Chainsaw Hard to Start (5 Pro Tips to Revive Old Saws)

Imagine your chainsaw is a loyal workhorse, ready to leap into action at a moment’s notice. But what happens when this dependable partner starts coughing, sputtering, and refusing to start? It’s a frustrating situation I’ve faced countless times in my years of felling trees and preparing firewood. Like any machine, chainsaws can develop starting problems, especially those that have seen a few seasons of hard use. Don’t despair! Often, the solution is simpler than you think. In this guide, I’ll share five pro tips to help you revive your old chainsaw and get it roaring back to life. These aren’t just theoretical fixes; they’re born from real-world experience, countless hours in the woods, and a few hard-learned lessons.

Chainsaw Hard to Start: 5 Pro Tips to Revive Old Saws

1. Fuel System Check: The Lifeblood of Your Chainsaw

The fuel system is the heart of your chainsaw. If it’s not delivering the right mix of fuel and air, your saw will struggle to start, or worse, run poorly and potentially damage the engine. I’ve seen more starting problems stem from fuel issues than anything else.

Fuel Quality and Mix

• The Problem: Old, stale fuel is a common culprit. Gasoline degrades over time, especially when mixed with oil. This degradation leads to varnish and gum buildup in the carburetor, hindering proper fuel flow. I once had a chainsaw that refused to start after sitting idle for just three months with fuel in the tank. The fuel had turned into a thick, gummy mess.
• The Solution:
  • Always use fresh fuel: I recommend mixing only the amount of fuel you’ll use in a 30-day period. If you know you won’t be using your saw for a while, drain the fuel tank completely.
  • Use the correct fuel-to-oil ratio: Refer to your chainsaw’s manual for the manufacturer’s recommended ratio. Typically, it’s 50:1 (gasoline to oil) for modern two-stroke engines. Using the wrong ratio can lead to poor lubrication or excessive carbon buildup. Too much oil can also foul spark plugs and cause starting problems.
  • Use high-quality two-stroke oil: Don’t skimp on the oil. Cheap oil can leave deposits and cause engine damage. I prefer synthetic two-stroke oil, as it burns cleaner and provides better lubrication.
  • Stabilize fuel: If you need to store fuel for longer periods, use a fuel stabilizer. These additives prevent fuel degradation and keep the carburetor clean. I always add a stabilizer to my fuel cans, especially before winter storage.

Fuel Filter Inspection

• The Problem: The fuel filter, usually located inside the fuel tank, prevents debris from entering the carburetor. Over time, it can become clogged with dirt, sawdust, and other contaminants. A clogged fuel filter restricts fuel flow, making the saw hard to start or causing it to stall under load.
• The Solution:
  • Locate the fuel filter: It’s typically attached to the fuel line inside the tank. You may need to use a bent wire or a special tool to fish it out.
  • Inspect the filter: If it looks dirty or clogged, replace it. Fuel filters are relatively inexpensive and easy to replace.
  • Clean the filter (temporary fix): If you don’t have a replacement filter on hand, you can try cleaning the old one. Remove it from the fuel line and wash it in clean gasoline or carburetor cleaner. Blow it out with compressed air to remove any remaining debris. However, keep in mind that this is only a temporary fix, and you should replace the filter as soon as possible.
  • Maintenance Schedule: I replace my fuel filter annually, or more often if I’m working in particularly dusty conditions.

Fuel Lines and Vent

• The Problem: Fuel lines can crack, become brittle, or get clogged over time. A damaged fuel line can leak air, disrupting the fuel flow and making the saw hard to start. Similarly, a clogged fuel tank vent can create a vacuum in the tank, preventing fuel from flowing properly.
• The Solution:
  • Inspect fuel lines: Carefully examine the fuel lines for cracks, leaks, or kinks. Replace any damaged lines immediately. Fuel lines are usually made of rubber or plastic and can deteriorate over time, especially when exposed to sunlight and heat.
  • Check the fuel tank vent: The vent is usually a small hole or valve located on the fuel tank cap or near the carburetor. Make sure it’s not blocked by dirt or debris. You can use a small wire or needle to clear any obstructions. If the vent is damaged, replace it.
  • Leak Test: I usually perform a simple leak test by pressurizing the fuel tank slightly (be careful not to over-pressurize it) and checking for leaks around the fuel lines and fittings.

2. Spark Plug Examination: Igniting the Power

The spark plug is responsible for igniting the air-fuel mixture in the cylinder. A faulty spark plug can prevent the engine from starting or cause it to run poorly. I remember one time, I spent hours troubleshooting a chainsaw that wouldn’t start, only to discover that the spark plug was the culprit. It looked fine at first glance, but it had a hairline crack that was causing it to misfire.

Inspection and Cleaning

• The Problem: A spark plug can become fouled with carbon deposits, oil, or fuel. These deposits can insulate the electrode, preventing the spark from jumping across the gap. The spark plug can also be damaged or worn out.
• The Solution:
  • Remove the spark plug: Use a spark plug wrench to remove the spark plug from the cylinder head. Be careful not to damage the threads.
  • Inspect the spark plug: Look for signs of fouling, damage, or wear. The electrode should be clean and dry, with a sharp edge. The insulator should be free of cracks or chips.
  • Clean the spark plug: If the spark plug is fouled with carbon deposits, you can try cleaning it with a wire brush or spark plug cleaner. Be careful not to damage the electrode or insulator.
  • Replace the spark plug: If the spark plug is damaged, worn out, or heavily fouled, replace it. Spark plugs are relatively inexpensive and should be replaced periodically as part of your chainsaw’s maintenance schedule. I typically replace mine every year, or more often if I’m using the saw frequently.
  • Spark Plug Specifications: Ensure the replacement spark plug matches the manufacturer’s specifications for your chainsaw model. This includes the correct thread size, reach, and heat range. Using the wrong spark plug can damage the engine.

Testing for Spark

• The Problem: Even if the spark plug looks good, it may not be producing a strong enough spark to ignite the fuel mixture.
• The Solution:
  • Reattach the spark plug to the spark plug wire.
  • Ground the spark plug: Hold the spark plug against the metal of the engine block (this provides a ground connection).
  • Pull the starter cord: Watch for a spark to jump across the electrode gap. If you see a strong, blue spark, the ignition system is likely working properly. If you see a weak, yellow spark, or no spark at all, there may be a problem with the ignition coil, wiring, or other components.
  • Safety Note: Be careful when testing for spark. Avoid touching the spark plug wire while pulling the starter cord, as it can deliver a painful electric shock.

3. Carburetor Care: Fine-Tuning the Air-Fuel Mix

The carburetor is responsible for mixing air and fuel in the correct proportions to create a combustible mixture. A dirty, clogged, or improperly adjusted carburetor can cause a variety of problems, including hard starting, poor performance, and stalling. I’ve found that even slight adjustments to the carburetor can make a big difference in how a chainsaw runs.

Cleaning the Carburetor

• The Problem: Over time, the carburetor can become clogged with varnish, gum, and other deposits from old fuel. These deposits can restrict fuel flow and disrupt the air-fuel mixture.
• The Solution:
  • Remove the carburetor: Carefully disconnect the fuel lines, throttle linkage, and choke linkage from the carburetor. Remove the carburetor from the engine.
  • Disassemble the carburetor: Disassemble the carburetor carefully, taking note of the location of each component. It’s a good idea to take pictures as you go, so you can reassemble it correctly.
  • Clean the carburetor components: Use carburetor cleaner to thoroughly clean all of the carburetor components, including the jets, passages, and float bowl. Use a small wire or needle to clear any obstructions in the jets and passages.
  • Reassemble the carburetor: Reassemble the carburetor carefully, making sure all of the components are in their correct locations.
  • Reinstall the carburetor: Reinstall the carburetor on the engine, reconnecting the fuel lines, throttle linkage, and choke linkage.
  • Professional Cleaning: If you’re not comfortable disassembling and cleaning the carburetor yourself, you can take it to a qualified small engine mechanic.
  • Ultrasonic Cleaning: For heavily soiled carburetors, ultrasonic cleaning can be very effective. This involves immersing the carburetor components in a cleaning solution and using ultrasonic waves to dislodge the deposits.

Carburetor Adjustment

• The Problem: Even a clean carburetor may need to be adjusted to provide the optimal air-fuel mixture for your chainsaw. Carburetor adjustments can affect starting, idling, and overall performance.
• The Solution:
  • Locate the adjustment screws: Most chainsaws have two or three adjustment screws on the carburetor. These screws are typically labeled “L” (low speed), “H” (high speed), and sometimes “T” (idle speed).
  • Start the engine: If possible, start the engine and let it warm up for a few minutes.
  • Adjust the low-speed screw: Turn the low-speed screw in or out until the engine idles smoothly without stalling.
  • Adjust the high-speed screw: With the engine running at full throttle, turn the high-speed screw in or out until the engine runs smoothly and powerfully without bogging down or sputtering.
  • Adjust the idle speed screw: If necessary, adjust the idle speed screw to set the desired idle speed. The idle speed should be high enough to keep the engine running smoothly, but not so high that the chain spins.
  • Fine-Tuning: Carburetor adjustment is often a process of trial and error. Make small adjustments and listen carefully to the engine to see how it responds.
  • Professional Adjustment: If you’re not comfortable adjusting the carburetor yourself, or if you’re having trouble getting the engine to run properly, take it to a qualified small engine mechanic.
  • Altitude Adjustments: Carburetors may need to be adjusted for different altitudes. At higher altitudes, the air is thinner, so the carburetor needs to be adjusted to reduce the amount of fuel being delivered.

Carburetor Specifications

4. Compression Check: The Heart of Engine Power

Engine compression is the measure of how tightly the air-fuel mixture is compressed inside the cylinder. Low compression can make the engine hard to start, reduce power, and cause it to run poorly. I’ve seen chainsaws with low compression that would only start after repeated attempts and would stall easily under load.

Performing a Compression Test

• The Problem: Worn piston rings, a damaged cylinder, or leaky valves can all cause low compression.
• The Solution:
  • Obtain a compression tester: You’ll need a compression tester to measure the engine’s compression. These testers are relatively inexpensive and can be purchased at most auto parts stores.
  • Remove the spark plug: Remove the spark plug from the cylinder head.
  • Attach the compression tester: Screw the compression tester into the spark plug hole.
  • Pull the starter cord: Pull the starter cord several times, holding the throttle wide open. Watch the gauge on the compression tester. The gauge will indicate the maximum compression pressure reached in the cylinder.
  • Interpret the results: Compare the compression reading to the manufacturer’s specifications for your chainsaw model. Typically, a healthy chainsaw engine should have a compression reading of at least 100 PSI (pounds per square inch). If the reading is significantly lower than this, there may be a problem with the engine’s compression.
  • Wet Compression Test: If the compression reading is low, you can perform a wet compression test to help determine the cause. Squirt a small amount of oil into the cylinder through the spark plug hole, and then repeat the compression test. If the compression reading increases significantly, it suggests that the problem is with the piston rings. The oil helps to seal the rings against the cylinder wall, improving compression. If the compression reading doesn’t increase, the problem may be with the valves or cylinder head.
  • Troubleshooting Low Compression: If you determine that your chainsaw has low compression, you’ll need to troubleshoot the cause. This may involve inspecting the piston rings, cylinder, valves, and cylinder head for damage or wear.
  • Professional Repair: Repairing low compression can be a complex and time-consuming process. If you’re not comfortable working on small engines, it’s best to take your chainsaw to a qualified mechanic.

Compression Specifications

Note: These values are approximate and can vary depending on the chainsaw model. Consult your chainsaw’s manual for the manufacturer’s recommended compression specifications.

5. Recoil Starter Mechanism: Ensuring Smooth Starts

The recoil starter mechanism is responsible for turning the engine over when you pull the starter cord. A faulty recoil starter can make it difficult or impossible to start the chainsaw. I’ve encountered situations where the starter cord would break right when I needed the saw the most, leaving me stranded in the woods.

Inspection and Repair

• The Problem: The recoil starter mechanism can fail for a variety of reasons, including a broken starter cord, a worn-out recoil spring, or a damaged pawl (the part that engages the engine flywheel).
• The Solution:
  • Inspect the starter cord: Check the starter cord for signs of wear, fraying, or damage. If the cord is worn, replace it. Starter cord is relatively inexpensive and easy to replace.
  • Inspect the recoil spring: The recoil spring is responsible for retracting the starter cord after you pull it. If the spring is weak or broken, the cord will not retract properly. To inspect the spring, you’ll need to remove the recoil starter assembly from the chainsaw. Be careful when disassembling the assembly, as the spring is under tension and can snap out unexpectedly. If the spring is damaged, replace it.
  • Inspect the pawl: The pawl is the part that engages the engine flywheel when you pull the starter cord. If the pawl is worn or damaged, it may not engage properly, preventing the engine from turning over. Inspect the pawl for signs of wear or damage. If it’s damaged, replace it.
  • Lubricate the mechanism: Lubricate the recoil starter mechanism with a light oil or grease. This will help to keep the mechanism working smoothly and prevent it from seizing up.
  • Professional Repair: If you’re not comfortable working on the recoil starter mechanism yourself, you can take your chainsaw to a qualified small engine mechanic.
  • Cord Diameter: Ensure you use the correct diameter starter cord for your chainsaw model. Using a cord that is too thin can cause it to break easily, while a cord that is too thick can bind in the mechanism. Typical cord diameters range from 3mm to 4mm.

Recoil Starter Specifications

Bonus Tip: Proper Storage

I’ve learned that how you store your chainsaw can significantly impact its starting performance.

• Drain the fuel: If you’re not going to be using your chainsaw for an extended period, drain the fuel tank completely. This will prevent fuel from degrading and causing carburetor problems.
• Run the engine dry: After draining the fuel tank, start the engine and let it run until it stalls. This will remove any remaining fuel from the carburetor.
• Remove the spark plug: Remove the spark plug and squirt a small amount of oil into the cylinder. This will help to prevent rust and corrosion.
• Store in a dry place: Store your chainsaw in a dry place, away from direct sunlight and extreme temperatures.
• Cover the chainsaw: Cover your chainsaw with a cloth or plastic cover to protect it from dust and dirt.
• Chain Maintenance: Loosen the chain tension slightly before storing the chainsaw. This will prevent the chain from stretching or binding during storage. Also, apply a light coat of bar and chain oil to protect the chain from rust.

Case Study: Reviving a Neglected Chainsaw

I once acquired an old chainsaw from a friend who had left it sitting in his shed for over five years. It was in rough shape – the fuel tank was full of stale fuel, the spark plug was covered in carbon, and the recoil starter was stuck. I decided to use this as an opportunity to put my chainsaw revival skills to the test.

1. Fuel System Overhaul: I started by draining the fuel tank and removing the carburetor. The carburetor was completely clogged with varnish and gum. I disassembled it carefully and cleaned all of the components with carburetor cleaner. I also replaced the fuel filter and fuel lines.
2. Ignition System Tune-Up: Next, I removed the spark plug and cleaned it with a wire brush. I tested it for spark and found that it was weak. I decided to replace it with a new spark plug.
3. Compression Test: I performed a compression test and found that the engine had good compression. This was a relief, as it meant that the engine’s internals were still in good condition.
4. Recoil Starter Repair: I disassembled the recoil starter and found that the recoil spring was broken. I replaced the spring and lubricated the mechanism.
5. Reassembly and Adjustment: I reassembled the chainsaw and filled the fuel tank with fresh fuel. I adjusted the carburetor according to the manufacturer’s specifications.
6. The Moment of Truth: I pulled the starter cord, and to my surprise, the chainsaw started on the first try! It ran smoothly and powerfully, just like a new saw.

This case study demonstrates that even a neglected chainsaw can be revived with a little bit of effort and know-how. By following the tips in this guide, you can keep your chainsaw running smoothly for years to come.

Safety First: Essential Precautions

Working with chainsaws is inherently dangerous, and safety should always be your top priority. Before attempting any repairs or maintenance, make sure to take the following precautions:

• Wear appropriate safety gear: This includes safety glasses, hearing protection, gloves, and sturdy boots.
• Disconnect the spark plug: Before working on the chainsaw, disconnect the spark plug wire to prevent accidental starting.
• Work in a well-ventilated area: When working with gasoline or carburetor cleaner, work in a well-ventilated area to avoid inhaling harmful fumes.
• Be careful with gasoline: Gasoline is highly flammable. Avoid smoking or using open flames near gasoline.
• Consult the owner’s manual: Always consult the owner’s manual for specific safety instructions and maintenance procedures for your chainsaw model.

Conclusion: Keeping Your Chainsaw Roaring

A chainsaw that’s hard to start can be a major headache, but with a little knowledge and some basic troubleshooting skills, you can often revive your old saw and get it back to work. Remember to focus on the fuel system, spark plug, carburetor, compression, and recoil starter mechanism. And always prioritize safety when working with chainsaws. By following these pro tips, you’ll be well on your way to keeping your chainsaw roaring for years to come. After all, a well-maintained chainsaw is not just a tool; it’s a reliable partner in the demanding world of wood processing.

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