Stihl MS250 Starting Issues (5 Quick Fixes for Loggers)

Ever bitten into a perfectly ripe apple, only to find it’s mushy and tasteless inside? The disappointment is real, right? Well, that’s how I feel when my Stihl MS250, usually a reliable workhorse, refuses to start. It’s a letdown, especially when I’m counting on it to get through a pile of firewood after a long day in the woods.

Over the years, I’ve faced my fair share of starting issues with my MS250. From flooded engines to fouled spark plugs, I’ve troubleshooted it all. Through trial and error, and a healthy dose of research, I’ve developed a few quick fixes that have gotten me back up and running more often than not.

In this guide, I’ll share my experience and insights into diagnosing and fixing common Stihl MS250 starting problems. I will walk you through five quick fixes I’ve found most effective in the field.

Stihl MS250 Starting Issues: 5 Quick Fixes for Loggers

Let’s dive into the specific issues that might be plaguing your MS250 and how to tackle them head-on.

1. The Flooded Engine Fiasco

One of the most common reasons a Stihl MS250 refuses to start is a flooded engine. This happens when too much fuel enters the cylinder, making it difficult for the spark plug to ignite the air-fuel mixture.

My Experience: I remember one particularly cold morning, I was eager to get started on a large oak log. I pulled the starter cord repeatedly, without hesitation, convinced it would eventually catch. Instead, I flooded the engine. The frustration was palpable as I wasted precious time trying to get it going.

The Fix:

• Step 1: Identify the Flood: You’ll usually smell a strong odor of gasoline and the engine will sound “wet” when you pull the starter cord.
• Step 2: Engage the Choke (If Not Already): Push the choke lever all the way down (cold start position).
• Step 3: Full Throttle: Hold the throttle lever wide open. This allows maximum air to enter the cylinder, helping to clear out the excess fuel.
• Step 4: Pull the Starter Cord: Pull the starter cord firmly and repeatedly (5-10 times). The goal is to crank the engine and expel the excess fuel.
• Step 5: Normal Starting Procedure: Return the choke to the half-choke position (if applicable) or the run position, release the throttle, and try starting the saw normally.
• Step 6: Patience is Key: If it still doesn’t start, wait a few minutes and repeat the process. Sometimes, it takes a little persistence.

Why This Works: Opening the throttle and pulling the starter cord with the choke engaged allows more air into the cylinder, diluting the fuel mixture and helping to evaporate the excess gasoline.

Pro Tip: Avoid excessive priming. Over-priming is a common cause of flooding. Only prime the saw a few times, as recommended in the owner’s manual.

Takeaway: A flooded engine can be a real headache, but understanding the proper procedure to clear it can save you a lot of time and frustration.

2. Spark Plug Problems: The Ignition Culprit

The spark plug is a critical component of your MS250’s ignition system. A fouled, dirty, or damaged spark plug can prevent the engine from starting.

My Experience: I once spent an entire afternoon troubleshooting a saw that wouldn’t start, only to discover the spark plug was the culprit. It looked fine at first glance, but upon closer inspection, the electrode was cracked. A simple spark plug replacement solved the problem immediately.

The Fix:

• Step 1: Locate the Spark Plug: On the Stihl MS250, the spark plug is typically located under a small cover on the side of the engine.
• Step 2: Remove the Spark Plug: Use the spark plug wrench (usually included in the saw’s toolkit) to carefully remove the spark plug.
• Step 3: Inspect the Spark Plug:
  • Check for Fouling: Look for carbon deposits, oil, or fuel on the electrode.
  • Check for Damage: Inspect the electrode for cracks, chips, or excessive wear.
  • Check the Gap: Use a spark plug gap tool to ensure the gap between the electrode and the ground electrode is within the manufacturer’s specification (typically 0.5 mm or 0.020 inches for the MS250).
• Step 4: Clean or Replace the Spark Plug:
  • Cleaning: If the spark plug is only slightly fouled, you can try cleaning it with a wire brush or spark plug cleaner.
  • Replacing: If the spark plug is heavily fouled, damaged, or the gap is incorrect, it’s best to replace it with a new one. Use the correct spark plug type recommended for the Stihl MS250 (e.g., NGK BPMR7A or Champion RCJ6Y).
• Step 5: Reinstall the Spark Plug: Carefully reinstall the spark plug, tightening it to the manufacturer’s specified torque (typically 15-20 Nm or 11-15 ft-lbs).

Why This Works: A clean, properly gapped spark plug ensures a strong, consistent spark, which is essential for igniting the air-fuel mixture.

Pro Tip: Keep a spare spark plug in your toolkit. It’s a small investment that can save you a lot of downtime in the field.

Takeaway: A faulty spark plug is a common cause of starting problems. Regular inspection and maintenance, or replacement when needed, can keep your MS250 running smoothly.

3. Fuel Issues: The Lifeblood of Your Chainsaw

The quality and delivery of fuel are critical for your MS250’s performance. Old fuel, a clogged fuel filter, or a blocked fuel line can all prevent the engine from starting.

My Experience: I once had a saw that would start and run for a few minutes, then die. I initially suspected the ignition system, but after checking the fuel filter, I found it completely clogged with debris. Replacing the filter solved the problem instantly.

The Fix:

• Step 1: Check the Fuel:
  • Fuel Age: Old fuel can degrade and become less volatile, making it difficult to start the engine. Use fresh fuel (less than 30 days old) mixed with the correct ratio of two-stroke oil (typically 50:1 for the MS250).
  • Fuel Contamination: Check for water or debris in the fuel tank. Drain the tank and refill with fresh fuel if necessary.
• Step 2: Inspect the Fuel Filter:
  • Location: The fuel filter is located inside the fuel tank, attached to the end of the fuel line.
  • Removal: Use a small hook or bent wire to carefully pull the fuel filter out of the tank.
  • Inspection: Check the filter for clogs, debris, or damage.
  • Cleaning or Replacement: Clean the filter with compressed air or replace it with a new one if necessary.
• Step 3: Check the Fuel Line:
  • Inspection: Inspect the fuel line for cracks, kinks, or leaks.
  • Replacement: Replace the fuel line if it’s damaged.
• Step 4: Check the Carburetor:
  • Clogged Carburetor: A clogged carburetor can restrict fuel flow to the engine.
  • Cleaning: If you suspect a clogged carburetor, you can try cleaning it with carburetor cleaner. Disassemble the carburetor carefully, following the manufacturer’s instructions, and spray all the jets and passages with cleaner.
  • Professional Service: If cleaning doesn’t solve the problem, it’s best to take the saw to a qualified technician for carburetor repair or replacement.

Why This Works: Clean, fresh fuel and a clear fuel delivery system ensure the engine receives the proper amount of fuel for combustion.

Pro Tip: Use a fuel stabilizer when storing your saw for extended periods. This will help prevent fuel degradation and keep the fuel system clean.

Takeaway: Fuel-related issues are a common cause of starting problems. Regular fuel system maintenance, including using fresh fuel, cleaning or replacing the fuel filter, and inspecting the fuel line, can prevent these issues.

4. Air Intake Obstructions: Suffocating Your Engine

Just like humans, a chainsaw needs air to breathe. A blocked air filter or obstructed air intake can prevent the engine from starting.

My Experience: I once worked in a particularly dusty environment, cutting firewood near a logging site. My saw started losing power and eventually wouldn’t start at all. The air filter was completely clogged with sawdust. Cleaning the filter restored the saw’s performance immediately.

The Fix:

• Step 1: Locate the Air Filter: The air filter is typically located under a cover on the top or side of the engine.
• Step 2: Remove the Air Filter: Remove the air filter cover and carefully remove the air filter.
• Step 3: Inspect the Air Filter: Check the filter for dirt, dust, sawdust, or other debris.
• Step 4: Clean the Air Filter:
  • Compressed Air: Use compressed air to blow the dirt and debris out of the filter. Blow from the inside out to avoid forcing the debris further into the filter.
  • Washing: If the filter is heavily soiled, you can wash it with warm, soapy water. Rinse thoroughly and allow it to dry completely before reinstalling.
  • Replacement: If the filter is damaged or excessively dirty, replace it with a new one.
• Step 5: Inspect the Air Intake: Check the air intake for any obstructions, such as leaves, twigs, or debris. Remove any obstructions.
• Step 6: Reinstall the Air Filter: Carefully reinstall the air filter and the air filter cover.

Why This Works: A clean air filter allows the engine to draw in the proper amount of air for combustion.

Pro Tip: Clean the air filter regularly, especially when working in dusty or dirty environments.

Takeaway: Air intake obstructions can prevent the engine from starting or cause it to run poorly. Regular air filter maintenance is essential for optimal performance.

5. Recoil Starter Problems: The Pulling Predicament

The recoil starter is the mechanism you use to manually start the engine. A broken recoil spring, damaged starter cord, or a seized starter clutch can prevent you from pulling the starter cord or engaging the engine.

My Experience: I was once deep in the woods when my starter cord snapped. I was miles from my truck and had to figure out a way to fix it in the field. I managed to tie the broken ends together, but it was a temporary fix. I learned my lesson and now always carry a spare starter cord.

The Fix:

• Step 1: Inspect the Starter Cord:
  • Check for Breaks: Look for any breaks, frays, or damage to the starter cord.
  • Replacement: If the cord is broken or damaged, replace it with a new one.
• Step 2: Inspect the Recoil Spring:
  • Check for Tension: If the starter cord pulls out easily without resistance, the recoil spring may be broken or have lost tension.
  • Replacement: Replacing the recoil spring can be tricky. It’s best to consult the saw’s repair manual or take it to a qualified technician.
• Step 3: Check the Starter Clutch:
  • Lubrication: The starter clutch may be seized or sticking. Try lubricating it with a small amount of light oil or grease.
  • Cleaning: Clean the starter clutch with a brush and solvent to remove any dirt or debris.
• Step 4: Check the Pawls:
  • Inspection: Examine the pawls (small levers that engage the flywheel) for wear or damage.
  • Lubrication: Ensure they move freely and are not sticking. Lubricate with a light oil if necessary.
• Step 5: Proper Pulling Technique:
  • Smooth Pull: Avoid jerking the starter cord. Pull it smoothly and steadily.
  • Full Extension: Pull the cord out to its full extension to engage the engine properly.
  • Retract Slowly: Allow the cord to retract slowly to prevent damage to the recoil mechanism.

Why This Works: A properly functioning recoil starter is essential for manually starting the engine.

Pro Tip: Use a gentle, smooth pull when starting the saw. Avoid yanking the cord, as this can damage the recoil mechanism.

Takeaway: Recoil starter problems can be frustrating, but understanding the components and how they work can help you troubleshoot and fix common issues.

Additional Tips for Stihl MS250 Maintenance

Beyond these quick fixes, regular maintenance is crucial for keeping your Stihl MS250 in top condition. Here are a few additional tips:

• Chain Sharpening: Keep your chain sharp for efficient cutting and reduced strain on the engine. I use a file and guide to maintain the correct cutting angle.
• Chain Lubrication: Ensure the chain is properly lubricated to prevent excessive wear and tear. I check the oil level regularly and use a high-quality bar and chain oil.
• Regular Cleaning: Clean the saw regularly to remove sawdust, debris, and oil buildup. Pay particular attention to the cooling fins and air intake.
• Proper Storage: Store the saw in a dry, well-ventilated area. Drain the fuel tank before storing the saw for extended periods.
• Follow the Owner’s Manual: Consult the owner’s manual for specific maintenance recommendations and schedules.

Understanding Two-Stroke Engines

The Stihl MS250 uses a two-stroke engine, which is different from the four-stroke engines found in cars and trucks. Understanding how a two-stroke engine works can help you diagnose and troubleshoot starting problems.

• Two-Stroke Cycle: In a two-stroke engine, the entire combustion cycle is completed in two strokes of the piston (one up and one down), compared to four strokes in a four-stroke engine.
• Fuel Mixture: Two-stroke engines require a mixture of gasoline and two-stroke oil. The oil lubricates the engine components, as there is no separate oil sump like in a four-stroke engine.
• Exhaust Ports: Two-stroke engines have exhaust ports in the cylinder walls that are uncovered by the piston as it moves down, allowing exhaust gases to escape.
• Simpler Design: Two-stroke engines are generally simpler in design than four-stroke engines, making them lighter and more powerful for their size.

Safety First: Chainsaw Safety Practices

Operating a chainsaw can be dangerous if proper safety precautions are not followed. Here are some essential safety practices:

• Personal Protective Equipment (PPE): Always wear appropriate PPE, including a helmet, eye protection, hearing protection, gloves, and chainsaw chaps.
• Safe Cutting Techniques: Use proper cutting techniques to avoid kickback and other hazards.
• Clear Work Area: Clear the work area of obstacles and ensure you have a stable footing.
• Inspect the Saw: Before each use, inspect the saw for any damage or loose parts.
• Emergency Plan: Have an emergency plan in place in case of an accident.

Case Studies: Real-World Examples

Here are a couple of case studies based on my own experiences:

• Case Study 1: The Stubborn Start: I was cutting firewood for a local charity when my MS250 refused to start. I checked the fuel, spark plug, and air filter, but everything seemed fine. After further investigation, I discovered a small crack in the fuel line. Replacing the fuel line solved the problem.
• Case Study 2: The Overheated Engine: I was working on a large logging project during a hot summer day. My MS250 started losing power and eventually stalled. I let the engine cool down, cleaned the air filter, and refueled the saw. It started up and ran fine after that. The problem was likely overheating due to the hot weather and a dirty air filter.

Environmental Considerations

As loggers and wood processors, we have a responsibility to protect the environment. Here are a few environmental considerations:

• Sustainable Logging Practices: Use sustainable logging practices to minimize the impact on the forest.
• Proper Waste Disposal: Dispose of used oil, fuel, and other waste materials properly.
• Noise Pollution: Minimize noise pollution by using mufflers and avoiding unnecessary idling.
• Erosion Control: Implement erosion control measures to prevent soil erosion and water pollution.

The Future of Chainsaws

Chainsaw technology is constantly evolving. Here are a few trends to watch:

• Battery-Powered Chainsaws: Battery-powered chainsaws are becoming more powerful and efficient, offering a quieter and more environmentally friendly alternative to gas-powered saws.
• Automatic Chain Sharpening: Some chainsaws now feature automatic chain sharpening systems, making it easier to maintain a sharp chain.
• Smart Chainsaws: Smart chainsaws are equipped with sensors and electronics that monitor performance and provide data to the user.

Conclusion: Keeping Your MS250 Running Strong

The Stihl MS250 is a reliable and versatile chainsaw that can handle a wide range of tasks. By understanding the common causes of starting problems and following these quick fixes, you can keep your MS250 running strong for years to come. Remember to perform regular maintenance, use proper safety practices, and be mindful of the environment. With a little care and attention, your MS250 will be a valuable tool for all your logging and wood processing needs.

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