Common Stihl MS 251 problems include starting difficulties and carburetor issues. Users may also experience chain tensioner and oiler malfunctions.
Stihl chainsaws, like the MS 251, are known for their reliability and performance, yet they are not immune to challenges.
Owners often report troubles with starting the chainsaw – a problem typically related to a faulty spark plug or fuel system complications.
Carburetor problems, which can result in irregular engine performance, are not uncommon due to buildup or incorrect adjustments.
Additionally, the MS 251’s chain tensioner and oiling system can malfunction, leading to poor chain lubrication and increased wear.
Common Issues With Stihl MS 251
Stihl MS 251 chainsaws are known for their rugged build and reliability, but like any piece of machinery, they can encounter problems.
Understanding these issues can help users diagnose and resolve them swiftly, ensuring minimal downtime.
A frequent concern for Stihl MS 251 users is difficulty in starting the chainsaw.
This annoyance can be due to a variety of factors:
- Dirty air filters can restrict airflow.
- Spark plug issues might prevent ignition.
- Fuel problems, such as old or contaminated fuel, could hamper engine start.
Regular maintenance and part replacements can often resolve these start-up obstacles.
Low Power Output
Another issue that can arise is low power output. Several factors can cause the Stihl MS 251 to perform below its potential peak power:
- Clogged exhaust ports or a dirty muffler screen can affect engine breathing.
- An improperly adjusted or malfunctioning carburetor could impact the fuel mixture.
- Worn internal engine components may reduce compression and power.
Attending to these aspects can often restore the chainsaw to its full capacity.
Chain Oiling Problems
Proper chain lubrication is critical for the Stihl MS 251. Issues in this area might involve:
|Clogged oil ports
|Debris or sawdust buildup
|Defective oil pump
|Wear and tear or component failure
|Incorrect oil type
|Non-recommended oils or viscosity issues
Cleaning ports, checking the pump, and using the correct oil can help alleviate these oiling problems.
The carburetor is central to the Stihl MS 251’s performance.
Carburetor issues may manifest as erratic idling, engine bogging, or failure to run at full power:
- Dirt or debris in the carburetor can obstruct fuel and airflow.
- Improper settings can disrupt the air-fuel mix, leading to performance issues.
- An aged carburetor might require rebuilding or replacement.
Meticulous cleaning and adjustments are often the key to resolving these carburetor-related problems.
Troubleshooting Hard Starting
Difficulty starting your Stihl MS 251 chainsaw can turn a day’s work into a frustrating ordeal.
Several culprits may be responsible for this common issue, but with a systematic approach, you can quickly identify and resolve the problem.
Addressing the three key areas—the spark plug, air filter, and carburetor—will often restore your machine to robust health. Follow these troubleshooting steps to ensure a smooth start every time.
Checking Spark Plug
A defective spark plug can lead to start-up challenges. Inspecting your spark plug should be your first step:
- Disconnect the spark plug wire and remove the plug using a socket wrench.
- Check for deposits, wear, or damage. A black, sooty plug may indicate a rich fuel mixture, while a white, blistered plug can signal a lean mixture or overheating.
- Clean the plug with a wire brush or replace it if necessary. Proper gap settings are crucial for ignition efficiency.
Cleaning Air Filter
A clogged air filter restricts airflow, complicating the start-up process. Follow these steps to clean your filter:
- Remove the filter cover and take out the air filter.
- Gently clean the filter with a soft brush or air blower. If it’s very dirty, wash it in soapy water, rinse, and let it dry thoroughly.
- With a clean filter, air can flow freely, improving the chances of a successful start.
Improper carburetor settings can make starting your chainsaw difficult. Here’s how to fine-tune the carburetor:
|Locate the carburetor adjustment screws
|These are often marked as H (high speed), L (low speed), and T (idle).
|Start with the L screw
|Adjust it clockwise until the engine runs smoothly at low speed.
|Adjust the H screw
|Ensure the engine transitions smoothly to high speed without stalling or producing excess smoke.
|Set the T screw
|It controls the idle; the chain should stop moving when the engine idles.
Tweaking these settings can greatly improve your chainsaw’s startability and overall performance.
In case these steps do not resolve starting issues, it may be necessary to consult a professional for further diagnosis.
Resolving Low Power Output
Owners of the Stihl MS 251 chainsaw often prize their machines for their power and reliability.
Yet, like any piece of power equipment, they can encounter issues.
One such problem is low power output, which can turn a usually robust chainsaw into a less effective tool.
Thankfully, several troubleshooting techniques can address this problem, improving your chainsaw’s performance and getting you back to work efficiently.
Checking For Air Leaks
One of the common causes for low power output is an air leak in the chainsaw’s system.
Air leaks can occur in the intake manifold, crankcase, or around the carburetor gaskets.
Identify and fix any leaks to prevent air from bypassing the normal intake route. Here are steps to help check for air leaks:
- Closely inspect all gaskets and seals for signs of wear or damage.
- Use a specialized detection spray to help identify any areas where air might be escaping.
- If a leak is present, replace the affected gaskets or seals immediately.
Cleaning Exhaust Spark Arrestor
The spark arrestor is an important safety feature on your Stihl MS 251; however, it can become clogged with soot over time, leading to reduced engine power.
Maintaining a clean spark arrestor is essential for optimal performance. Here’s how to keep it clean:
- Remove the muffler cover to access the spark arrestor.
- Using a wire brush, gently scrub the spark arrestor to remove any debris or buildup.
- Before reassembling, make sure the arrestor is completely dry.
Inspecting Fuel Filter
A clogged fuel filter can starve your chainsaw’s engine of fuel, leading to low power and stalling.
For sustained power and efficiency, maintain a clean fuel filter with these tips:
- Locate and remove the fuel filter from the fuel tank, usually attached to the end of the fuel line.
- Rinse the filter in fresh gasoline to dislodge any trapped particles.
- If the filter appears excessively dirty or damaged, replacement is necessary.
- Before reinserting, inspect the fuel lines for any signs of cracking or wear.
Fixing Chain Oiling Problems
When your reliable Stihl MS 251 chainsaw encounters chain oiling issues, it can hinder the saw’s performance and longevity.
A well-oiled chain is crucial for efficient cutting and to minimize wear.
Understanding how to troubleshoot the chain oiling system will save you time and maintain your saw in top condition.
Adjusting Oil Flow Rate
A common issue with the Stihl MS 251 is insufficient oil reaching the chain. This can be rectified by adjusting the oil flow rate.
Adjust the oil flow according to the bar length and the type of wood you’re cutting. To do this:
- Locate the oil flow adjustment screw on the underside of the saw.
- Use a screwdriver to turn the screw—clockwise to decrease or counterclockwise to increase oil flow.
- After adjustment, run the saw and check the chain for adequate oiling.
Cleaning Oil Ports
Over time, the oil ports on your chainsaw can become clogged with debris, which impedes oil flow.
Regular cleaning ensures consistent performance. Clean the oil ports by following these steps:
- Turn off the chainsaw and ensure it’s cool before starting.
- Remove the chain and guide bar to access the oil ports.
- Use a fine brush or compressed air to clean out the ports.
- Wipe clean with a cloth and reassemble your saw.
Checking Oil Pump
The oil pump is integral to the chainsaw’s oiling system. A faulty oil pump can result in poor chain lubrication. Inspect the oil pump by:
- Disassembling the saw to access the pump.
- Examining the pump for damage or wear.
- Checking for any obstructions in the pump.
- Replacing the pump if necessary, or cleaning it for reuse.
Regular maintenance, including the steps above, will prevent most oiling issues and keep your Stihl MS 251 running smoothly.
Embrace proactive care for uninterrupted, efficient cutting.
The carburetor is an integral part of the Stihl MS 251 chainsaw, mixing air and fuel to power the engine.
However, over time, this crucial component can experience several issues that hinder your chainsaw’s performance.
Proper troubleshooting and maintenance of the carburetor can ensure your MS 251 runs smoothly and efficiently.
Adjusting Idle Speed
The idle speed of your Stihl MS 251 can impact its start-up and performance.
An improperly adjusted idle can lead to the chainsaw stalling or running erratically. To adjust the idle speed:
- Locate the idle speed screw, which is usually marked with a “T” or “LA”.
- Start the chainsaw and let it warm up.
- Turn the screw clockwise for a higher idle speed or counterclockwise for a lower speed.
- Adjust until the saw runs smoothly without the chain moving when idling.
A dirty carburetor can cause your chainsaw to run poorly or not start at all.
Regular cleaning is vital for peak performance. Here’s how to clean your carburetor:
- Turn off the chainsaw and ensure it is completely cool.
- Remove the carburetor cover and air filter.
- Detach the carburetor from the engine.
- Spray carburetor cleaner directly into the carburetor, and onto the throttle and choke plates.
- Clean all visible debris using a soft brush or compressed air.
- Reassemble the components once everything is dry.
Replacing Carburetor If Necessary
Sometimes cleaning won’t solve the problem, and the carburetor will need replacement.
Signs that a replacement is due can include substantial damage or persistent performance issues even after cleaning and adjustment.
Typically, a carburetor will last a long time with proper maintenance, so be sure to exhaust other remedies before proceeding with this more drastic step.
- Purchase an authentic Stihl replacement carburetor compatible with the MS 251 model.
- Disconnect the fuel line and remove the old carburetor.
- Install the new carburetor, reconnecting all lines and linkages.
- Make fine adjustments as per the chainsaw’s operating manual.
- Test the chainsaw to ensure it starts and idles correctly.
Frequently Asked Questions On Stihl MS 251 Problems
What Are Common Issues With Stihl MS 251?
The Stihl MS 251 chainsaw often encounters problems such as starting difficulties, chain tension issues, carburetor malfunctions, and oiler failures.
How To Troubleshoot Stihl MS 251 Starting Problems?
Check the spark plug, clean the air filter, and ensure the correct fuel mix to solve starting issues with the Stihl MS 251.
Can A Dirty Air Filter Affect MS 251 Performance?
Yes, a clogged air filter restricts airflow, causing poor engine performance and potential starting problems in the MS 251.
Stihl MS 251 Chainsaw Leaks Oil: What’s Wrong?
Leaking oil in the MS 251 may indicate a problem with the oiler system or a loose oil cap.
Why Does The Stihl MS 251’s Chain Tension Misbehave?
Improper chain tension on the MS 251 is often due to wear, incorrect adjustment, or a worn-out guide bar.
Confronting issues with your Stihl MS 251 chainsaw can be frustrating. Despite this, it’s a reliable tool favored by many professionals.
For optimal performance, regular maintenance is key. Troubleshoot effectively by referencing our suggestions.
Keep your saw running smoothly and tackle any task with confidence. Stay safe and ensure your equipment is in top condition.