Honda Rotary Mower Carburettor: A Comprehensive Guide

Understanding Your Honda Rotary Mower's Carburettor

The carburettor is a vital component of your Honda rotary mower, responsible for mixing air and fuel in the correct ratio to power the engine. Over time, this crucial part can become clogged with debris, wear out, or simply require replacement due to age. This guide will walk you through the process of changing the carburettor on your Honda HR173 rotary mower, ensuring your machine continues to perform at its best. We will cover everything from identifying the carburettor to performing the replacement and essential post-maintenance checks.

Component Identification: Locating the Carburettor

Before you begin, it's essential to know where the carburettor is located on your Honda HR173. Referencing the component identification diagram in your owner's manual (page 4), you'll typically find the carburettor situated between the fuel tank and the engine's intake manifold. It's usually a compact unit with fuel lines and linkages connected to it. The air cleaner assembly is often mounted directly to the carburettor, so you'll need to remove that first.

Safety First: Essential Precautions Before You Start

Working on any machinery requires a commitment to safety. Before you even think about touching a wrench, ensure you adhere to the following precautions:

• Disconnect the Spark Plug Cap: This is the most critical safety step to prevent accidental engine starts. Page 22 of your manual explicitly states to disconnect the spark plug cap before performing any maintenance.
• Work in a Well-Ventilated Area: Fuel is flammable. Ensure you are in a well-ventilated space away from open flames or sparks.
• Allow the Engine to Cool: The engine and exhaust components can become very hot. Allow the mower to cool down completely before starting any work.
• Wear Appropriate Safety Gear: This includes sturdy gloves to protect your hands from sharp edges and fuel, and safety glasses to protect your eyes.
• Drain the Fuel: To minimise the risk of spills and fire, it's advisable to drain the fuel from the tank and the carburettor before removal. Refer to page 21 for instructions on draining the fuel tank and carburettor.

Step-by-Step Carburettor Replacement

Here's a detailed breakdown of how to replace the carburettor on your Honda HR173:

1. Remove the Air Cleaner Assembly

The air cleaner assembly is typically attached to the carburettor with a wing nut or screws. Unscrew the wing nut (as shown on page 25) and carefully remove the air cleaner cover and the air cleaner element. Keep these parts clean and set them aside.

2. Disconnect Fuel Lines and Linkages

The carburettor is connected to the fuel tank via a fuel line. You may also find throttle linkages connected. Carefully disconnect the fuel line. It's a good idea to have a small container ready to catch any residual fuel. If there are throttle linkages, gently detach them. Note how these are connected, as you'll need to reattach them correctly later.

3. Remove the Old Carburettor

The carburettor is usually held in place by a couple of bolts or nuts. Locate these fasteners and use the appropriate wrench or socket to remove them. Once the fasteners are removed, gently pull the old carburettor away from the engine. Be mindful of any gaskets or O-rings that might be present between the carburettor and the engine; these should be replaced with new ones.

4. Prepare and Install the New Carburettor

Before installing the new carburettor, ensure it's the correct replacement part for your Honda HR173. Compare it visually with the old one. Attach any necessary new gaskets or O-rings to the new carburettor.

Carefully position the new carburettor onto the engine's intake manifold, ensuring it aligns correctly. Reinstall the bolts or nuts that hold the carburettor in place. Tighten them securely but avoid over-tightening, which could damage the threads or the carburettor body.

5. Reconnect Fuel Lines and Linkages

Reconnect the fuel line to the new carburettor, ensuring a secure fit. Reattach any throttle linkages, making sure they are connected in the same way they were on the old carburettor. Refer to the throttle cable adjustment section on page 28 if you suspect any issues with throttle control.

6. Reinstall the Air Cleaner Assembly

Place the air cleaner element back into its housing, followed by the air cleaner cover. Secure the cover with the wing nut or screws. Ensure the air cleaner is properly seated to prevent dirt from entering the engine.

Post-Replacement Checks and Starting the Engine

Once the new carburettor is installed, it's time to prepare for starting the engine:

1. Check Engine Oil and Fuel Levels

As per page 11, always check your engine oil level and ensure the fuel tank is filled with the correct type of gasoline. Refer to pages 12 and 13 for detailed information on oil and fuel requirements.

2. Prime the Fuel System (If Necessary)

Some carburettors have a primer bulb. If yours does, press it several times to ensure fuel is delivered to the carburettor. Consult your mower's specific manual if unsure.

3. Start the Engine

Follow the starting procedure outlined on page 14. Generally, this involves:

• Turning the fuel valve ON.
• Moving the throttle lever to the START (CHOKE) position.
• Moving the flywheel brake lever forward and holding it against the handlebar.
• Pulling the starter rope briskly.

Once the engine starts, gradually move the throttle lever to the HI position as the engine warms up.

4. Listen for Unusual Noises and Check for Leaks

As the engine runs, listen for any abnormal sounds. Check around the carburettor and fuel lines for any signs of fuel leaks. If you detect any leaks or hear unusual noises, stop the engine immediately and re-check your work.

5. Test Operation and Cutting Height Adjustment

With the engine running smoothly, test the throttle control to ensure it responds correctly. If you notice any issues, you may need to adjust the throttle cable (page 28). Also, check the cutting height adjustment levers (page 17) to ensure they are functioning correctly.

Troubleshooting Common Issues

If your mower doesn't start or runs poorly after changing the carburettor, consult the troubleshooting section on page 32 of your manual. Common issues and their potential solutions include:

Maintenance Schedule and Further Tips

Regular maintenance is key to prolonging the life of your mower and its components. Refer to the maintenance schedule on page 23 for recommended service intervals. Key maintenance tasks related to the carburettor and engine include:

• Air Cleaner: Clean or replace the air cleaner element regularly (page 24). A dirty air cleaner significantly impacts carburettor performance.
• Spark Plug: Inspect and clean or replace the spark plug as recommended (page 26).
• Fuel System: Ensure you use fresh, clean fuel. Avoid using stale or contaminated gasoline. If you use gasohol, ensure it meets Honda's recommendations (page 13).
• High Altitude Operation: If you operate your mower at altitudes above 6,000 feet, consult an authorized Honda dealer for carburetor modifications to improve performance (page 17).

When to Seek Professional Help

While this guide provides comprehensive steps, there may be instances where professional assistance is required. If you encounter persistent problems, are uncomfortable with any part of the process, or suspect a more complex issue, do not hesitate to contact an authorized Honda dealer. They have the specialized tools and expertise to diagnose and resolve any issues effectively. Remember, your satisfaction is important, and Honda dealers are there to help.

By following these steps and safety precautions, you can successfully change the carburettor on your Honda HR173 rotary mower, ensuring it continues to provide reliable service for years to come. Regular maintenance and prompt attention to any performance issues will keep your mower in peak condition.

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