My Petrol Strimmer/Brush Cutter will not rev up

This article covers the basic checks and adjustments that can be performed if your petrol strimmer or brush cutter starts but will not reach higher engine speeds, bogs down under throttle, or cuts out before reaching full revs.

Contents

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

Preliminary Checks

If the engine is not revving up properly and cuts out before reaching higher RPM, please carry out the following checks before adjusting the carburettor:

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 hesitation under throttle.

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 reaching full speed.

Fuel Cap

Ensure the fuel cap is fitted securely and is hand-tight. A loose fuel cap may affect fuel delivery, while an overtightened cap can sometimes restrict tank ventilation.

Carburettor

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

Carburettor Adjustment – H Screw Focus

It is possible that the carburettor settings require adjustment to restore proper engine performance at higher RPM.

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. Check the low-speed setting first by adjusting 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. Slowly turn the H screw anti-clockwise until the engine begins to struggle to reach maximum RPM.
6. Gradually turn the screw clockwise until the engine returns to maximum RPM and runs smoothly.
7. Once the engine accelerates cleanly and reaches full speed without hesitation, the adjustment is complete.

Unable to Perform This Procedure?

If you are unable or uncomfortable carrying out this procedure, you have the following options:

• Order a replacement carburettor.
• Contact our support team for further guidance.
• If your machine is still within its warranty period, arrange for collection and repair by our workshop technicians.

Please note that carburettor adjustments should only be carried out using the correct tools and with appropriate mechanical knowledge, as incorrect settings can lead to further performance issues.