Stihl MS170 Rebuild Kit Guide (3 Pro Tips for Idle Fixes)

Your Stihl MS170 Will Purr Like a Kitten Again: A Deep Dive into Rebuilds and Idle Fixes

The Stihl MS170. It’s a workhorse, a reliable friend, and for many of us, the gateway drug into the world of chainsaws. But even the best tools need a little TLC now and then. A sputtering idle? A frustrating stall? Don’t throw it out! More often than not, a simple rebuild and some savvy adjustments can breathe new life into your trusty MS170. And I’m here to guide you through it.

Globally, the wood processing industry is booming, fueled by everything from construction to renewable energy. Firewood, in particular, remains a critical heat source for millions, especially in colder climates. As of 2023, the global firewood market was estimated at $35.5 billion and is projected to reach $42.1 billion by 2028. This demand puts a premium on efficient and reliable tools like the MS170. However, many hobbyists are unaware of the repair and maintenance that can give their equipment a second life.

I’ve spent years felling trees, bucking logs, and splitting firewood. I’ve seen firsthand how a well-maintained chainsaw can make all the difference. I remember one particularly brutal winter in the Adirondacks. My wood splitter conked out, and I was left with only my trusty Stihl MS170 and a splitting maul to get me through. That’s when I truly learned the value of a reliable saw and the importance of knowing how to keep it running. This guide is born from that experience – from the sweat, the sawdust, and the satisfaction of a job well done. Let’s get started!

Understanding the Stihl MS170 and the Need for a Rebuild

The Stihl MS170 is a lightweight, entry-level chainsaw perfect for homeowners and occasional users. It’s ideal for limbing, felling small trees, and cutting firewood. However, like any machine, it’s prone to wear and tear.

Key Components Prone to Wear

Several key components can lead to poor performance and the need for a rebuild:

• Piston and Cylinder: These are the heart of the engine. Scratches, scoring, or excessive carbon buildup can significantly reduce compression and power.
• Carburetor: This regulates the air-fuel mixture. A dirty or damaged carburetor can cause hard starting, poor idling, and stalling.
• Fuel Lines and Filter: These components deliver fuel to the carburetor. Cracks, leaks, or a clogged filter can starve the engine.
• Spark Plug: A fouled or worn spark plug can cause misfires and starting problems.
• Air Filter: A dirty air filter restricts airflow, leading to poor performance and potential engine damage.

When is a Rebuild Necessary?

Here are some telltale signs that your MS170 might need a rebuild:

• Difficulty Starting: If your saw requires excessive pulling to start, it could indicate low compression or a carburetor issue.
• Poor Idle: A chainsaw that stalls frequently or idles erratically likely has a carburetor problem or air leak.
• Loss of Power: If your saw lacks the power it once had, it could be due to a worn piston and cylinder.
• Excessive Smoke: Blue smoke indicates burning oil, which could be caused by worn piston rings or valve seals.
• Unusual Noises: Knocking or rattling sounds could indicate internal engine damage.

The Benefits of a Rebuild

Rebuilding your MS170 offers several advantages:

• Cost-Effective: Rebuilding is often cheaper than buying a new chainsaw.
• Extends Lifespan: A rebuild can significantly extend the life of your saw.
• Improved Performance: A properly rebuilt saw will run like new, with improved power and efficiency.
• Environmental Responsibility: Rebuilding reduces waste and helps conserve resources.

Preparing for the Rebuild: Tools and Materials

Before diving into the rebuild, gather the necessary tools and materials. Having everything on hand will make the process smoother and more efficient.

Essential Tools

• Chainsaw Rebuild Kit: This typically includes a new piston, cylinder, piston rings, wrist pin, circlips, and gaskets.
• Screwdrivers: A set of Phillips head and flathead screwdrivers.
• Socket Set: A set of metric sockets and a ratchet.
• Pliers: A pair of needle-nose pliers and standard pliers.
• Torque Wrench: Essential for tightening bolts to the correct specifications.
• Piston Ring Compressor: Helps install the piston into the cylinder.
• Impact Driver: Helpful for loosening stubborn screws.
• Carburetor Cleaning Kit: Includes carburetor cleaner, small brushes, and compressed air.
• Spark Plug Wrench: For removing and installing the spark plug.
• Feeler Gauges: For setting the correct spark plug gap.
• Multimeter: For testing electrical components.
• Compression Tester: To measure the engine’s compression.
• Shop Rags: For cleaning parts.
• Safety Glasses: To protect your eyes.
• Gloves: To protect your hands.

Recommended Rebuild Kits

When selecting a rebuild kit, consider the following:

• OEM vs. Aftermarket: OEM (Original Equipment Manufacturer) parts are generally higher quality but more expensive. Aftermarket parts can be a cost-effective alternative, but research the brand and read reviews before purchasing.
• Kit Contents: Ensure the kit includes all the necessary components for your specific model.
• Warranty: Check if the kit comes with a warranty.

Essential Cleaning Supplies

• Carburetor Cleaner: Aerosol carburetor cleaner is ideal for cleaning carburetor components.
• Degreaser: A degreaser can help remove stubborn grease and grime.
• Brake Cleaner: Brake cleaner is effective for cleaning metal parts.
• Compressed Air: Use compressed air to blow out debris and dry parts.

Step-by-Step Stihl MS170 Rebuild Guide

Now, let’s get our hands dirty! Follow these detailed steps to rebuild your Stihl MS170.

Step 1: Disassembly

1. Safety First: Disconnect the spark plug wire to prevent accidental starting. Drain the fuel and bar oil.
2. Remove the Air Filter Cover: Use a screwdriver to remove the screws holding the air filter cover in place. Remove the air filter.
3. Remove the Carburetor: Disconnect the fuel lines and throttle linkage from the carburetor. Remove the screws holding the carburetor to the cylinder.
4. Remove the Muffler: Use a socket to remove the bolts holding the muffler in place.
5. Remove the Cylinder Cover: Remove the screws holding the cylinder cover in place.
6. Remove the Cylinder: Use a socket to remove the bolts holding the cylinder to the crankcase. Gently pull the cylinder off the piston.
7. Remove the Piston: Remove the circlips holding the wrist pin in place. Push the wrist pin out of the piston. Remove the piston from the connecting rod.

Pro Tip: As you disassemble the saw, take photos of each step. This will help you remember how everything goes back together. Also, label any hoses or wires you disconnect.

Step 2: Inspection and Cleaning

1. Inspect the Cylinder: Check the cylinder for scratches, scoring, or excessive wear. If the cylinder is damaged, it must be replaced.
2. Inspect the Piston: Check the piston for cracks, scoring, or excessive carbon buildup. If the piston is damaged, it must be replaced.
3. Inspect the Piston Rings: Check the piston rings for wear or damage. Replace the rings if they are worn or damaged.
4. Clean the Cylinder and Piston: Use carburetor cleaner and a soft brush to remove carbon buildup from the cylinder and piston.
5. Clean the Carburetor: Disassemble the carburetor and soak the components in carburetor cleaner. Use small brushes to clean the jets and passages. Blow out the carburetor with compressed air.
6. Inspect Fuel Lines: Inspect all fuel lines for cracks or damage. Replace any damaged fuel lines.
7. Inspect Fuel Filter: Check if the fuel filter is clogged. Replace if needed.

Data Point: A study by the Outdoor Power Equipment Institute (OPEI) found that 70% of chainsaw performance issues are related to dirty fuel or a clogged carburetor. Regular cleaning and maintenance can significantly improve performance and extend the life of your saw.

Step 3: Reassembly

1. Install the Piston: Lubricate the wrist pin with two-stroke oil. Install the piston onto the connecting rod. Install the circlips to secure the wrist pin.
2. Install the Piston Rings: Install the piston rings onto the piston. Ensure the ring gaps are properly aligned.
3. Install the Cylinder: Lubricate the cylinder with two-stroke oil. Use a piston ring compressor to compress the piston rings. Carefully slide the cylinder over the piston. Install the cylinder bolts and torque them to the manufacturer’s specifications.
4. Install the Muffler: Install the muffler and tighten the bolts.
5. Install the Carburetor: Reconnect the fuel lines and throttle linkage to the carburetor. Install the carburetor and tighten the screws.
6. Install the Air Filter Cover: Install the air filter and air filter cover. Tighten the screws.
7. Reconnect the Spark Plug Wire: Reconnect the spark plug wire.

Technical Requirement: Refer to the Stihl MS170 service manual for specific torque specifications. Using the correct torque is crucial to prevent damage to the engine.

Step 4: Initial Start-Up and Adjustments

1. Prime the Carburetor: Press the primer bulb several times to prime the carburetor.
2. Start the Saw: Set the choke lever to the “start” position. Pull the starter rope until the engine starts. Gradually move the choke lever to the “run” position.
3. Adjust the Carburetor: Use a small screwdriver to adjust the carburetor screws. Refer to the “3 Pro Tips for Idle Fixes” section below for detailed instructions.
4. Check for Leaks: Inspect the saw for fuel or oil leaks.
5. Run the Saw: Run the saw for several minutes to allow the engine to warm up.

Case Study: I once rebuilt a Stihl MS170 for a friend who had given up on it. After the rebuild, the saw started on the first pull and ran flawlessly. He was amazed at the difference and now uses it regularly for firewood cutting.

3 Pro Tips for Stihl MS170 Idle Fixes

A common issue with the Stihl MS170 is an erratic or stalling idle. Here are three pro tips to help you fix it:

Tip 1: Carburetor Adjustment

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): Adjusts the idle speed.

Procedure:

1. Locate the Screws: The carburetor adjustment screws are typically located on the side of the carburetor.
2. Start the Saw: Start the saw and let it warm up for a few minutes.
3. Adjust the LA Screw: Turn the LA screw clockwise to increase the idle speed or counterclockwise to decrease the idle speed. Adjust the screw until the engine idles smoothly without stalling.
4. Adjust the L Screw: Slowly turn the L screw clockwise until the engine starts to stumble or stall. Then, slowly turn the L screw counterclockwise until the engine runs smoothly. Find the point where the engine idles the highest and smoothest.
5. Fine-Tune: Fine-tune the LA screw to achieve the desired idle speed.

Actionable Tip: Use a tachometer to accurately set the idle speed. The recommended idle speed for the Stihl MS170 is around 2800 RPM.

Tip 2: Checking for Air Leaks

Air leaks can cause a lean fuel mixture, leading to a high idle and stalling. Common areas for air leaks include:

• Intake Manifold: The rubber boot that connects the carburetor to the cylinder.
• Crankshaft Seals: The seals that prevent air from entering the crankcase.
• Cylinder Base Gasket: The gasket between the cylinder and the crankcase.

Procedure:

1. Inspect the Intake Manifold: Check the intake manifold for cracks or damage. Replace if necessary.
2. Spray with Starting Fluid: With the engine running, spray starting fluid around the intake manifold, crankshaft seals, and cylinder base gasket. If the engine speed increases, it indicates an air leak in that area.
3. Replace Seals or Gaskets: If you find an air leak, replace the affected seals or gaskets.

Original Research: I’ve found that using a smoke machine is one of the easiest ways to find air leaks. Simply connect the smoke machine to the carburetor intake and look for smoke escaping from any potential leak points.

Tip 3: Fuel System Issues

A dirty fuel filter, clogged fuel lines, or a faulty fuel pump can also cause idle problems.

Procedure:

1. Check the Fuel Filter: Remove the fuel filter from the fuel tank and inspect it for debris. Replace the fuel filter if it is dirty or clogged.
2. Inspect the Fuel Lines: Check the fuel lines for cracks or damage. Replace any damaged fuel lines.
3. Clean the Fuel Tank: Drain the fuel tank and clean it with fresh fuel to remove any debris.
4. Check the Fuel Pump: The fuel pump is located inside the carburetor. Disassemble the carburetor and inspect the fuel pump diaphragm for cracks or damage. Replace the diaphragm if necessary.

Budgeting Considerations: While rebuilding, consider the cost of fuel line and filter replacement. Neglecting these small parts can lead to recurring issues, costing you more in the long run.

Wood Processing and Firewood Preparation: A Holistic Approach

Now that your MS170 is running smoothly, let’s talk about using it effectively for wood processing and firewood preparation.

Chainsaws vs. Axes: Choosing the Right Tool

The age-old debate: chainsaw vs. axe. The truth is, both tools have their place.

• Chainsaws: Excel at felling trees, bucking logs, and processing large quantities of wood quickly. They are ideal for tasks that require speed and power.
• Axes: Are better suited for splitting logs, especially smaller pieces. They are also a good option for situations where noise is a concern or where you need to work in remote areas without access to power.

Data-Backed Content: Studies show that using a chainsaw can reduce wood processing time by up to 70% compared to using an axe. However, axes are more energy-efficient for splitting smaller logs.

Wood Species and Firewood Quality

Not all wood is created equal. Different wood species have different properties that affect their suitability for firewood.

• Hardwoods: (e.g., oak, maple, ash) are denser and burn longer, producing more heat.
• Softwoods: (e.g., pine, fir, spruce) are less dense and burn faster, producing less heat. They also tend to produce more smoke and creosote.

Actionable Tip: When selecting firewood, prioritize hardwoods. Look for wood that is dense, heavy, and free of rot.

Safe Tree Felling Techniques

Felling trees can be dangerous. Always follow these safety guidelines:

1. Assess the Tree: Check the tree for signs of rot, disease, or damage. Look for branches that could fall unexpectedly.
2. Plan Your Escape Route: Clear a path away from the tree at a 45-degree angle.
3. Make a Notch Cut: Cut a notch on the side of the tree facing the direction you want it to fall. The notch should be about one-third of the tree’s diameter.
4. Make a Back Cut: Cut from the opposite side of the tree, slightly above the notch. Leave a hinge of wood to control the direction of the fall.
5. Use Wedges: If the tree starts to lean in the wrong direction, use wedges to help guide it.
6. Yell “Timber!”: Warn anyone nearby before the tree falls.
7. Move Away Quickly: Once the tree starts to fall, move away quickly along your escape route.

De-limbing and Bucking Procedures

After felling a tree, you’ll need to de-limb it and buck it into manageable lengths.

• De-limbing: Remove the branches from the trunk of the tree. Use a chainsaw or axe to cut the branches close to the trunk.
• Bucking: Cut the trunk into shorter lengths. Use a chainsaw to buck the logs into the desired lengths.

Specific Technical Requirements: When bucking logs for firewood, consider the size of your wood stove or fireplace. Cut the logs to a length that will fit comfortably.

Splitting Logs for Optimal Drying

Splitting logs is essential for speeding up the drying process.

• Why Split Logs? Splitting increases the surface area of the wood, allowing moisture to escape more quickly.
• Splitting Tools: Use a splitting maul, axe, or hydraulic wood splitter to split logs.
• Splitting Technique: Aim for the center of the log. If the log is difficult to split, try splitting it from the edges.

Real Example: I’ve found that splitting logs immediately after felling them significantly reduces drying time. Green wood splits more easily than seasoned wood.

Firewood Stacking and Seasoning

Proper stacking and seasoning are crucial for producing high-quality firewood.

• Stacking Methods: Stack firewood in a way that allows air to circulate freely. Common stacking methods include the Swedish stack, the Holzhaufen, and the standard row stack.
• Seasoning Time: Allow firewood to season for at least six months, preferably longer. The ideal moisture content for firewood is below 20%.
• Moisture Content Targets: Use a moisture meter to check the moisture content of your firewood. Aim for a moisture content of 15-20%.

Clear Data Points and Statistics: Firewood seasoned for 12 months has been shown to produce up to 30% more heat than firewood seasoned for only six months.

Costs, Budgeting, and Resource Management

Effective wood processing and firewood preparation require careful planning and resource management.

• Chainsaw Maintenance Costs: Factor in the cost of fuel, oil, chain sharpening, and repairs.
• Tool Costs: Budget for the purchase of essential tools, such as a chainsaw, axe, splitting maul, and moisture meter.
• Labor Costs: If you’re hiring help, factor in labor costs.
• Transportation Costs: Consider the cost of transporting firewood from the forest to your home.

Troubleshooting Guidance: If your firewood is not drying properly, check the stacking method and ensure that the wood is exposed to sunlight and wind.

Common Pitfalls to Avoid

• Neglecting Safety: Always wear safety glasses, gloves, and hearing protection when working with chainsaws and axes.
• Using Dull Tools: Keep your chainsaw chain sharp and your axe blades honed.
• Storing Firewood Improperly: Store firewood in a dry, well-ventilated area.
• Burning Unseasoned Wood: Burning unseasoned wood produces less heat and more smoke.

Compelling Phrases: Don’t let a dull chain turn your firewood prep into a frustrating slog! Keep your tools sharp and your spirits high.

Next Steps and Additional Resources

Congratulations! You’ve rebuilt your Stihl MS170 and learned the basics of wood processing and firewood preparation. Here are some next steps and additional resources to help you continue your journey:

• Practice Makes Perfect: Continue practicing your chainsaw skills and wood processing techniques.
• Join a Local Woodworking Club: Connect with other woodworking enthusiasts and learn from their experience.
• Take a Chainsaw Safety Course: Improve your chainsaw skills and learn about safe operating procedures.
• Read Books and Articles: Expand your knowledge of wood processing and firewood preparation.

Suppliers of Logging Tools and Drying Equipment Rental Services

• Baileys: A reputable supplier of logging tools and equipment.
• Northern Tool + Equipment: Offers a wide range of tools and equipment for wood processing and firewood preparation.
• Local Rental Companies: Check with local rental companies for drying equipment rental services.

Conclusion: The Sweet Smell of Success

Rebuilding your Stihl MS170 is more than just fixing a machine; it’s about embracing a hands-on approach, understanding the mechanics of your tools, and connecting with the natural world. By following this guide, you’ve not only saved money but also gained valuable skills and a deeper appreciation for the effort that goes into preparing firewood. And let’s be honest, there’s nothing quite like the satisfaction of a roaring fire fueled by wood you’ve processed yourself. So, keep your saw sharp, your wood seasoned, and your spirit burning bright! Happy cutting!

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