My Petrol Lawnmower Is Leaking Fuel from the Primer Bulb 

If fuel is leaking from the primer bulb on your lawnmower, this is usually caused by fuel backing up from the carburettor and escaping through the primer system.

Table of Contents

1. What Causes Primer Bulb Fuel Leaks?
2. The “Bleed & Tap” Procedure
3. Restarting the Machine
4. If the Problem Persists

What Causes Primer Bulb Fuel Leaks?

If fuel is coming out of the primer bulb, it typically indicates that:

• Fuel is overfilling the carburettor float chamber
• The float valve inside the carburettor is stuck open
• Fuel is being forced back through the primer line

In most cases, the issue is caused by a temporarily stuck float valve, which can often be resolved without replacing parts.

The “Bleed & Tap” Procedure

This simple procedure helps release pressure from the carburettor and free a stuck float valve.

Step 1 – Locate the Carburettor

Find the carburettor on the engine.

It is a metal component approximately the size of a fist, located between the air filter and the engine block.

Step 2 – Loosen the Float Chamber Nut

You will see two main nuts on the carburettor:

• One at the bottom
• One positioned at an angle (approximately 45°)

Using a suitable spanner, carefully loosen the angled nut.

Important: Do not fully remove the nut.

Step 3 – Bleed Excess Fuel

Allow fuel to drain from the loosened nut for approximately 20–30 seconds.

This relieves pressure and clears excess fuel from the carburettor chamber.

Step 4 – Re-Tighten the Nut

Once fuel has stopped draining:

• Retighten the angled nut securely
• Ensure it is properly sealed, but do not overtighten

Step 5 – Tap the Carburettor Float Chamber

Using a spanner, screwdriver handle, or similar tool:

• Gently tap the float chamber area of the carburettor a few times

This helps free the internal float valve if it is sticking.

Restarting the Machine

Once the procedure is complete:

1. Attempt to start the lawnmower as normal.
2. Prime the engine if required.
3. Check for any further fuel leakage from the primer bulb.

This guide explains how to remove and replace the exhaust assembly on an SE475 engine.

Table of Contents

1. Tools Required
2. Removing the Exhaust
3. Replacing the Exhaust
4. Reassembling Components
5. Final Checks

Tools Required

• 10mm spanner or socket wrench

Removing the Exhaust

Step 1 – Remove Retaining Nuts

Locate the exhaust retention nuts.

• Undo the 2 x 10mm exhaust retention nuts
• These are typically positioned on the exhaust mounting points (see reference image markings)
• 

Step 2 – Remove the Exhaust Cover

Once the nuts are removed:

• Carefully take off the exhaust cover
• Place it safely to one side

Ensure no parts are damaged or dropped during removal.

Step 3 – Remove the Exhaust Assembly

With the cover removed:

• Carefully detach the exhaust assembly from the engine
• Set the exhaust assembly aside safely

Replacing the Exhaust

Step 4 – Fit the New Exhaust Assembly

Before installation:

• Check that the exhaust heat gasket is correctly positioned and undamaged

Then:

• Fit the new exhaust assembly into position on the engine
• Ensure it sits correctly and aligns with the mounting points

Step 5 – Refit the Exhaust Cover

• Place the exhaust cover back into its original position
• Ensure it aligns correctly with the mounting holes

Step 6 – Secure the Assembly

• Reinstall the 2 x 10mm nuts
• Tighten securely to ensure all components are firmly held in place

Do not overtighten, but ensure there is no movement in the assembly.

Final Checks

After installation:

• Confirm the exhaust is firmly secured
• Check that the gasket is seated correctly
• Ensure there are no loose parts or gaps
• Start the engine briefly to confirm normal operation