Stihl MS170 How to Start (5 Essential Carburetor Fixes)

Warning: Working with chainsaws, especially troubleshooting carburetor issues, can be dangerous. Always disconnect the spark plug wire before working on the engine. Wear appropriate safety gear, including gloves, eye protection, and hearing protection. Improper carburetor adjustments can lead to engine damage or personal injury. If you are not comfortable performing these repairs, consult a qualified mechanic.

Understanding the User Intent: Why Are You Here?

Before we dive into the fixes, let’s understand why you’re likely reading this article. Based on the search term “Stihl MS170 How to Start (5 Essential Carburetor Fixes),” you’re probably experiencing one or more of these issues:

That experience taught me the value of understanding your equipment, diagnosing problems accurately, and budgeting effectively for repairs. This article is designed to help you do just that.

1. Carburetor Cleaning: The First Line of Defense

The Problem: Clogged Jets and Passages

Over time, the small jets and passages within the carburetor can become clogged with varnish, fuel residue, and debris. This restricts fuel flow, leading to starting problems, stalling, and poor performance.

The Solution: A Thorough Cleaning

Steps:

1. Remove the Air Filter: Unscrew the air filter cover and remove the filter. Clean or replace the filter if necessary. A dirty air filter can also contribute to starting problems.
2. Remove the Carburetor: Carefully disconnect the fuel lines and throttle linkage from the carburetor. Note their positions for reassembly. Unscrew the carburetor mounting bolts and remove the carburetor.
3. Disassemble the Carburetor: This is where things get a little tricky. Most MS170 carburetors are Walbro or Zama carburetors. Disassemble the carburetor carefully, noting the location of each part. Pay special attention to the jets, needles, and diaphragms. A carburetor repair kit (more on that later) often comes with a diagram.
4. Clean the Parts: Use carburetor cleaner spray to thoroughly clean all the parts. Pay special attention to the jets and passages. You can use a small wire or carburetor cleaning tool to clear any stubborn blockages. I often use guitar strings for this purpose, as they are thin and flexible.
5. Reassemble the Carburetor: Reassemble the carburetor carefully, following the diagram or your notes. Ensure all parts are properly seated.
6. Reinstall the Carburetor: Reinstall the carburetor on the saw, reconnecting the fuel lines and throttle linkage.
7. Adjust the Carburetor: After cleaning, you may need to adjust the carburetor settings. The MS170 typically has two adjustment screws: the “H” (high-speed) and “L” (low-speed) screws. Start with the factory settings (usually 1 turn out from fully closed for both screws) and fine-tune as needed.

Cost Considerations:

• Carburetor Cleaner: A can of carburetor cleaner typically costs between $5 and $15. I prefer CRC Carb & Choke Cleaner, which is readily available and effective.
• Carburetor Repair Kit: If the diaphragms or gaskets are damaged, you’ll need a carburetor repair kit. These kits typically cost between $10 and $30. Make sure you get the correct kit for your specific carburetor model (Walbro or Zama).
• Labor (If Hiring a Mechanic): If you’re not comfortable cleaning the carburetor yourself, a mechanic will likely charge between $50 and $150 for this service, depending on their hourly rate and the complexity of the job.

Data Point: According to a recent survey of small engine repair shops, the average cost of carburetor cleaning is $85.

My Insight: Don’t underestimate the power of a good cleaning. I’ve seen many saws brought back to life with just a thorough cleaning of the carburetor.

2. Fuel Line and Filter Inspection and Replacement

The Problem: Cracked or Clogged Fuel Lines and Filters

Fuel lines can crack and become brittle over time, especially if exposed to ethanol-blended fuels. A clogged fuel filter restricts fuel flow to the carburetor, leading to starting problems and stalling.

The Solution: Inspection and Replacement

Steps:

1. Inspect the Fuel Lines: Carefully inspect the fuel lines for cracks, leaks, or brittleness. Pay attention to the connections at the fuel tank and carburetor.
2. Replace Damaged Fuel Lines: If you find any damaged fuel lines, replace them with new ones. Use fuel line specifically designed for small engines.
3. Inspect the Fuel Filter: Locate the fuel filter inside the fuel tank. It’s usually attached to the end of the fuel line.
4. Replace the Fuel Filter: If the fuel filter is dirty or clogged, replace it with a new one.

Cost Considerations:

• Fuel Line: Fuel line typically costs between $2 and $5 per foot. You’ll likely need about 1-2 feet for the MS170.
• Fuel Filter: Fuel filters typically cost between $3 and $10.
• Labor (If Hiring a Mechanic): Replacing fuel lines and filters is a relatively simple task, so a mechanic will likely charge between $20 and $50 for this service.

Data Point: A study by the Outdoor Power Equipment Institute (OPEI) found that over 60% of small engine problems are related to fuel issues.

My Insight: I always recommend using high-quality fuel line and fuel filters. It’s a small investment that can save you a lot of headaches down the road. Also, always use fresh fuel! Stale fuel is a common culprit for starting problems. I use fuel stabilizer in all my gas cans.

3. Spark Plug Inspection and Replacement

The Problem: Fouled or Damaged Spark Plug

A fouled or damaged spark plug can prevent the engine from starting or running properly.

The Solution: Inspection and Replacement

Steps:

1. Remove the Spark Plug: Disconnect the spark plug wire and use a spark plug wrench to remove the spark plug.
2. Inspect the Spark Plug: Inspect the spark plug for fouling (carbon buildup), damage to the electrode, or cracks in the insulator.
3. Clean or Replace the Spark Plug: If the spark plug is fouled, you can try cleaning it with a wire brush. However, it’s generally best to replace it with a new one.
4. Gap the Spark Plug: Before installing the new spark plug, gap it to the correct specification. The correct gap for the MS170 is typically 0.020 inches (0.5 mm).
5. Install the Spark Plug: Install the spark plug and tighten it to the correct torque specification.

Cost Considerations:

• Spark Plug: A new spark plug typically costs between $3 and $10. The recommended spark plug for the MS170 is a Bosch WSR6F or NGK BPMR7A.
• Spark Plug Wrench: If you don’t already have one, a spark plug wrench will cost between $5 and $15.
• Labor (If Hiring a Mechanic): Replacing a spark plug is a very simple task, so a mechanic will likely charge a minimal fee (around $10-$20) if you’re already having other work done.

Data Point: According to a survey of small engine repair shops, spark plug replacement is one of the most common repairs performed.

My Insight: I always keep a spare spark plug on hand. It’s a quick and easy fix that can often get you back up and running in minutes.

4. Carburetor Adjustment: Fine-Tuning for Optimal Performance

The Problem: Incorrect Carburetor Settings

Even after cleaning the carburetor, the engine may not run properly if the carburetor settings are incorrect.

The Solution: Adjusting the “H” and “L” Screws

Steps:

1. Locate the “H” and “L” Screws: The “H” (high-speed) and “L” (low-speed) screws are typically located on the side of the carburetor.
2. Start with Factory Settings: Start with the factory settings (usually 1 turn out from fully closed for both screws).
3. Adjust the “L” Screw: Start the engine and let it warm up. Adjust the “L” screw until the engine idles smoothly without stalling. If the engine idles too fast, turn the “L” screw clockwise. If the engine stalls, turn the “L” screw counterclockwise.
4. Adjust the “H” Screw: With the engine running at full throttle, adjust the “H” screw until the engine runs smoothly without bogging down or surging. If the engine bogs down, turn the “H” screw counterclockwise. If the engine surges, turn the “H” screw clockwise.
5. Fine-Tune: Fine-tune the “H” and “L” screws until the engine runs smoothly at all speeds.

Cost Considerations:

• Screwdriver: You’ll need a small screwdriver to adjust the carburetor screws. If you don’t already have one, a set of screwdrivers will cost between $10 and $30.
• Tachometer (Optional): A tachometer can help you accurately adjust the carburetor settings. A small engine tachometer typically costs between $20 and $50. While not essential, it makes the process much easier.
• Labor (If Hiring a Mechanic): Carburetor adjustment is a relatively simple task, so a mechanic will likely charge between $20 and $50 for this service.

Data Point: Improper carburetor adjustment can reduce engine power by up to 20%.

My Insight: Carburetor adjustment can be a bit of an art. It takes practice and patience to get it just right. If you’re not comfortable adjusting the carburetor yourself, it’s best to consult a qualified mechanic. I’ve spent hours fiddling with carburetors, and sometimes, even I have to admit defeat and seek professional help.

5. Carburetor Replacement: When All Else Fails

The Problem: Irreparably Damaged Carburetor

If you’ve tried cleaning, adjusting, and repairing the carburetor, and the engine still won’t run properly, the carburetor may be irreparably damaged. This can happen due to corrosion, excessive wear, or internal damage.

The Solution: Replacing the Carburetor

Steps:

1. Purchase a New Carburetor: Purchase a new carburetor that is specifically designed for the Stihl MS170. Be sure to get the correct model (Walbro or Zama) for your saw.
2. Remove the Old Carburetor: Carefully disconnect the fuel lines and throttle linkage from the old carburetor. Unscrew the carburetor mounting bolts and remove the carburetor.
3. Install the New Carburetor: Install the new carburetor on the saw, reconnecting the fuel lines and throttle linkage.
4. Adjust the Carburetor: After replacing the carburetor, you’ll need to adjust the carburetor settings.

Cost Considerations:

• New Carburetor: A new carburetor for the Stihl MS170 typically costs between $20 and $80, depending on the brand and quality. Aftermarket carburetors are often cheaper than OEM (Original Equipment Manufacturer) carburetors.
• Labor (If Hiring a Mechanic): Replacing a carburetor is a relatively simple task, so a mechanic will likely charge between $50 and $150 for this service.

Data Point: The average lifespan of a carburetor is 5-10 years, depending on usage and maintenance.

My Insight: I’ve replaced quite a few carburetors over the years. Sometimes, it’s just not worth trying to repair a severely damaged carburetor. A new carburetor can often restore the engine to like-new performance. When replacing the carburetor, consider upgrading to an OEM part for better reliability and longevity.

Beyond the Carburetor: Other Potential Starting Problems

While the carburetor is often the culprit, other factors can also contribute to starting problems on the Stihl MS170. These include:

• Compression Issues: Low compression can prevent the engine from starting. This can be caused by worn piston rings, a damaged cylinder, or leaky valves.
• Ignition System Problems: A faulty ignition coil or spark plug wire can prevent the engine from firing.
• Air Leaks: Air leaks in the intake manifold or around the carburetor can disrupt the air-fuel mixture and cause starting problems.

Diagnosing these problems can be more complex and may require specialized tools and knowledge. If you’ve tried the carburetor fixes outlined above and the engine still won’t start, it’s best to consult a qualified mechanic.

Budgeting for Chainsaw Repairs: A Practical Guide

Now that we’ve covered the five essential carburetor fixes, let’s talk about budgeting for chainsaw repairs in general. Here’s a breakdown of the key cost factors and some tips for managing your expenses:

1. Preventative Maintenance: The Key to Cost Savings

The best way to save money on chainsaw repairs is to prevent them from happening in the first place. Here are some key preventative maintenance practices:

• Use Fresh Fuel: Always use fresh fuel and add fuel stabilizer to prevent fuel from going stale.
• Clean the Air Filter Regularly: A dirty air filter can restrict airflow and damage the engine.
• Sharpen the Chain Regularly: A dull chain puts extra strain on the engine and can lead to premature wear.
• Inspect the Chainsaw Regularly: Inspect the chainsaw for loose bolts, damaged parts, and leaks.
• Store the Chainsaw Properly: Store the chainsaw in a clean, dry place.

My Insight: I’ve found that spending a little time on preventative maintenance can save you a lot of money in the long run. It’s like changing the oil in your car – it’s a small investment that can prevent major problems down the road.

2. DIY vs. Hiring a Mechanic: Weighing the Pros and Cons

Deciding whether to tackle chainsaw repairs yourself or hire a mechanic is a crucial decision. Here’s a comparison of the pros and cons:

DIY:

• Pros:
  • Lower cost (you only pay for parts)
  • Greater control over the repair process
  • Opportunity to learn about your chainsaw
• Cons:
  • Requires technical knowledge and skills
  • Can be time-consuming
  • Risk of damaging the chainsaw if you’re not careful

Hiring a Mechanic:

• Pros:
  • Convenient and hassle-free
  • Ensures the repair is done correctly
  • Reduces the risk of damaging the chainsaw
• Cons:
  • Higher cost (you pay for labor in addition to parts)
  • Less control over the repair process

My Insight: If you’re comfortable working on small engines and have the necessary tools and knowledge, DIY repairs can save you a lot of money. However, if you’re not confident in your abilities, it’s best to hire a qualified mechanic.

3. Estimating Repair Costs: A Step-by-Step Approach

Here’s a step-by-step approach to estimating chainsaw repair costs:

1. Diagnose the Problem: Accurately diagnose the problem before you start buying parts.
2. Research Parts Costs: Research the cost of the necessary parts. Check prices at multiple retailers to find the best deal.
3. Estimate Labor Costs (If Hiring a Mechanic): Get an estimate from a mechanic before you commit to the repair.
4. Add a Contingency: Add a contingency of 10-20% to your estimate to cover unexpected expenses.

My Insight: It’s always a good idea to get multiple estimates from different mechanics before you commit to a repair. This will help you ensure that you’re getting a fair price.

4. Cost-Saving Tips: Stretching Your Repair Budget

Here are some additional cost-saving tips for chainsaw repairs:

• Buy Aftermarket Parts: Aftermarket parts are often cheaper than OEM parts. However, be sure to choose reputable brands to ensure quality and reliability.
• Shop Around for Parts: Check prices at multiple retailers to find the best deal.
• Consider Used Parts: If you’re on a tight budget, consider buying used parts from a reputable source.
• Do Some of the Work Yourself: Even if you’re hiring a mechanic, you can save money by doing some of the simpler tasks yourself, such as removing the air filter or spark plug.
• Negotiate with the Mechanic: Don’t be afraid to negotiate the price with the mechanic.

My Insight: I’ve saved a lot of money over the years by buying aftermarket parts and doing some of the work myself. However, it’s important to be careful when buying aftermarket parts to ensure that you’re getting a quality product.

5. Chainsaw Replacement vs. Repair: The Ultimate Decision

At some point, you may have to decide whether to repair your chainsaw or replace it with a new one. Here are some factors to consider:

• Cost of Repair: Compare the cost of repair to the cost of a new chainsaw.
• Age and Condition of the Chainsaw: Consider the age and condition of the chainsaw. If it’s old and worn out, it may not be worth repairing.
• Frequency of Repairs: If you’re constantly having to repair your chainsaw, it may be time to replace it.
• Your Needs: Consider your needs. If you’re using the chainsaw frequently, it may be worth investing in a new, more reliable model.

My Insight: I generally recommend repairing a chainsaw if the cost of repair is less than half the cost of a new chainsaw. However, if the chainsaw is old and worn out, or if you’re constantly having to repair it, it’s probably time to replace it.

• Average Hourly Rate for Small Engine Mechanics: According to the Bureau of Labor Statistics, the average hourly rate for small engine mechanics is $20-$40 per hour, depending on experience and location.
• Average Cost of Chainsaw Repair: According to a survey of small engine repair shops, the average cost of chainsaw repair is $100-$300, depending on the complexity of the repair.
• Average Lifespan of a Chainsaw: The average lifespan of a chainsaw is 5-10 years, depending on usage and maintenance.
• Fuel Costs: According to the Energy Information Administration, the average price of gasoline is $3-$5 per gallon, depending on location and season.
• Timber Prices: According to the USDA Forest Service, timber prices vary widely depending on species, quality, and location. The average price of sawtimber is $50-$200 per thousand board feet.
• Fuelwood Market Rates: The average price of firewood is $150-$300 per cord, depending on species, dryness, and location.

Actionable Takeaways and Next Steps

By now, you should have a solid understanding of how to diagnose and fix carburetor problems on your Stihl MS170, as well as how to budget for chainsaw repairs in general. Here are some actionable takeaways and next steps:

1. Diagnose the Problem: Carefully diagnose the problem before you start buying parts.
2. Try the Carburetor Fixes: Try the five essential carburetor fixes outlined in this article.
3. Estimate Repair Costs: Estimate the cost of repair before you commit to the project.
4. Decide DIY vs. Hiring a Mechanic: Decide whether to tackle the repair yourself or hire a mechanic.
5. Preventative Maintenance: Implement a preventative maintenance program to reduce the risk of future repairs.
6. Shop Around for Parts: Shop around for parts to find the best deal.
7. Negotiate with the Mechanic: Negotiate the price with the mechanic if you’re hiring one.
8. Consider Chainsaw Replacement: Consider replacing the chainsaw if the cost of repair is too high.

Conclusion: Mastering Your Chainsaw and Your Budget

The Stihl MS170 is a reliable and versatile tool, but like any piece of machinery, it requires regular maintenance and occasional repairs. By understanding the common carburetor problems, following the steps outlined in this article, and budgeting effectively, you can keep your MS170 running smoothly for years to come. Remember, a little knowledge and preventative maintenance can go a long way in saving you time, money, and frustration. Now, get out there and tackle those wood processing projects with confidence! And may your chainsaw always start on the first pull (or at least after a few)!

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