My Petrol Strimmer/Brush Cutter will not idle

This article covers the basic checks and adjustments that can be performed if your petrol strimmer or brush cutter starts but cuts out when the throttle trigger is released.

Contents

• Preliminary Checks
• Carburettor Adjustment – L Screw Focus
• Unable to Perform This Procedure?

Preliminary Checks

If the engine is not running at idle speed and cuts out when you release the throttle trigger, please carry out the following checks:

Fuel

Ensure the fuel is fresh and mixed correctly according to the manufacturer's recommendations. Old or incorrectly mixed fuel can cause poor engine performance and affect idling.

Air Filter

Check that the air filter is clean and free from dirt or debris. A blocked air filter can restrict airflow and prevent the engine from idling correctly.

Fuel Cap

Ensure the fuel cap is fitted securely and is hand-tight. Avoid overtightening or leaving it too loose, as this may affect fuel tank ventilation.

Carburettor

If the above checks do not resolve the issue, the carburettor settings may require adjustment.

Carburettor Adjustment – L Screw Focus

It is possible that the carburettor settings require adjustment to restore a stable idle speed.

Important: This procedure requires a good level of mechanical knowledge. Incorrect adjustment may worsen engine performance or cause starting and running issues. If you are unsure, please contact our support team for assistance.

Tools Required

• Carburettor adjustment ("Pacman") tool

Adjustment Procedure

1. Start the machine and allow it to warm up fully.
2. Locate the two adjustment screws on the carburettor:
   • L = Low-speed adjustment
   • H = High-speed adjustment
3. Slowly adjust the L screw until the engine idles smoothly without stalling and without the cutting head rotating.
4. To adjust the H screw, run the machine at full throttle.
5. Turn the H screw anti-clockwise until the engine begins to struggle to reach maximum RPM.
6. Slowly turn the screw clockwise until the engine returns to maximum RPM and runs smoothly.
7. Once the engine accelerates cleanly and idles correctly, the adjustment is complete.