My Petrol Chainsaw will not rev up

Overview

If your petrol chainsaw starts but does not reach full speed when the throttle is applied, this is usually caused by fuel issues, restricted airflow, or incorrect carburettor settings. In most cases, the problem can be resolved with a few basic checks before any repairs are required.

This guide explains the most common causes and how to safely troubleshoot the issue.

Step-by-Step Guide

Step 1: Check the Fuel

Ensure you are using fresh fuel that is less than 30 days old.

Check the fuel mixture ratio is correct:

• 40:1 fuel-to-oil mix
• 1000ml unleaded petrol
• 25ml 2-stroke engine oil

If the fuel is old or incorrectly mixed, drain and refill the tank with a fresh mixture.

Step 2: Check the Air Filter

Remove and inspect the air filter.

Look for:

• Dirt or debris
• Blockages
• Heavy oil saturation

Clean or replace the air filter if required. A blocked filter will restrict airflow and reduce engine power.

Step 3: Check the Fuel Cap

Ensure the fuel cap is fitted correctly and securely tightened by hand.

A loose or faulty cap can affect fuel delivery and engine performance.

Step 4: Check the Chain Brake

Ensure the chain brake is fully disengaged before use.

If the chain brake is engaged, the engine may run but the chain and throttle response will not operate correctly.

Step 5: Check Carburettor Settings (If Required)

⚠️ Important: Only carry out this step if you are confident with mechanical adjustments. Incorrect settings may damage the engine.

If all other checks are correct, the carburettor may need adjustment.

L Screw (Low Speed):

• Adjust until the engine idles smoothly without chain movement

H Screw (High Speed):

• Run the chainsaw at full throttle
• Turn anti-clockwise until engine struggles
• Slowly turn clockwise until full power is restored

If unsure, contact technical support before adjusting.

If the Issue Persists

If the chainsaw still will not rev up after completing the above checks, the issue may be internal (carburettor fault, fuel system blockage, or air leak).

Please contact our Technical Support Team for further assistance.

Summary

• Use fresh, correctly mixed fuel (40:1)
• Clean or replace the air filter
• Ensure fuel cap is secure
• Confirm chain brake is disengaged
• Check carburettor settings if required

FAQ

Why does my chainsaw start but not rev properly?
This is usually caused by restricted airflow, old fuel, or carburettor imbalance.

Can old fuel cause this issue?
Yes. Fuel older than 30 days can degrade and affect engine performance.

Do I need to adjust the carburettor?
Only if all basic checks fail. Most issues are resolved without adjustment.

Can a blocked air filter affect revving?
Yes. A blocked filter will limit airflow and reduce engine speed and power.

When should I contact support?
If the issue continues after checking fuel, air filter, fuel cap, and chain brake.