Stihl BG55 Carburetor Issues Solved (5 Expert Tuning Tips)

Ah, the Stihl BG55 blower. A trusty tool for clearing leaves and debris, until it isn’t. More often than not, when that little engine starts acting up, the culprit is the carburetor. I’ve spent countless hours wrestling with these carburetors, and I’m here to share my hard-earned wisdom. We’re going to dive deep into diagnosing and resolving those frustrating Stihl BG55 carburetor issues, with five expert tuning tips to get your blower roaring back to life. Let’s get started and get that blower back in action!

Stihl BG55 Carburetor Issues Solved (5 Expert Tuning Tips)

Understanding the Heart of the Matter: The Carburetor

Before we start wrenching, let’s understand what we’re dealing with. The carburetor is the heart of your BG55, responsible for mixing air and fuel in the correct ratio for combustion. When it’s not working correctly, you’ll experience a range of problems, from difficulty starting to poor performance or even stalling. I’ve seen everything from gummy residue clogging the tiny passages to damaged diaphragms causing havoc. Understanding the basics will make troubleshooting and tuning much easier.

Common Symptoms of a Carburetor Problem

Knowing the symptoms is half the battle. Here are some of the most common signs that your BG55’s carburetor is in trouble:

Difficulty Starting: The engine cranks but refuses to fire up. This often indicates a fuel delivery problem.
Rough Idling: The engine idles unevenly or stalls frequently. This can be due to a lean or rich fuel mixture.
Poor Performance: The blower lacks power, especially under load. This could be caused by a clogged carburetor or incorrect fuel mixture.
Stalling: The engine stalls after running for a short period. Overheating can also cause stalling, but carburetor issues are a frequent cause.
Flooding: The engine is flooded with fuel, making it difficult to start. This is often due to a stuck needle valve or incorrect carburetor settings.

I remember one particularly frustrating afternoon when my BG55 refused to start no matter what I tried. After hours of fiddling, I discovered a tiny piece of debris lodged in the main jet. It’s always the little things, isn’t it?

Essential Tools for Carburetor Work

Before you start, gather the right tools. Having the proper equipment will make the job much easier and prevent damage to the carburetor.

Screwdrivers: A set of small screwdrivers, including a carburetor adjustment tool (splined or D-shaped), is essential.
Carburetor Cleaner: A good quality carburetor cleaner is crucial for removing varnish and deposits.
Compressed Air: Use compressed air to blow out the carburetor passages after cleaning.
Pliers: Needle-nose pliers are helpful for removing small parts.
Socket Set: Needed for removing the air filter housing and other components.
New Fuel Filter: Replace the fuel filter while you’re at it. A clean fuel filter prevents debris from clogging the carburetor.
New Spark Plug: A new spark plug ensures proper ignition.
Carburetor Rebuild Kit (Optional): If the carburetor is heavily worn or damaged, a rebuild kit is a good investment.
Safety Glasses: Always wear safety glasses to protect your eyes from debris and chemicals.
Gloves: Wear gloves to protect your hands from fuel and chemicals.

I always keep a well-stocked toolbox specifically for small engine repairs. It saves me time and frustration in the long run.

Step-by-Step Guide to Cleaning the Stihl BG55 Carburetor

Cleaning the carburetor is often the first step in resolving carburetor issues. Over time, fuel can break down and leave behind varnish and deposits that clog the tiny passages in the carburetor. Here’s how to clean it properly:

1. Remove the Air Filter and Housing

Start by removing the air filter cover and the air filter itself. Then, remove the air filter housing. This will expose the carburetor. I find that a socket wrench makes quick work of these steps.

2. Disconnect the Fuel Lines and Throttle Linkage

Carefully disconnect the fuel lines from the carburetor. Use pliers to gently squeeze the fuel line clamps and pull the lines off. Be prepared for some fuel spillage, so have a rag handy. Disconnect the throttle linkage by gently prying it off the carburetor arm.

3. Remove the Carburetor

Unbolt the carburetor from the engine. The carburetor is usually held in place by two bolts. Once the bolts are removed, gently pull the carburetor away from the engine.

4. Disassemble the Carburetor

Disassemble the carburetor carefully. Remove the fuel bowl, needle valve, and jets. Pay attention to the order in which the parts are removed, as you’ll need to reassemble them in the same order. I like to take pictures with my phone as I disassemble things – it’s a lifesaver when it’s time to put everything back together.

5. Clean the Carburetor Parts

Spray all the carburetor parts with carburetor cleaner. Use a small brush to scrub away any stubborn deposits. Pay particular attention to the jets and the needle valve. Make sure all the passages are clear.

6. Blow Out the Passages with Compressed Air

Use compressed air to blow out all the passages in the carburetor body. This will remove any remaining debris and ensure that the passages are clear. I usually wear safety glasses during this step to protect my eyes from flying debris.

7. Reassemble the Carburetor

Reassemble the carburetor in the reverse order of disassembly. Make sure all the parts are properly seated and tightened.

8. Reinstall the Carburetor

Reinstall the carburetor onto the engine. Connect the fuel lines and throttle linkage. Make sure the fuel lines are securely attached and the throttle linkage moves freely.

9. Reinstall the Air Filter Housing and Air Filter

Reinstall the air filter housing and air filter. Make sure the air filter is clean and properly seated.

10. Test the Engine

Start the engine and test its performance. If the engine still runs poorly, you may need to adjust the carburetor settings.

Takeaway: Cleaning the carburetor can often resolve many common issues. Always take your time and pay attention to detail during the disassembly and reassembly process.

Expert Tuning Tip #1: Understanding the Carburetor Adjustment Screws

The Stihl BG55 carburetor typically has two adjustment screws: the “H” (high-speed) and “L” (low-speed) screws. These screws control the fuel mixture at different engine speeds. Adjusting these screws correctly is crucial for optimal performance. I can’t tell you how many times I’ve seen people randomly turning these screws without understanding what they’re doing, only to make things worse.

The “L” Screw: This screw controls the fuel mixture at idle and low speeds. Adjusting this screw affects the engine’s ability to idle smoothly and transition to higher speeds.
The “H” Screw: This screw controls the fuel mixture at high speeds. Adjusting this screw affects the engine’s power output and prevents the engine from running too lean or too rich at high speeds.

Important Note: Some Stihl BG55 carburetors have limiter caps on the adjustment screws. These caps restrict the range of adjustment to meet emissions regulations. If your carburetor has limiter caps, you may need to remove them to make more significant adjustments. I’ll cover that process later.

Expert Tuning Tip #2: The Initial Carburetor Settings

Before you start fine-tuning, it’s essential to set the carburetor to its initial settings. These settings provide a baseline for further adjustments. The initial settings for the Stihl BG55 carburetor are typically:

“L” Screw: Turn the “L” screw clockwise until it is gently seated, then back it out 1 to 1 1/2 turns.
“H” Screw: Turn the “H” screw clockwise until it is gently seated, then back it out 1 to 1 1/2 turns.

These are just starting points. You’ll likely need to fine-tune the settings to achieve optimal performance. I always recommend starting with these settings and then making small adjustments based on how the engine is running.

Expert Tuning Tip #3: Fine-Tuning the “L” Screw for Optimal Idle

The “L” screw is critical for achieving a smooth and stable idle. Here’s how to fine-tune it:

Start the Engine: Start the engine and let it warm up for a few minutes.
Adjust the “L” Screw: Turn the “L” screw slowly clockwise or counterclockwise until the engine idles smoothly.
Listen to the Engine: Listen carefully to the engine’s idle. If the idle is too high, the engine may be running lean. If the idle is too low or the engine stalls, it may be running rich.
Find the Sweet Spot: The goal is to find the “sweet spot” where the engine idles smoothly without stalling or running too fast.
Test the Throttle Response: After adjusting the “L” screw, test the throttle response. The engine should transition smoothly from idle to higher speeds without hesitation.

I often find that a slight adjustment to the “L” screw can make a big difference in the engine’s overall performance. Patience is key.

Example: I was recently working on a BG55 that was stalling frequently at idle. After adjusting the “L” screw, I found that the engine idled smoothly and the throttle response was much improved. The final setting was about 1 1/4 turns out from seated.

Expert Tuning Tip #4: Fine-Tuning the “H” Screw for Maximum Power

The “H” screw controls the fuel mixture at high speeds. Adjusting this screw correctly is essential for achieving maximum power and preventing engine damage. Here’s how to fine-tune it:

Run the Engine at Full Throttle: Run the engine at full throttle for a few seconds.
Adjust the “H” Screw: Turn the “H” screw slowly clockwise or counterclockwise until the engine runs smoothly and produces maximum power.
Listen to the Engine: Listen carefully to the engine. If the engine sounds raspy or strained, it may be running lean. If the engine sounds muffled or sluggish, it may be running rich.
Find the Sweet Spot: The goal is to find the “sweet spot” where the engine runs smoothly and produces maximum power without running too lean or too rich.
Check the Spark Plug: After adjusting the “H” screw, check the spark plug. A light tan color indicates a proper fuel mixture. A white or gray color indicates a lean mixture, while a black or sooty color indicates a rich mixture.

Important Note: Running the engine too lean can cause serious damage, such as piston seizure. Always err on the side of running slightly rich. I always advise adjusting the “H” screw in small increments and monitoring the engine’s performance closely.

Example: I once worked on a BG55 that was lacking power at high speeds. After adjusting the “H” screw, I found that the engine ran much stronger and the spark plug color was a perfect tan. The final setting was about 1 3/8 turns out from seated.

Expert Tuning Tip #5: Removing Limiter Caps for More Precise Adjustments

As mentioned earlier, some Stihl BG55 carburetors have limiter caps on the adjustment screws. These caps restrict the range of adjustment to meet emissions regulations. If you need to make more significant adjustments, you may need to remove these caps. Here’s how:

Locate the Limiter Caps: The limiter caps are typically small plastic caps that fit over the adjustment screws.
Remove the Caps: Use a small screwdriver or pick to carefully pry the caps off the adjustment screws. Be careful not to damage the screws or the carburetor body.
Make Adjustments: Once the caps are removed, you can make more precise adjustments to the “L” and “H” screws.

Important Note: Removing the limiter caps may violate emissions regulations in some areas. Check your local regulations before removing the caps.

My Experience: I’ve removed limiter caps on several BG55 carburetors and found that it allows for much more precise adjustments. However, it’s essential to understand the potential consequences and make adjustments carefully.

Troubleshooting Common Carburetor Problems

Even with careful cleaning and tuning, you may still encounter carburetor problems. Here are some common issues and how to troubleshoot them:

Engine Won’t Start:
- Check the Fuel Supply: Make sure there is fuel in the tank and the fuel filter is clean.
- Check the Spark Plug: Make sure the spark plug is clean and properly gapped.
- Check for Spark: Use a spark tester to check for spark. If there is no spark, the ignition coil may be faulty.
- Check the Carburetor: Make sure the carburetor is clean and the jets are not clogged.
- Engine Runs Rough at Idle:
- Adjust the “L” Screw: Fine-tune the “L” screw to achieve a smooth idle.
- Check for Air Leaks: Check for air leaks around the carburetor and intake manifold. Air leaks can cause a lean fuel mixture and rough idling.
- Check the Spark Plug: Make sure the spark plug is clean and properly gapped.
- Engine Lacks Power at High Speeds:
- Adjust the “H” Screw: Fine-tune the “H” screw to achieve maximum power.
- Check the Air Filter: Make sure the air filter is clean. A dirty air filter can restrict airflow and reduce power.
- Check the Exhaust: Make sure the exhaust is not clogged. A clogged exhaust can restrict airflow and reduce power.
- Engine Stalls Frequently:
- Adjust the “L” Screw: Fine-tune the “L” screw to achieve a smooth idle.
- Check the Fuel Supply: Make sure there is fuel in the tank and the fuel filter is clean.
- Check for Air Leaks: Check for air leaks around the carburetor and intake manifold.
- Engine Floods Easily:
- Check the Needle Valve: Make sure the needle valve is sealing properly. A worn or damaged needle valve can cause the carburetor to flood.
- Check the Float: Make sure the float is not sticking or damaged. A sticking float can cause the carburetor to flood.

I’ve found that a systematic approach to troubleshooting is the most effective way to diagnose and resolve carburetor problems. Start with the basics and work your way through the possible causes.

When to Consider a Carburetor Rebuild or Replacement

Sometimes, cleaning and tuning are not enough to resolve carburetor problems. If the carburetor is heavily worn or damaged, you may need to consider a rebuild or replacement. Here are some signs that indicate a rebuild or replacement is necessary:

Worn Throttle Shaft: A worn throttle shaft can cause air leaks and poor performance.
Damaged Carburetor Body: Cracks or other damage to the carburetor body can cause air leaks and fuel leaks.
Heavily Worn Jets: Heavily worn jets can affect the fuel mixture and reduce performance.
Non-Removable Deposits: If you cannot remove deposits from the carburetor passages, a rebuild or replacement may be necessary.

Carburetor Rebuild Kit: A carburetor rebuild kit typically includes new gaskets, diaphragms, needle valve, and jets. Rebuilding the carburetor can restore its performance and extend its life.

Carburetor Replacement: If the carburetor is heavily damaged or worn, a replacement may be the best option. A new carburetor will provide optimal performance and reliability.

My Recommendation: I usually recommend trying a rebuild kit first. It’s a relatively inexpensive way to restore the carburetor’s performance. If the rebuild kit doesn’t solve the problem, then a replacement is the next logical step.

Maintaining Your Stihl BG55 Carburetor for Longevity

Proper maintenance is essential for extending the life of your Stihl BG55 carburetor. Here are some tips for maintaining your carburetor:

Use Fresh Fuel: Always use fresh fuel. Old fuel can break down and leave behind varnish and deposits that clog the carburetor. I recommend using fuel that is no more than 30 days old.
Use Fuel Stabilizer: Add fuel stabilizer to the fuel when storing the blower for extended periods. Fuel stabilizer prevents the fuel from breaking down and forming deposits.
Clean the Air Filter Regularly: A dirty air filter can restrict airflow and cause the engine to run poorly. Clean the air filter regularly with soap and water.
Replace the Fuel Filter Regularly: A clean fuel filter prevents debris from clogging the carburetor. Replace the fuel filter every year or more often if necessary.
Run the Engine Periodically: If you’re not using the blower regularly, run the engine periodically to keep the carburetor from drying out.

I’ve found that a little preventative maintenance goes a long way in preventing carburetor problems. It’s much easier to maintain a carburetor than to repair one.

Safety First: Important Precautions When Working with Carburetors

Working with carburetors involves handling fuel and other potentially hazardous materials. Here are some important safety precautions to follow:

Work in a Well-Ventilated Area: Work in a well-ventilated area to avoid breathing harmful fumes.
Wear Safety Glasses: Always wear safety glasses to protect your eyes from debris and chemicals.
Wear Gloves: Wear gloves to protect your hands from fuel and chemicals.
Avoid Open Flames: Avoid open flames or sparks when working with fuel.
Dispose of Fuel Properly: Dispose of fuel properly according to local regulations.
Disconnect the Spark Plug: Disconnect the spark plug before working on the carburetor to prevent accidental starting.

My Personal Rule: I always make sure to have a fire extinguisher nearby when working with fuel. It’s better to be safe than sorry.

The Importance of Using Quality Fuel and Oil

The quality of the fuel and oil you use can significantly impact the performance and longevity of your Stihl BG55. Here’s why:

Fuel:
- Octane Rating: Use fuel with the octane rating recommended by Stihl. Using fuel with a lower octane rating can cause engine knocking and damage.
- Ethanol Content: Avoid using fuel with high ethanol content. Ethanol can damage the carburetor and other engine components. I recommend using fuel with no more than 10% ethanol.
- Freshness: Use fresh fuel. Old fuel can break down and leave behind varnish and deposits that clog the carburetor.
- Oil:
- Two-Cycle Oil: Use a high-quality two-cycle oil that meets Stihl’s specifications. Using the wrong type of oil can cause engine damage.
- Mixing Ratio: Mix the oil and fuel in the correct ratio. Using too much oil can cause the engine to run poorly, while using too little oil can cause engine damage. The recommended mixing ratio for the Stihl BG55 is typically 50:1.

My Experience: I’ve seen firsthand the damage that can be caused by using poor-quality fuel and oil. It’s worth spending a little extra money on quality products to protect your investment.

Understanding the Role of the Spark Arrestor

The spark arrestor is a small screen that prevents sparks from exiting the exhaust system. This is important for preventing wildfires. Here’s what you need to know about the spark arrestor:

Location: The spark arrestor is typically located in the muffler.
Maintenance: Clean the spark arrestor regularly to ensure proper engine performance. A clogged spark arrestor can restrict airflow and reduce power.
Cleaning: Use a wire brush to clean the spark arrestor. Be careful not to damage the screen.

I always make sure to clean the spark arrestor on my BG55 regularly. It’s a simple task that can make a big difference in the engine’s performance.

Case Study: Reviving a Neglected Stihl BG55

I recently had the opportunity to revive a Stihl BG55 that had been neglected for several years. The blower was covered in dirt and grime, and the engine wouldn’t start. Here’s what I did:

Cleaning: I started by cleaning the blower thoroughly with soap and water.
Carburetor Cleaning: I removed and cleaned the carburetor, paying particular attention to the jets and passages.
Fuel System: I replaced the fuel filter and fuel lines.
Spark Plug: I replaced the spark plug.
Air Filter: I cleaned the air filter.
Tuning: I adjusted the carburetor settings to achieve optimal performance.

After a few hours of work, the BG55 was running like new. The owner was amazed at the transformation. This case study demonstrates the importance of proper maintenance and the potential for reviving neglected equipment.

The Future of Small Engine Technology

As technology advances, small engines are becoming more efficient and environmentally friendly. Here are some trends to watch for:

Electronic Fuel Injection (EFI): EFI systems provide more precise fuel control and reduce emissions.
Battery-Powered Equipment: Battery-powered blowers and other equipment are becoming increasingly popular. They are quieter, cleaner, and easier to maintain than gas-powered equipment.
Improved Engine Designs: Manufacturers are constantly developing new engine designs that are more efficient and durable.

While these advancements are exciting, I believe that gas-powered equipment will remain a viable option for many years to come. The Stihl BG55 is a testament to the durability and reliability of gas-powered equipment.