Start 260 Troubleshooting Tips (5 Pro Fixes for Hard Starts)

Why did the chainsaw break up with the log? Because it said, “I’m board!”

Alright, jokes aside (though a little levity never hurt anyone wrestling with a stubborn chainsaw), let’s dive into the frustrating world of a hard-starting Stihl MS 260. I know the feeling. You’re ready to tackle that pile of wood, the air smells crisp, and then… nothing. Just the disheartening pull of the starter cord and the gnawing suspicion that something’s amiss.

I’ve spent countless hours in the woods, from the dense forests of the Pacific Northwest to the sun-drenched eucalyptus groves of California, and the MS 260 has been a trusty companion. But even the best tools have their quirks. Over the years, I’ve learned a thing or two about diagnosing and fixing hard starting issues on this particular saw. Forget generic advice; this is about the MS 260 specifically.

This guide isn’t just a collection of troubleshooting steps; it’s a distillation of my experience, blended with technical knowledge and a healthy dose of practical wisdom. I’ll walk you through the most common culprits, from simple fixes to more involved repairs, all with the goal of getting your MS 260 roaring back to life. We will cover these pro fixes for hard starts:

• Fuel System Check-Up: Ensuring your fuel is fresh, the filter is clean, and the carburetor is properly adjusted.
• Ignition System Inspection: Verifying the spark plug is firing correctly and the ignition module is functioning.
• Compression Test: Checking the engine’s compression to rule out serious mechanical issues.
• Air Intake Analysis: Making sure the air filter is clean and the intake is unobstructed.
• Exhaust System Evaluation: Confirming the exhaust port and muffler are clear of carbon buildup.

Understanding the Stihl MS 260: A Brief Overview

Before we get our hands dirty, let’s level-set on the MS 260. This saw is renowned for its balance of power and weight, making it a favorite among both professionals and serious homeowners. It typically features a 50cc engine, delivering around 3.2 horsepower. It’s a workhorse, plain and simple.

Technical Specifications (Typical):

• Engine Displacement: 50.2 cc (3.06 cu in)
• Power Output: 2.4 kW (3.2 bhp)
• Weight (Powerhead): 4.8 kg (10.6 lbs)
• Fuel Tank Capacity: 0.51 l (17.3 oz)
• Oil Tank Capacity: 0.27 l (9.1 oz)
• Guide Bar Length (Recommended): 16-20 inches

These specs matter because they give us a baseline for performance. A hard-starting MS 260 is often a sign that one or more of these systems isn’t functioning within its optimal range.

Fuel System Check-Up: The First Line of Defense

Nine times out of ten, a hard starting issue boils down to the fuel system. Fuel is the lifeblood of any combustion engine, and the MS 260 is no exception.

1. Fresh Fuel is Key

This might sound obvious, but stale fuel is a notorious culprit. Gasoline degrades over time, especially when mixed with oil (which is necessary for a 2-stroke engine).

Personal Story: I once spent an entire afternoon tearing apart a carburetor, convinced it was the problem, only to discover the fuel I was using was over six months old. Lesson learned: always start with fresh fuel.

Technical Details:

• Fuel Type: Use a high-quality gasoline with an octane rating of 89 or higher.
• Oil Mixture: Stihl recommends a 50:1 fuel-to-oil ratio when using their high-quality 2-stroke oil. I’ve found this ratio to be reliable. Some users successfully use 40:1, but I prefer to stick to the manufacturer’s recommendation.
• Storage Life: Gasoline mixed with oil typically lasts about 30 days before it starts to degrade noticeably. After that, it can form gums and varnishes that clog the fuel system.
• Ethanol Content: Modern gasoline often contains ethanol, which can absorb water and cause corrosion. If possible, use ethanol-free gasoline, especially for long-term storage.

Actionable Steps:

1. Drain the old fuel: Discard any fuel that’s been sitting in the tank for more than a month.
2. Mix fresh fuel: Use a clean fuel can and accurately measure the oil and gasoline. I use a graduated cylinder for precise measurements.
3. Stabilize the fuel: If you plan to store the saw for an extended period, add a fuel stabilizer to the fresh fuel mixture. Stihl sells their own fuel stabilizer, but other brands like STA-BIL also work well.

2. Fuel Filter Inspection and Replacement

The fuel filter prevents debris from entering the carburetor. A clogged filter restricts fuel flow, leading to hard starts and poor performance.

Technical Details:

• Filter Location: The fuel filter is typically located inside the fuel tank, attached to the end of the fuel line.
• Filter Type: Most MS 260s use a small, cylindrical filter made of felt or plastic mesh.
• Replacement Interval: I recommend replacing the fuel filter at least once a year, or more frequently if you notice signs of clogging.

Actionable Steps:

1. Access the fuel filter: Use a clean piece of wire or a bent coat hanger to fish the fuel filter out of the tank through the fuel filler neck. Be careful not to damage the fuel line.
2. Inspect the filter: Examine the filter for dirt, debris, or discoloration. If it looks dirty, replace it.
3. Replace the filter: Disconnect the old filter from the fuel line and connect the new filter. Make sure the filter is securely attached.
4. Reinstall the filter: Carefully lower the filter back into the tank.

3. Carburetor Cleaning and Adjustment

The carburetor is responsible for mixing air and fuel in the correct proportions for combustion. A dirty or misadjusted carburetor can cause a variety of problems, including hard starting, stalling, and poor performance.

Technical Details:

• Carburetor Type: The MS 260 typically uses a Walbro or Zama carburetor.
• Adjustment Screws: The carburetor has three adjustment screws:
  • L (Low Speed): Controls the fuel mixture at idle and low speeds.
  • H (High Speed): Controls the fuel mixture at high speeds.
  • LA (Idle Speed): Controls the engine’s idle speed.
• Factory Settings: The factory settings for the adjustment screws are typically listed in the owner’s manual. However, these settings may need to be adjusted based on your altitude and climate.

Caution: Carburetor adjustments can be tricky. If you’re not comfortable working on carburetors, it’s best to take the saw to a qualified technician.

Actionable Steps (Basic Cleaning):

1. Remove the air filter: This will expose the carburetor.
2. Spray carburetor cleaner: Use a carburetor cleaner to spray the outside of the carburetor, paying particular attention to the throttle plate and choke.
3. Start the engine: Try to start the engine. If it starts, let it run for a few minutes to allow the carburetor cleaner to work its way through the system.
4. Adjust the idle speed: If the engine idles too fast or too slow, adjust the LA screw until the engine idles smoothly without stalling.

Actionable Steps (Deeper Cleaning – Use with Caution):

1. Remove the carburetor: Disconnect the fuel lines and throttle linkage from the carburetor.
2. Disassemble the carburetor: Carefully disassemble the carburetor, taking note of the location of all the parts.
3. Clean the parts: Use carburetor cleaner and compressed air to clean all the carburetor parts, including the jets, passages, and needle valve.
4. Reassemble the carburetor: Reassemble the carburetor, making sure all the parts are in their proper locations.
5. Reinstall the carburetor: Reconnect the fuel lines and throttle linkage to the carburetor.
6. Adjust the carburetor: Adjust the L and H screws according to the factory settings or your own experience.

Carburetor Adjustment Tips:

• Start with the factory settings: Use the factory settings as a starting point and then fine-tune the adjustments based on how the engine runs.
• Adjust the L screw first: Adjust the L screw until the engine idles smoothly and responds quickly to throttle inputs.
• Adjust the H screw second: Adjust the H screw until the engine runs smoothly at full throttle without sputtering or bogging down.
• Make small adjustments: Make small adjustments to the screws and then test the engine. It’s better to make several small adjustments than one large adjustment.
• Listen to the engine: Pay attention to how the engine sounds. A properly adjusted engine will sound smooth and powerful.

Ignition System Inspection: Sparking the Flame

If the fuel system is in good shape, the next thing to check is the ignition system. The ignition system is responsible for generating the spark that ignites the air-fuel mixture in the cylinder.

1. Spark Plug Inspection and Replacement

The spark plug is a critical component of the ignition system. A fouled or worn spark plug can prevent the engine from starting.

Technical Details:

• Spark Plug Type: The MS 260 typically uses a Bosch WSR 6 F or NGK BPMR6A spark plug.
• Spark Plug Gap: The spark plug gap should be 0.5 mm (0.020 inches).
• Replacement Interval: I recommend replacing the spark plug at least once a year, or more frequently if you notice signs of fouling or wear.

Actionable Steps:

1. Remove the spark plug: Use a spark plug wrench to remove the spark plug from the cylinder head.
2. Inspect the spark plug: Examine the spark plug for signs of fouling, wear, or damage.
   • Fouled spark plug: A fouled spark plug will be covered in carbon deposits or oil. This can be caused by a rich fuel mixture, a worn engine, or a faulty ignition system.
   • Worn spark plug: A worn spark plug will have rounded electrodes and a wider gap than specified.
   • Damaged spark plug: A damaged spark plug may have a cracked insulator or broken electrode.
3. Clean the spark plug (optional): If the spark plug is only slightly fouled, you can try cleaning it with a wire brush or spark plug cleaner. However, it’s generally best to replace the spark plug.
4. Set the spark plug gap: Use a spark plug gap tool to set the spark plug gap to 0.5 mm (0.020 inches).
5. Install the spark plug: Install the spark plug into the cylinder head and tighten it to the specified torque.

2. Ignition Module Testing

The ignition module is responsible for generating the high-voltage pulse that fires the spark plug. A faulty ignition module can prevent the engine from starting.

Technical Details:

• Ignition Module Type: The MS 260 uses a solid-state ignition module.
• Testing Method: The ignition module can be tested using a multimeter or a spark tester.

Caution: Testing the ignition module can be dangerous. If you’re not comfortable working with electrical components, it’s best to take the saw to a qualified technician.

Actionable Steps (Using a Spark Tester):

1. Disconnect the spark plug wire: Disconnect the spark plug wire from the spark plug.
2. Connect the spark tester: Connect the spark tester between the spark plug wire and the spark plug.
3. Pull the starter cord: Pull the starter cord and observe the spark tester. If the ignition module is working properly, the spark tester will produce a bright, blue spark. If there is no spark, or if the spark is weak or yellow, the ignition module may be faulty.

Actionable Steps (Using a Multimeter – Requires More Technical Skill):

1. Disconnect the ignition module: Disconnect the ignition module from the wiring harness.
2. Set the multimeter: Set the multimeter to measure resistance (ohms).
3. Measure the resistance: Measure the resistance between the ignition module’s terminals. The resistance values should be within the range specified in the service manual. If the resistance values are outside the specified range, the ignition module may be faulty.

If the ignition module is faulty, it must be replaced.

3. Checking the Flywheel Key

The flywheel key is a small, crescent-shaped piece of metal that aligns the flywheel with the crankshaft. If the flywheel key is sheared, the timing of the ignition system will be off, which can cause hard starting or no starting.

Technical Details:

• Flywheel Key Location: The flywheel key is located on the crankshaft, behind the flywheel.
• Inspection Method: The flywheel key can be inspected by removing the flywheel.

Actionable Steps:

1. Remove the spark plug: This will make it easier to turn the engine over.
2. Remove the starter assembly: Remove the starter assembly from the engine.
3. Remove the flywheel nut: Use a socket wrench to remove the flywheel nut.
4. Remove the flywheel: Use a flywheel puller to remove the flywheel from the crankshaft. Be careful not to damage the flywheel or the crankshaft.
5. Inspect the flywheel key: Examine the flywheel key for signs of shearing. If the flywheel key is sheared, it must be replaced.
6. Reinstall the flywheel: Reinstall the flywheel onto the crankshaft, aligning the keyway in the flywheel with the key on the crankshaft.
7. Reinstall the flywheel nut: Reinstall the flywheel nut and tighten it to the specified torque.
8. Reinstall the starter assembly: Reinstall the starter assembly onto the engine.
9. Reinstall the spark plug: Reinstall the spark plug into the cylinder head.

Compression Test: The Heart of the Matter

If the fuel and ignition systems are working properly, the next thing to check is the engine’s compression. Compression is a measure of how well the engine seals the air-fuel mixture in the cylinder. Low compression can be caused by worn piston rings, a damaged cylinder, or leaky valves.

Technical Details:

• Compression Tester: A compression tester is a gauge that measures the pressure inside the cylinder when the engine is cranked.
• Compression Reading: The compression reading should be within the range specified in the service manual. For the MS 260, a healthy engine should have a compression reading of around 120-150 PSI.
• Low Compression: If the compression reading is below the specified range, the engine may have worn piston rings, a damaged cylinder, or leaky valves.

Actionable Steps:

1. Warm up the engine: Run the engine for a few minutes to warm it up.
2. Remove the spark plug: Remove the spark plug from the cylinder head.
3. Install the compression tester: Install the compression tester into the spark plug hole.
4. Crank the engine: Crank the engine over several times with the throttle wide open.
5. Record the reading: Record the highest compression reading on the gauge.
6. Interpret the results: Compare the compression reading to the specifications in the service manual. If the compression reading is low, perform a wet compression test.

Wet Compression Test:

A wet compression test can help determine if the low compression is caused by worn piston rings. To perform a wet compression test, add a small amount of oil (about a tablespoon) to the cylinder through the spark plug hole. Then, repeat the compression test. If the compression reading increases significantly after adding oil, the piston rings are likely worn. If the compression reading does not increase, the problem may be with the valves or the cylinder.

What Low Compression Means:

• Worn Piston Rings: This is the most common cause of low compression. Over time, the piston rings wear down and no longer seal the cylinder effectively.
• Damaged Cylinder: A scratched or scored cylinder wall can also cause low compression.
• Leaky Valves: If the valves are not sealing properly, air and fuel can leak out of the cylinder, resulting in low compression.
• Blown Head Gasket: Although less common on the MS 260 than on larger engines, a blown head gasket can also cause a loss of compression.

Addressing Low Compression:

Unfortunately, fixing low compression typically requires a major engine overhaul, which can be expensive and time-consuming. Depending on the severity of the problem, it may be more cost-effective to replace the entire engine or the chainsaw.

Air Intake Analysis: Breathing Easy

A clean air intake is essential for proper engine performance. A clogged air filter or obstructed air intake can restrict airflow, leading to a rich fuel mixture and hard starting.

1. Air Filter Inspection and Cleaning

The air filter prevents dirt and debris from entering the engine. A clogged air filter restricts airflow, which can cause the engine to run poorly.

Technical Details:

• Air Filter Type: The MS 260 typically uses a foam or felt air filter.
• Cleaning Interval: I recommend cleaning the air filter at least once a month, or more frequently if you’re working in dusty conditions.

Actionable Steps:

1. Remove the air filter cover: Remove the air filter cover from the engine.
2. Remove the air filter: Remove the air filter from the air filter housing.
3. Inspect the air filter: Examine the air filter for dirt, debris, or damage.
4. Clean the air filter:
   • Foam filter: Wash the foam filter in warm, soapy water. Rinse thoroughly and allow to air dry.
   • Felt filter: Tap the felt filter against a hard surface to remove loose dirt and debris. You can also use compressed air to blow out the filter.
5. Reinstall the air filter: Reinstall the air filter into the air filter housing.
6. Reinstall the air filter cover: Reinstall the air filter cover onto the engine.

2. Intake Manifold Inspection

The intake manifold connects the carburetor to the cylinder head. A cracked or damaged intake manifold can leak air, which can cause the engine to run lean.

Actionable Steps:

1. Inspect the intake manifold: Examine the intake manifold for cracks, leaks, or damage.
2. Check the intake manifold gasket: Make sure the intake manifold gasket is in good condition and properly seated.
3. Tighten the intake manifold bolts: Tighten the intake manifold bolts to the specified torque.

If the intake manifold is cracked or damaged, it must be replaced.

Exhaust System Evaluation: Letting Off Steam

A clear exhaust system is crucial for efficient engine operation. A clogged exhaust port or muffler can restrict exhaust flow, leading to reduced power and hard starting.

1. Exhaust Port Inspection and Cleaning

The exhaust port is the opening in the cylinder head that allows exhaust gases to escape. Over time, carbon deposits can build up in the exhaust port, restricting exhaust flow.

Technical Details:

• Carbon Buildup: Carbon buildup is a common problem in 2-stroke engines. It’s caused by the incomplete combustion of fuel and oil.

Actionable Steps:

1. Remove the muffler: Remove the muffler from the engine.
2. Inspect the exhaust port: Examine the exhaust port for carbon buildup.
3. Clean the exhaust port: Use a scraper or wire brush to remove the carbon deposits from the exhaust port. Be careful not to damage the cylinder head.
4. Reinstall the muffler: Reinstall the muffler onto the engine.

2. Muffler Inspection and Cleaning

The muffler is responsible for reducing the noise of the engine. A clogged muffler can restrict exhaust flow, which can cause the engine to run poorly.

Technical Details:

• Spark Arrestor Screen: Many mufflers have a spark arrestor screen, which prevents sparks from escaping the exhaust system. This screen can become clogged with carbon deposits over time.

Actionable Steps:

1. Inspect the muffler: Examine the muffler for carbon buildup or damage.
2. Clean the muffler:
   • Remove the spark arrestor screen: Remove the spark arrestor screen from the muffler.
   • Clean the spark arrestor screen: Use a wire brush to clean the carbon deposits from the spark arrestor screen.
   • Reinstall the spark arrestor screen: Reinstall the spark arrestor screen into the muffler.
3. Reinstall the muffler: Reinstall the muffler onto the engine.

Personal Experience: I once had an MS 260 that was running sluggishly. I checked everything – fuel, ignition, compression – and couldn’t find anything wrong. Finally, I decided to inspect the muffler and found that the spark arrestor screen was completely clogged with carbon. After cleaning the screen, the saw ran like new.

Troubleshooting Chart

To summarize, here’s a handy troubleshooting chart to guide you through the process:

Safety First: A Word of Caution

Working on a chainsaw can be dangerous. Always follow these safety precautions:

• Wear safety glasses: Protect your eyes from flying debris.
• Wear gloves: Protect your hands from cuts and abrasions.
• Disconnect the spark plug wire: Prevent accidental starting.
• Work in a well-ventilated area: Avoid breathing exhaust fumes.
• Consult the owner’s manual: Follow the manufacturer’s instructions.
• If you’re not comfortable, seek professional help: Don’t attempt repairs beyond your skill level.

Case Study: Reviving a Neglected MS 260

I once acquired a used MS 260 from a friend who had left it sitting in his garage for several years. The saw was in rough shape and wouldn’t start. Here’s what I did to get it running again:

1. Fuel System Overhaul: Drained the old fuel, replaced the fuel filter, and thoroughly cleaned the carburetor. The carburetor was heavily gummed up, requiring a complete disassembly and soaking in carburetor cleaner.
2. Ignition System Tune-Up: Replaced the spark plug and tested the ignition module. The spark plug was heavily fouled, and the ignition module was producing a weak spark. I replaced both components.
3. Compression Test: Performed a compression test and found that the compression was slightly low (around 110 PSI). I added a small amount of oil to the cylinder and repeated the test. The compression increased to 130 PSI, indicating worn piston rings.
4. Exhaust System Cleaning: Removed the muffler and cleaned the exhaust port and spark arrestor screen. The spark arrestor screen was completely clogged with carbon.
5. Reassembly and Adjustment: Reassembled the saw and adjusted the carburetor according to the factory settings.

After these repairs, the MS 260 started easily and ran smoothly. While the compression was still slightly low, the saw had plenty of power for most tasks. This case study highlights the importance of a thorough inspection and methodical troubleshooting when dealing with a hard-starting chainsaw.

Preventative Maintenance: Avoiding Future Headaches

The best way to avoid hard starting problems is to perform regular preventative maintenance. Here are some tips:

• Use fresh fuel: Always use fresh fuel and add a fuel stabilizer if you plan to store the saw for an extended period.
• Clean the air filter regularly: Clean the air filter at least once a month, or more frequently if you’re working in dusty conditions.
• Replace the spark plug annually: Replace the spark plug at least once a year.
• Inspect the fuel lines: Inspect the fuel lines for cracks or leaks.
• Clean the carburetor: Clean the carburetor periodically, especially if the saw is running poorly.
• Sharpen the chain: Keep the chain sharp to reduce engine load.
• Store the saw properly: Store the saw in a clean, dry place.

Data Points & Statistics:

• Fuel Degradation: Studies show that gasoline can lose up to 5% of its octane rating within 30 days of storage, leading to reduced engine performance.
• Air Filter Impact: A clogged air filter can reduce engine power by as much as 20%, while increasing fuel consumption by 10%.
• Spark Plug Performance: A worn spark plug can reduce fuel efficiency by up to 30% and increase emissions.
• Compression Loss: A 10% reduction in compression can result in a 15% loss of engine power.

The Importance of Proper Chain Maintenance

While not directly related to starting issues, a dull chain places extra strain on the engine, which can exacerbate existing problems. A sharp chain requires less power to cut through wood, reducing the load on the engine and improving fuel efficiency.

Technical Details:

• Chain Sharpening Angle: The correct sharpening angle for the MS 260 chain is typically 30 degrees.
• Depth Gauge Setting: The depth gauge setting should be 0.025 inches (0.635 mm).
• Filing Technique: Use a round file of the correct size (typically 5/32 inch) to sharpen the cutters. File each cutter evenly, maintaining the correct angle and depth.

Personal Tip: I use a chain filing guide to ensure consistent sharpening angles. It’s a worthwhile investment for maintaining a sharp chain.

Final Thoughts: Persistence Pays Off

Troubleshooting a hard-starting chainsaw can be frustrating, but with patience and a methodical approach, you can usually get it running again. Don’t be afraid to experiment and try different solutions. And if you get stuck, don’t hesitate to seek professional help. Remember, a well-maintained MS 260 is a valuable tool that can provide years of reliable service. So, keep your fuel fresh, your spark plug clean, and your chain sharp, and you’ll be ready to tackle any woodcutting task. Now, get out there and make some sawdust!

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