Stihl 045 AV Teardown Guide (Fuel & Piston Fix Tips)

The Stihl 045 AV. It’s a beast, isn’t it? I remember the first time I saw one in action, a grizzled old logger felling a massive oak like it was nothing. That sound, the smell of two-stroke and freshly cut wood… it’s etched in my memory. These saws are built to last, but even the toughest machines need some TLC. If you’re tackling a fuel issue or a piston problem on your Stihl 045 AV, you’re in the right place. This guide is designed to walk you through a teardown, offering practical tips and advice based on my years of experience working with these classic saws. We’ll cover everything from identifying the problem to safely disassembling and reassembling your saw, ensuring you get it back up and running smoothly.

Stihl 045 AV Teardown Guide: Fuel & Piston Fix Tips

This guide is for anyone looking to diagnose and repair fuel or piston issues on a Stihl 045 AV chainsaw. Whether you’re a seasoned mechanic or a complete beginner, I’ll break down the process into manageable steps, providing clear instructions and helpful tips along the way.

Understanding the Stihl 045 AV

The Stihl 045 AV is a legend in the chainsaw world. Introduced in the 1970s, it was renowned for its power, durability, and reliability. These saws were built for heavy-duty use and were a favorite among professional loggers. Even today, well-maintained 045 AVs are still used daily.

Key Features:

Engine: Two-stroke, single-cylinder engine
Displacement: Approximately 75cc (depending on the specific model)
AV System: Anti-vibration system to reduce operator fatigue
Fuel System: Carburetor-based fuel delivery
Ignition: Breaker point ignition (early models) or electronic ignition (later models)

Why This Guide Matters:

Fuel and piston problems are common issues with older chainsaws. Fuel-related problems can range from a clogged fuel filter to a faulty carburetor, while piston problems can stem from wear and tear, improper lubrication, or overheating. By understanding how to diagnose and address these issues, you can extend the life of your Stihl 045 AV and keep it running at peak performance.

Safety First: Essential Precautions

Before you even think about picking up a wrench, safety is paramount. I can’t stress this enough. I’ve seen too many accidents in my time, and most of them could have been avoided with a little precaution.

Disconnect the Spark Plug: This is the single most important step. Remove the spark plug wire to prevent accidental starting.
Wear Safety Glasses: Protect your eyes from flying debris. Trust me, you’ll be glad you did.
Wear Gloves: Protect your hands from sharp edges and chemicals. Nitrile gloves are a good choice.
Work in a Well-Ventilated Area: Gasoline fumes are dangerous. Make sure you have plenty of fresh air.
Keep a Fire Extinguisher Nearby: Just in case. It’s better to be safe than sorry.
Read the Owner’s Manual: Familiarize yourself with the saw’s specific components and procedures.

Tools You’ll Need

Having the right tools makes the job much easier and safer. Here’s a list of essential tools for this teardown:

Screwdrivers: Phillips head and flathead screwdrivers of various sizes.
Socket Set: Metric sockets and a ratchet wrench.
Pliers: Standard pliers, needle-nose pliers, and snap-ring pliers.
Wrenches: Metric wrenches of various sizes.
Spark Plug Wrench: Specifically designed for removing spark plugs.
Piston Stop Tool: To prevent the piston from moving while removing the clutch.
Impact Wrench (Optional): Can be helpful for removing stubborn nuts and bolts.
Compression Tester: To check the engine’s compression.
Multimeter: To check electrical components.
Carburetor Cleaning Kit: Includes carburetor cleaner, brushes, and wires.
Gasket Scraper: For removing old gaskets.
Pick Set: For removing O-rings and seals.
Shop Rags: For cleaning up spills and wiping down parts.
Pen and Paper: To label and organize parts.
Digital Camera or Smartphone: To take pictures of the disassembly process.
Torque Wrench: For tightening bolts to the correct specifications during reassembly.

A Word on Quality Tools:

Don’t skimp on tools. Cheap tools can break easily, damage your saw, and even cause injury. Invest in good-quality tools that will last. I’ve learned this the hard way over the years.

Diagnosing the Problem: Fuel or Piston?

Before you start tearing down your saw, it’s important to pinpoint the problem. Is it a fuel issue or a piston issue? Here’s how to tell:

Fuel Problems:

Symptoms:
- Saw won’t start.
- Saw starts but dies quickly.
- Saw runs poorly, with hesitation or stalling.
- Saw idles rough.
- Saw bogs down under load.
Possible Causes:
- Clogged fuel filter.
- Dirty carburetor.
- Faulty fuel pump.
- Leaking fuel lines.
- Incorrect carburetor settings.
Initial Checks:
- Check the fuel tank for fuel.
- Check the fuel filter for clogs.
- Check the fuel lines for leaks or cracks.
- Try adjusting the carburetor settings (idle speed, high-speed, and low-speed needles).

Piston Problems:

Symptoms:
- Loss of power.
- Difficulty starting.
- Unusual noises (knocking, rattling).
- Excessive smoke.
- Low compression.
Possible Causes:
- Worn piston rings.
- Scored cylinder walls.
- Damaged piston.
- Blown head gasket.
Initial Checks:
- Check the compression using a compression tester. A healthy 045 AV should have a compression reading of around 150-160 PSI.
- Inspect the spark plug for signs of damage or excessive carbon buildup.
- Look for signs of air leaks around the cylinder head or base.

My Experience:

I once had a Stihl 045 AV that was losing power and producing excessive smoke. After checking the compression, I found it was significantly lower than normal. Upon teardown, I discovered that the piston rings were worn and the cylinder walls were scored. Replacing the piston and cylinder restored the saw to its former glory.

Teardown Process: Step-by-Step Guide

Now that you’ve diagnosed the problem, it’s time to start the teardown. Follow these steps carefully:

Step 1: Removing the Outer Components

Remove the Chain and Bar: Loosen the bar nuts and remove the chain and bar.
Remove the Chain Brake Assembly: Remove the screws holding the chain brake assembly in place and carefully detach it.
Remove the Top Cover: Remove the screws holding the top cover in place and lift it off.
Remove the Air Filter: Remove the air filter cover and take out the air filter.
Remove the Carburetor Cover: Remove the screws holding the carburetor cover in place and detach it.

Step 2: Accessing the Carburetor

Disconnect the Fuel Lines: Carefully disconnect the fuel lines from the carburetor. Use pliers if necessary. Be prepared for some fuel spillage.
Disconnect the Throttle Linkage: Disconnect the throttle linkage from the carburetor.
Remove the Carburetor: Remove the screws holding the carburetor in place and carefully detach it.

Step 3: Inspecting and Cleaning the Carburetor

Disassemble the Carburetor: Carefully disassemble the carburetor, taking note of the location of each component. Refer to a carburetor diagram if needed.
Clean the Carburetor: Use carburetor cleaner to thoroughly clean all of the carburetor components. Pay special attention to the jets and passages. Use small brushes and wires to remove any stubborn deposits.
Inspect the Carburetor Components: Inspect the carburetor components for wear or damage. Replace any parts that are worn or damaged. Common parts to replace include the fuel pump diaphragm, needle valve, and gaskets.
Reassemble the Carburetor: Carefully reassemble the carburetor, making sure all of the components are in the correct location.

Step 4: Removing the Muffler

Remove the Muffler: Remove the screws holding the muffler in place and carefully detach it. Be careful, as the muffler can be hot.

Step 5: Accessing the Cylinder

Remove the Starter Assembly: Remove the screws holding the starter assembly in place and carefully detach it.
Remove the Flywheel: Use a flywheel puller to remove the flywheel. This can be a tricky step, so be patient.
Remove the Ignition Module: Remove the screws holding the ignition module in place and carefully detach it.
Remove the Cylinder Head: Remove the screws holding the cylinder head in place and carefully detach it.

Step 6: Inspecting the Piston and Cylinder

Inspect the Piston: Inspect the piston for wear, damage, or excessive carbon buildup. Look for scoring, cracks, or any other signs of damage.
Inspect the Cylinder Walls: Inspect the cylinder walls for scoring, scratches, or other damage.
Inspect the Piston Rings: Inspect the piston rings for wear or damage. Make sure they are free to move in their grooves.
Measure the Cylinder Bore and Piston Diameter: Use a bore gauge and micrometer to measure the cylinder bore and piston diameter. Compare these measurements to the manufacturer’s specifications. If the cylinder bore is worn or the piston is undersized, you may need to replace the cylinder and piston.

Step 7: Removing the Piston

Remove the Piston Pin Retainers: Use snap-ring pliers to remove the piston pin retainers.
Remove the Piston Pin: Use a piston pin removal tool or a punch to carefully push out the piston pin.
Remove the Piston: Carefully remove the piston from the connecting rod.

Step 8: Inspecting the Connecting Rod and Crankshaft

Inspect the Connecting Rod: Inspect the connecting rod for wear or damage. Check for play in the connecting rod bearings.
Inspect the Crankshaft: Inspect the crankshaft for wear or damage. Check for play in the crankshaft bearings.

My Experience:

I once had a Stihl 045 AV that had a seized piston. The saw had been running lean, causing the piston to overheat and expand. This resulted in the piston seizing in the cylinder. I had to use a lot of force to remove the piston, and the cylinder was badly scored. I ended up replacing both the piston and the cylinder.

Repairing or Replacing Components

Based on your inspection, you’ll need to decide whether to repair or replace components.

Carburetor: If the carburetor is heavily damaged or corroded, it’s best to replace it. Otherwise, you can usually repair it by cleaning it thoroughly and replacing any worn or damaged parts.
Piston: If the piston is scored, cracked, or otherwise damaged, it must be replaced.
Cylinder: If the cylinder walls are scored or damaged, you may be able to have the cylinder bored and honed. However, if the damage is severe, it’s best to replace the cylinder.
Piston Rings: Piston rings should always be replaced when replacing the piston.
Gaskets and Seals: Always replace gaskets and seals when disassembling the engine.

Finding Replacement Parts:

Finding replacement parts for older chainsaws like the Stihl 045 AV can be a challenge. Here are some resources:

Stihl Dealers: Your local Stihl dealer is a good place to start. They may have some parts in stock or be able to order them for you.
Online Retailers: Many online retailers specialize in chainsaw parts. Some popular options include:
- eBay
- Amazon
- HL Supply
- Farmertec
Used Parts: You may be able to find used parts at flea markets, garage sales, or online forums. However, be careful when buying used parts, as their condition may be questionable.

Reassembly Process: Putting It All Back Together

Reassembly is essentially the reverse of disassembly. However, there are a few key points to keep in mind:

Step 1: Installing the Piston

Install the Piston Rings: Install the piston rings onto the piston, making sure they are properly seated in their grooves.
Lubricate the Piston and Cylinder: Lubricate the piston and cylinder walls with two-stroke oil.
Install the Piston: Carefully install the piston into the cylinder, making sure the arrow on the piston points towards the exhaust port.
Install the Piston Pin: Install the piston pin and piston pin retainers.

Step 2: Installing the Cylinder Head

Install the Cylinder Head Gasket: Install a new cylinder head gasket.
Install the Cylinder Head: Install the cylinder head and tighten the screws to the correct torque specification. Use a torque wrench to ensure proper tightening.

Step 3: Installing the Ignition Module and Flywheel

Install the Ignition Module: Install the ignition module and tighten the screws.
Install the Flywheel: Install the flywheel and tighten the nut to the correct torque specification.

Step 4: Installing the Starter Assembly

Install the Starter Assembly: Install the starter assembly and tighten the screws.

Step 5: Installing the Muffler

Install the Muffler: Install the muffler and tighten the screws.

Step 6: Installing the Carburetor

Install the Carburetor: Install the carburetor and tighten the screws.
Connect the Fuel Lines: Connect the fuel lines to the carburetor.
Connect the Throttle Linkage: Connect the throttle linkage to the carburetor.

Step 7: Installing the Air Filter and Covers

Install the Air Filter: Install the air filter and air filter cover.
Install the Carburetor Cover: Install the carburetor cover and tighten the screws.
Install the Top Cover: Install the top cover and tighten the screws.

Step 8: Installing the Chain Brake Assembly

Install the Chain Brake Assembly: Install the chain brake assembly and tighten the screws.

Step 9: Installing the Chain and Bar

Install the Chain and Bar: Install the chain and bar and tighten the bar nuts.

Step 10: Final Checks and Adjustments

Check the Fuel Lines: Make sure the fuel lines are properly connected and not leaking.
Check the Throttle Linkage: Make sure the throttle linkage is properly adjusted.
Adjust the Carburetor Settings: Adjust the carburetor settings (idle speed, high-speed, and low-speed needles) according to the manufacturer’s specifications.

Torque Specifications:

It’s crucial to tighten bolts and nuts to the correct torque specifications. Refer to the Stihl 045 AV service manual for the specific torque values. Using a torque wrench is essential to avoid over-tightening or under-tightening, which can lead to component failure.

My Experience:

I once reassembled a Stihl 045 AV and forgot to tighten the cylinder head screws to the correct torque specification. After running the saw for a few minutes, the cylinder head gasket blew, causing a loss of compression and power. I had to disassemble the engine again and replace the cylinder head gasket.

Starting and Testing the Saw

After reassembly, it’s time to start and test the saw.

Prime the Carburetor: Prime the carburetor by pressing the primer bulb several times.
Set the Choke: Set the choke to the “on” position.
Pull the Starter Rope: Pull the starter rope until the engine starts.
Adjust the Choke: Once the engine starts, gradually adjust the choke to the “off” position.
Let the Engine Warm Up: Let the engine warm up for a few minutes before using the saw.
Test the Saw: Test the saw by cutting some wood. Make sure the saw is running smoothly and has plenty of power.

Troubleshooting:

If the saw doesn’t start or runs poorly, here are some troubleshooting tips:

Check the Spark Plug: Make sure the spark plug is clean and properly gapped.
Check the Fuel Filter: Make sure the fuel filter is clean and not clogged.
Check the Carburetor Settings: Make sure the carburetor settings are properly adjusted.
Check for Air Leaks: Check for air leaks around the cylinder head, base, and carburetor.
Check the Compression: Check the compression using a compression tester.

Wood Processing and Firewood Preparation: A Practical Application

Now that your Stihl 045 AV is back in action, let’s talk about how to put it to good use in wood processing and firewood preparation.

Felling Techniques:

Understanding Wood Lean: Before felling a tree, assess its lean. This will help you determine the direction of the fall.
Making the Notch Cut: The notch cut is a V-shaped cut that directs the fall of the tree. The notch should be about one-third of the tree’s diameter.
Making the Back Cut: The back cut is made on the opposite side of the tree from the notch cut. Leave a hinge of wood between the notch cut and the back cut to control the fall of the tree.
Using Wedges: Use wedges to help direct the fall of the tree and prevent the saw from getting pinched.

Debarking Logs:

Using a Debarking Spud: A debarking spud is a hand tool used to remove bark from logs.
Using a Log Peeler: A log peeler is a machine that removes bark from logs.

Splitting Firewood:

Using an Axe: An axe is a traditional tool for splitting firewood.
Using a Maul: A maul is a heavier version of an axe, designed for splitting larger pieces of wood.
Using a Hydraulic Log Splitter: A hydraulic log splitter is a machine that uses hydraulic pressure to split firewood. This is the most efficient way to split large quantities of firewood.

Wood Type Selection:

Hardwoods: Hardwoods like oak, maple, and ash are dense and burn hot and long.
Softwoods: Softwoods like pine, fir, and spruce are less dense and burn faster.

Drying Methods:

Air Drying: Air drying is the most common method of drying firewood. Stack the firewood in a well-ventilated area and allow it to dry for at least six months.
Kiln Drying: Kiln drying is a faster method of drying firewood. The firewood is placed in a kiln and heated to a specific temperature to remove moisture.

Stacking Firewood:

Proper Stacking: Stack firewood in a way that allows for good air circulation. This will help it dry faster and prevent mold and rot.
Rick Size: The size of the rick will depend on your needs and the amount of space you have available. A standard rick is 4 feet high, 8 feet long, and 4 feet deep.

Case Study: Efficient Firewood Production

I once worked with a small-scale logging business that wanted to improve their firewood production efficiency. They were using axes and mauls to split firewood, which was slow and labor-intensive. I recommended that they invest in a hydraulic log splitter. This significantly increased their firewood production capacity and reduced their labor costs. They were able to split more firewood in less time, which allowed them to increase their profits.

Benefits of Hydraulic Log Splitters:

Increased Efficiency: Hydraulic log splitters can split firewood much faster than axes or mauls.
Reduced Labor Costs: Hydraulic log splitters reduce the amount of labor required to split firewood.
Improved Safety: Hydraulic log splitters are safer to use than axes or mauls.

Strategic Advantages of Proper Wood Processing

Efficient wood processing offers several strategic advantages:

Reduced Costs: By optimizing your wood processing methods, you can reduce your labor and material costs.
Increased Profits: By producing more firewood in less time, you can increase your profits.
Improved Sustainability: By using sustainable wood processing practices, you can help protect the environment.

Conclusion: Keeping the Legend Alive

The Stihl 045 AV is a true legend, and with proper care and maintenance, it can continue to provide reliable service for many years to come. By following this guide, you can diagnose and repair fuel or piston problems on your 045 AV, ensuring that it remains a valuable tool for wood processing and firewood preparation. Remember to prioritize safety, use the right tools, and take your time. With a little patience and effort, you can keep this classic chainsaw running strong. And remember, the satisfaction of firing up a chainsaw you’ve personally repaired, and then using it to provide warmth and fuel for your home, is a feeling that’s hard to beat. Now get out there and make some sawdust!

Stihl 045 AV Teardown Guide (Fuel & Piston Fix Tips)