My Petrol Chainsaw will not idle

Overview

This article explains the checks you can carry out if your chainsaw stalls when the throttle trigger is released or is unable to maintain a stable idle speed.

Step-by-Step Guide

Step 1: Safety First

• Operate the chainsaw only in a safe, well-ventilated area
• Ensure the chain brake is engaged when carrying out checks
• Keep hands clear of the chain during any running adjustments

Possible Causes & Basic Checks

Check the Fuel

• Ensure fuel is fresh (less than 30 days old)
• Confirm correct fuel-to-oil ratio (e.g. 40:1 where applicable)
• Old or incorrect fuel can cause poor idling and stalling

Check the Air Filter

• Remove and inspect the air filter
• Clean or replace if dirty or blocked
• A restricted filter reduces airflow and affects idle stability

Check the Fuel Cap

• Ensure the fuel cap is correctly fitted
• Tighten by hand until secure
• Do not overtighten, as this may restrict fuel flow

Carburettor Adjustment

⚠️ Only attempt this if you have mechanical experience and the correct adjustment tool.

Incorrect adjustment may cause serious engine performance issues.

Tools Required

• Carburettor adjustment tool

Procedure

• Start the chainsaw and allow it to warm up fully
• Locate the carburettor adjustment screws:
  • L = Low speed adjustment
  • H = High speed adjustment

Adjusting Idle (L Screw)

• Turn the L screw until the engine idles smoothly
• Ensure the chain does not rotate at idle
• Fine-tune until stable idle is achieved

Adjusting High Speed (H Screw)

• Run the chainsaw at full throttle
• Turn the H screw anti-clockwise until the engine begins to struggle
• Slowly turn clockwise until the engine returns to smooth full speed operation

If You Are Unable to Complete This Procedure

If you are not confident adjusting the carburettor:

• Stop making adjustments immediately
• Contact our Technical Support Team

A replacement carburettor or professional servicing may be required. Warranty support may apply if the product is within its coverage period.

Frequently Asked Questions

Why does my chainsaw cut out when I release the throttle?

This is usually caused by incorrect idle settings, blocked air filter, or stale fuel.

Can fuel cause idle problems?

Yes. Old fuel or incorrect mixing ratios can prevent stable idling.

Is it safe to adjust the carburettor myself?

Only if you have the correct tool and experience. Incorrect adjustment can damage the engine.

What is the most common cause of poor idle?

A dirty air filter or incorrect L-screw setting is the most common cause.

Do I need to warm the engine before adjusting idle?

Yes. Always allow the engine to warm up fully before making adjustments.