Stihl Chainsaw MS260C Troubleshooting (5 Expert Fixes)

The Stihl MS260C is a workhorse. I’ve spent countless hours in the woods with mine, felling trees and bucking firewood. When it’s running right, it’s a dream. But like any piece of machinery, it can have its hiccups. Over the years, I’ve learned to troubleshoot the common problems that plague this model. This guide shares my personal experiences and expertise to help you get your MS260C back in action.

Stihl Chainsaw MS260C Troubleshooting: 5 Expert Fixes

The Stihl MS260C is a popular choice for both homeowners and professionals due to its power, reliability, and relatively light weight. However, like any chainsaw, it can encounter problems that require troubleshooting. This guide will walk you through five common issues I’ve encountered with my MS260C and the expert fixes I’ve used to resolve them.

1. Chainsaw Won’t Start

A chainsaw that refuses to start is frustrating, but usually the cause is simple. I’ve been there, pulling the cord until my arm feels like it’s going to fall off. Here’s how I approach this problem systematically:

Fuel Issues

Old Fuel: I’ve made this mistake more than once. Stale fuel is the most common culprit. Gasoline breaks down over time, especially when mixed with 2-cycle oil. This can lead to a gummy residue that clogs the carburetor. I always recommend using fresh fuel (less than 30 days old) and a high-quality 2-cycle oil mixed at the correct ratio (usually 50:1 for the MS260C, but always check your owner’s manual). I now label my fuel cans with the date to avoid this issue.
- Action: Drain the old fuel and replace it with a fresh mixture. I use a fuel stabilizer in my gas can now to extend the life of the fuel.
Fuel Filter: A clogged fuel filter restricts fuel flow to the carburetor. This is an easy fix.
- Action: Locate the fuel filter inside the fuel tank (attached to the fuel line). Use a small hook or bent wire to pull it out. Inspect the filter for debris. If it’s dirty, replace it with a new one. I keep a few spares on hand.
Fuel Line: Inspect the fuel line for cracks, kinks, or leaks. A damaged fuel line can prevent fuel from reaching the engine.
- Action: Replace any damaged fuel lines.

Spark Issues

Spark Plug: A faulty spark plug can prevent the engine from firing. I’ve seen plugs get fouled by carbon buildup or simply fail over time.
- Action: Remove the spark plug and inspect it. It should be clean and dry. If it’s wet, the engine may be flooded. If it’s black and sooty, it’s likely fouled. Clean the plug with a wire brush or replace it. Check the spark by grounding the plug against the engine block and pulling the starter cord. You should see a strong, blue spark. If not, the spark plug is likely bad. I always carry a spare spark plug in my saw case. The correct spark plug for the MS260C is typically an NGK BPMR7A or equivalent. Gap the new spark plug to 0.020 inches (0.5 mm) before installing it.
Ignition Coil: The ignition coil provides the high voltage needed to create a spark. If the coil is faulty, the engine won’t start.
- Action: This requires a multimeter to test the coil’s resistance. Consult your owner’s manual or a repair manual for the specific resistance values for your MS260C. If the coil doesn’t meet the specifications, it needs to be replaced. This is a more involved repair, and I sometimes take it to a professional.

Compression Issues

Low Compression: Low compression makes it difficult for the engine to start.
- Action: A compression test requires a compression tester. Screw the tester into the spark plug hole and pull the starter cord several times. The reading should be within the manufacturer’s specifications (typically around 120-150 PSI for the MS260C). If the compression is low, the engine may need more serious repairs, such as piston ring replacement. I usually leave this to a professional.

2. Chainsaw Starts but Stalls Immediately

This is another common problem I’ve faced. The engine fires up, sounds promising for a moment, and then dies. This usually points to fuel or carburetor issues.

Carburetor Problems

Dirty Carburetor: The carburetor mixes air and fuel to create a combustible mixture. A dirty or clogged carburetor is a frequent cause of stalling. Ethanol in gasoline can leave deposits that clog the small passages in the carburetor.
- Action: The best solution is to clean the carburetor. You can use a carburetor cleaner spray. If that doesn’t work, you may need to disassemble the carburetor and clean each component individually. I use a carburetor cleaning kit with small brushes and wires to clean the jets and passages. Pay close attention to the high and low-speed jets. I also recommend replacing the carburetor gaskets and diaphragms during cleaning, as they can become brittle and cracked over time.
Carburetor Adjustment: The carburetor has adjustment screws (usually labeled “H” for high speed and “L” for low speed) that control the air/fuel mixture. Incorrect adjustments can cause stalling.
- Action: Refer to your owner’s manual for the recommended carburetor settings. As a starting point, turn both screws clockwise until they are lightly seated, then back them out the recommended number of turns (usually around 1 to 1.5 turns). Start the engine and adjust the screws until the engine idles smoothly and accelerates without hesitation. I usually adjust the low-speed screw first, then the high-speed screw. Be careful not to overtighten the screws, as this can damage the carburetor.
Idle Speed: The idle speed screw controls the engine’s idle speed. If the idle speed is too low, the engine may stall.
- Action: Turn the idle speed screw clockwise to increase the idle speed until the engine idles smoothly without stalling.

Fuel Delivery Issues

Ventilation: The fuel tank needs to be properly vented to allow fuel to flow to the carburetor. A clogged vent can create a vacuum in the tank, preventing fuel flow.
- Action: Locate the fuel tank vent (usually a small hole in the fuel cap or near the fuel tank). Make sure it’s clear of debris. I use a small wire to clean it out.
Impulse Line: The impulse line connects the engine crankcase to the fuel pump in the carburetor. This line provides the pressure pulse that operates the fuel pump. A cracked or leaking impulse line can prevent the fuel pump from working properly.
- Action: Inspect the impulse line for cracks or leaks. Replace it if necessary.

Takeaway: Carburetor issues are often the root cause of stalling problems. Cleaning and adjusting the carburetor can often resolve the issue. Don’t forget to check the fuel tank vent and impulse line.

3. Chainsaw Runs Poorly (Low Power, Hesitation)

When my MS260C lacks power or hesitates when I try to cut, it’s usually a sign of an air/fuel mixture problem or a clogged exhaust.

Air/Fuel Mixture Problems

Dirty Air Filter: A dirty air filter restricts airflow to the engine, causing a rich air/fuel mixture (too much fuel, not enough air).
- Action: Clean or replace the air filter. I clean mine regularly, especially when working in dusty conditions.
Carburetor Adjustment: An improperly adjusted carburetor can cause a lean or rich air/fuel mixture. A lean mixture (too much air, not enough fuel) can cause hesitation and low power. A rich mixture can cause the engine to run sluggishly and produce excessive smoke.
- Action: Readjust the carburetor settings according to your owner’s manual.
Incorrect Fuel Mixture: Using the wrong fuel mixture (too much or too little oil) can cause engine problems.
- Action: Always use the correct fuel mixture (usually 50:1 for the MS260C).

Exhaust Problems

Spark Arrestor Screen: The spark arrestor screen prevents sparks from exiting the exhaust, reducing the risk of fire. A clogged spark arrestor screen can restrict exhaust flow, causing low power and hesitation. I’ve had this happen when cutting dry, resinous wood.
- Action: Remove the spark arrestor screen from the muffler and clean it with a wire brush. You can also use carburetor cleaner to dissolve carbon deposits.
Muffler: A clogged muffler can also restrict exhaust flow.
- Action: Inspect the muffler for carbon buildup. If it’s heavily clogged, you may need to remove it and clean it thoroughly.

Other Potential Causes

Worn Piston Rings: Worn piston rings can cause low compression, leading to low power.
- Action: A compression test can help determine if the piston rings are worn. If the compression is low, the engine may need more serious repairs.
Cylinder Damage: Scratches or scoring on the cylinder walls can also cause low compression.
- Action: Inspect the cylinder walls for damage. This requires removing the cylinder head.

Takeaway: Pay attention to the air/fuel mixture and exhaust flow. Cleaning the air filter and spark arrestor screen are easy maintenance tasks that can significantly improve performance.

4. Chainsaw Chain Problems

A dull or improperly tensioned chain can make cutting difficult and even dangerous. I’ve learned the hard way that maintaining a sharp chain is crucial for safety and efficiency.

Chain Sharpness

Dull Chain: A dull chain requires more force to cut and can cause the saw to kick back.
- Action: Sharpen the chain regularly. I use a chainsaw file and a filing guide to maintain the correct cutting angle and depth. You can also use a chainsaw sharpener. I prefer hand filing because I have more control.
Damaged Chain: A chain with damaged teeth or a broken tie strap needs to be repaired or replaced.
- Action: Inspect the chain for damage. Replace any damaged parts or replace the entire chain.

Chain Tension

Loose Chain: A loose chain can derail from the bar and cause injury.
- Action: Adjust the chain tension so that it fits snugly against the bar but can still be pulled around by hand. I usually tighten the chain until I can pull it about 1/8 inch away from the bar in the middle.
Tight Chain: A tight chain can bind and overheat, damaging the bar and chain.
- Action: Loosen the chain tension until it moves freely around the bar.

Chain Lubrication

Insufficient Lubrication: Insufficient chain lubrication can cause the chain and bar to overheat and wear out prematurely.
- Action: Make sure the chain oil reservoir is full and that the oiler is functioning correctly. I use a high-quality bar and chain oil.
Oiler Problems: A clogged or malfunctioning oiler can prevent the chain from being properly lubricated.
- Action: Check the oiler for clogs. You can use a small wire to clean out the oiler hole on the bar. If the oiler is not working, it may need to be repaired or replaced.

Bar Problems

Worn Bar: A worn bar can cause the chain to derail and make cutting difficult.
- Action: Inspect the bar for wear. If the bar is worn, it may need to be replaced.
Damaged Bar: A damaged bar can also cause chain problems.
- Action: Repair or replace any damaged bars. I regularly flip the bar to ensure even wear.

Takeaway: Chain maintenance is essential for safe and efficient chainsaw operation. Keep the chain sharp, properly tensioned, and well-lubricated. Regularly inspect the bar for wear and damage.

5. Chainsaw Overheating

Overheating can damage the engine and shorten the life of your chainsaw. It’s crucial to identify and address the causes of overheating.

Airflow Obstruction

Dirty Cooling Fins: The cooling fins on the cylinder head dissipate heat. Dirty or clogged cooling fins restrict airflow and cause the engine to overheat.
- Action: Clean the cooling fins regularly with a brush or compressed air. I do this after every few uses, especially in the summer months.
Restricted Air Intake: A dirty air filter or clogged air intake can restrict airflow to the engine, causing it to overheat.
- Action: Clean or replace the air filter. Make sure the air intake is clear of debris.

Fuel Mixture Problems

Lean Air/Fuel Mixture: A lean air/fuel mixture (too much air, not enough fuel) can cause the engine to overheat.
- Action: Readjust the carburetor settings to richen the air/fuel mixture.
Incorrect Fuel Mixture: Using the wrong fuel mixture (too much oil) can also cause overheating.
- Action: Always use the correct fuel mixture (usually 50:1 for the MS260C).

Other Potential Causes

Overloading the Engine: Forcing the chainsaw to cut through wood that is too thick or dense can cause the engine to overheat.
- Action: Use the correct cutting technique and avoid overloading the engine. Let the saw do the work.
Worn Piston Rings: Worn piston rings can cause excessive friction and heat, leading to overheating.
- Action: A compression test can help determine if the piston rings are worn.
Cylinder Damage: Scratches or scoring on the cylinder walls can also cause excessive friction and heat.
- Action: Inspect the cylinder walls for damage.

Preventative Measures

Proper Maintenance: Regular maintenance, including cleaning the air filter, cooling fins, and spark arrestor screen, can help prevent overheating.
Sharp Chain: A sharp chain reduces the amount of force required to cut, reducing the risk of overheating.
Correct Fuel Mixture: Always use the correct fuel mixture.
Avoid Overloading: Avoid overloading the engine by using the correct cutting technique and not forcing the saw.

Takeaway: Overheating is a serious problem that can damage your chainsaw. Keep the engine clean and properly tuned, and avoid overloading it.

Additional Tips and Considerations

Safety First: Always wear appropriate safety gear, including eye protection, hearing protection, gloves, and chainsaw chaps.
Read the Manual: Familiarize yourself with your owner’s manual. It contains valuable information about your chainsaw’s operation and maintenance.
Regular Maintenance: Perform regular maintenance, including cleaning the air filter, spark plug, and spark arrestor screen.
Use Quality Fuel and Oil: Use fresh, high-quality fuel and 2-cycle oil.
Store Properly: Store your chainsaw in a dry, safe place. Drain the fuel tank before storing the saw for extended periods.
Professional Help: Don’t hesitate to seek professional help if you’re not comfortable performing repairs yourself.
Record Keeping: Keep a log of maintenance and repairs. This will help you track the performance of your chainsaw and identify potential problems early on.
Chain Brake: Always ensure the chain brake is functioning correctly. This is a crucial safety feature.
Starting Procedure: Follow the correct starting procedure as outlined in your owner’s manual.

Conclusion

Troubleshooting a Stihl MS260C chainsaw can seem daunting, but by systematically addressing common issues like starting problems, stalling, low power, chain problems, and overheating, you can often get your saw back in top condition. Remember to prioritize safety, perform regular maintenance, and consult your owner’s manual for specific instructions. With a little patience and know-how, you can keep your MS260C running smoothly for years to come. I’ve found that taking the time to understand my saw has saved me countless hours and dollars in the long run. Happy cutting!

Stihl Chainsaw MS260C Troubleshooting (5 Expert Fixes)