, and the chain will grab and chatter. I usually set mine to 0.025″ for general purpose cutting.
-
Adjust Chain Tension: Proper chain tension is crucial. The chain should be snug against the bar but still able to be pulled around by hand.
- Tensioning Procedure: Loosen the bar nuts, then use the tensioning screw to adjust the chain tension. Tighten the bar nuts securely after adjusting the tension. The chain should snap back against the bar when pulled away slightly.
- Checking Tension: Check the tension frequently, especially when the chain is new. New chains tend to stretch quickly. I usually check mine after every few cuts.
-
Ensure Proper Chain Lubrication: Use a high-quality bar and chain oil. Check the oil level frequently and refill as needed.
- Oil Type: I prefer using a vegetable-based bar and chain oil. It’s more environmentally friendly and provides excellent lubrication.
- Oil Flow Adjustment: The MS291 has an adjustable oiler. Make sure it’s set to deliver enough oil for the cutting conditions. I usually increase the oil flow when cutting hardwoods or in hot weather. To check the oiler, start the saw and hold it over a piece of cardboard. You should see a steady stream of oil coming from the bar.
-
Clean the Air Filter: A dirty air filter restricts airflow to the engine, causing it to run hot. Clean the air filter regularly with compressed air or warm, soapy water.
- Cleaning Procedure: Remove the air filter cover and carefully remove the filter. Tap the filter gently to remove loose debris. If the filter is heavily soiled, wash it with warm, soapy water. Rinse thoroughly and allow it to dry completely before reinstalling.
- Filter Inspection: Inspect the air filter for damage. Replace it if it’s torn or cracked. I usually replace mine every year, regardless of its condition.
-
Use the Correct Fuel Mixture: The MS291 requires a 50:1 fuel-to-oil ratio. Use a high-quality two-stroke oil and mix it thoroughly with fresh gasoline.
- Mixing Procedure: Use a calibrated mixing container to ensure the correct ratio. Pour the oil into the container first, then add the gasoline. Shake the container vigorously to mix the fuel thoroughly.
- Fuel Storage: Store fuel in an approved container in a cool, dry place. Use fuel within 30 days for optimal performance. Old fuel can degrade and cause engine problems. I always add a fuel stabilizer to my gasoline to extend its shelf life.
-
Avoid Prolonged High RPM Operation: Give the saw a break every 15-20 minutes to allow it to cool down.
- Cooling Breaks: During breaks, turn off the saw and allow it to idle for a few minutes before shutting it down completely. This helps dissipate heat from the engine.
- Cutting Technique: Avoid forcing the saw. Let the chain do the work. Forcing the saw will only generate more heat and increase the risk of kickback.
-
Consider Wood Type: Cutting hardwoods generates more heat than softwoods. Take more frequent breaks when cutting hardwoods.
- Wood Density: Hardwoods are denser than softwoods, meaning they require more energy to cut. This increased energy translates to increased heat. Oak, maple, and hickory are examples of hardwoods. Pine, fir, and cedar are examples of softwoods.
- Cutting Strategy: When cutting hardwoods, use a sharp chain and avoid pushing down on the saw. Let the weight of the saw do the work. Take smaller bites and allow the saw to cool down frequently.
Dealing with Resin Buildup
Resin buildup on the bar and chain can also contribute to overheating. Clean the bar and chain regularly with a solvent designed for removing resin.
- Cleaning Procedure: Remove the bar and chain from the saw. Use a scraper or wire brush to remove as much resin as possible. Soak the bar and chain in a solvent for a few minutes, then scrub them with a brush. Rinse with clean water and allow them to dry completely before reinstalling.
- Solvent Choice: I use a citrus-based solvent for removing resin. It’s effective and environmentally friendly. Avoid using harsh chemicals like gasoline or kerosene, as they can damage the bar and chain.
When to Seek Professional Help
If you’ve tried all of the above and your MS291 is still overheating, it’s time to take it to a qualified mechanic. There may be an underlying problem with the engine that requires professional attention.
- Common Engine Problems: Common engine problems that can cause overheating include a faulty carburetor, a clogged exhaust port, or a damaged cylinder.
- Preventive Maintenance: Regular maintenance is key to preventing engine problems. I recommend having your saw serviced by a qualified mechanic at least once a year.
Optimizing Performance for Firewood Preparation
Preparing firewood efficiently requires a combination of technique, sharp tools, and a well-maintained chainsaw.
Wood Selection Criteria
The type of wood you choose for firewood will affect its burning characteristics and heat output.
- Hardwoods vs. Softwoods: Hardwoods like oak, maple, and ash are denser and burn longer than softwoods like pine, fir, and cedar. Hardwoods also produce more heat per cord.
-
Moisture Content: The moisture content of the wood is critical. Green wood (freshly cut) has a high moisture content and is difficult to burn. It also produces a lot of smoke and creosote. Seasoned wood (dried) has a low moisture content and burns cleanly and efficiently.
- Ideal Moisture Content: The ideal moisture content for firewood is between 15% and 20%. You can measure the moisture content using a moisture meter.
- Drying Time: The drying time for firewood depends on the type of wood, the climate, and how the wood is stacked. Generally, hardwoods take longer to dry than softwoods. In a dry climate, firewood can be seasoned in as little as six months. In a humid climate, it may take a year or more. I usually let my firewood season for at least a year before burning it.
Safe Wood Stacking Practices
Properly stacking firewood is essential for efficient drying and preventing rot.
- Elevate the Wood: Stack the wood on pallets or other supports to keep it off the ground. This allows air to circulate underneath the pile, promoting drying.
- Stack Loosely: Leave space between the logs to allow air to circulate.
- Cover the Top: Cover the top of the pile with a tarp to protect the wood from rain and snow. Leave the sides open to allow air to circulate.
- Location: Stack the wood in a sunny, well-ventilated location.
Efficient Cutting Techniques
-
Bucking Logs: Bucking is the process of cutting logs into shorter lengths. Use a sawbuck or other support to hold the logs securely while you cut them.
- Sawbuck Design: A sawbuck is a simple wooden frame that holds logs at a comfortable height for cutting. You can build your own sawbuck using readily available materials. I built mine out of scrap lumber and it has served me well for years.
- Cutting Lengths: Cut the logs to the desired length for your fireplace or wood stove. I usually cut mine to 16″ lengths.
-
Splitting Wood: Splitting wood makes it easier to dry and burn. Use a maul or splitting axe to split the logs.
- Splitting Technique: Place the log on a chopping block. Position the maul or axe on the log and swing with a controlled motion. Aim for the center of the log.
- Safety Precautions: Wear safety glasses and gloves when splitting wood. Keep your feet clear of the splitting area.
Safety Equipment Requirements
Safety is paramount when working with chainsaws and firewood.
-
Personal Protective Equipment (PPE):
- Safety Glasses: Protect your eyes from flying debris.
- Hearing Protection: Chainsaws are loud. Wear earplugs or earmuffs to protect your hearing.
- Gloves: Protect your hands from cuts and abrasions.
- Chainsaw Chaps: Protect your legs from chainsaw cuts.
- Steel-Toed Boots: Protect your feet from falling logs.
- Helmet: Protect your head from falling branches.
-
Chainsaw Maintenance: Keep your chainsaw in good working order. Sharpen the chain regularly, check the oil level, and clean the air filter.
-
Safe Cutting Practices:
- Kickback Awareness: Be aware of the risk of kickback. Kickback occurs when the tip of the chainsaw bar contacts a solid object, causing the saw to jump back towards the operator.
- Proper Stance: Maintain a stable stance with your feet shoulder-width apart. Keep your weight balanced.
- Grip: Grip the saw firmly with both hands. Keep your thumbs wrapped around the handles.
- Clear Cutting Area: Clear the cutting area of obstacles.
Industry Standards and Forestry Regulations
Be aware of any industry standards or forestry regulations that may apply to your firewood preparation activities.
- Firewood Permits: Some areas require permits for cutting firewood on public lands. Check with your local forestry agency for more information.
- Invasive Species: Be aware of the risk of spreading invasive species through firewood. Don’t transport firewood long distances. Buy firewood locally.
- Best Management Practices (BMPs): Follow best management practices for sustainable forestry. These practices help protect water quality, wildlife habitat, and soil health.
Data Points and Statistics
- Wood Strength: The compressive strength of wood varies depending on the species. Oak has a compressive strength of around 7,000 psi, while pine has a compressive strength of around 4,000 psi.
- Drying Tolerances: Wood shrinks as it dries. The amount of shrinkage varies depending on the species and the drying conditions. Generally, wood shrinks about 1% for every 4% reduction in moisture content.
- Tool Performance Metrics: Chainsaw chain speed is typically measured in feet per second (fps). A sharp chain on a well-maintained MS291 can achieve a chain speed of up to 80 fps.
- Industry Standards: The American National Standards Institute (ANSI) sets standards for chainsaw safety. These standards cover topics such as kickback reduction and operator training.
Original Research and Case Studies
I conducted a small-scale study to compare the performance of different chainsaw chains on the MS291. I tested three different chains: a standard crosscutting chain, a ripping chain, and a low-kickback chain. I measured the cutting speed, fuel consumption, and vibration levels for each chain.