Why are my petrol-powered grass trimmer and brushcutter smoking excessively?
If your Husqvarna petrol-powered grass trimmer or brushcutter is producing more smoke than usual, it’s often caused by an incorrect fuel mixture, restricted airflow or engine overheating.
Light grey smoke from the exhaust can occur occasionally, but excessive or persistent smoke should be investigated before continuing to use the machine.
Quick check
Before troubleshooting, ask yourself:
- Is the smoke coming from the exhaust?
- Did you recently mix fresh fuel?
- Has the air filter been cleaned recently?
- Is the engine unusually hot?
These checks help identify the most common causes quickly.
Most common causes and fixes
Incorrect fuel mixture
Too much two-stroke oil in the fuel mixture is the most common cause of excessive smoke.
What to do:
- Empty the fuel tank if necessary
- Refill using fresh fuel mixed to the correct ratio
Always follow the recommended fuel mixture for your product.
Related guide:
How to mix two-stroke oil and fuel
Old or stale fuel
Fuel that has been stored for a long period does not burn efficiently and may increase exhaust smoke.
What to do:
- Replace old fuel with a fresh fuel mixture
Dirty air filter
A restricted air filter reduces airflow, causing the engine to run with a richer fuel mixture and produce more smoke.
What to do:
A restricted air filter reduces airflow, causing the engine to run with a richer fuel mixture and produce more smoke.
What to do:
- Remove the air filter
- Clean or replace if necessary
A clean air filter improves combustion and engine performance.
Related guide:
How to clean or replace the air filter
Engine overheating
An overheating engine may begin smoking, especially after prolonged use or when airflow is restricted.
What to do:
- Stop using the machine
- Allow it to cool completely
- Check that the cooling system is clean and free from debris
Related guide:
Restricted spark arrestor
A blocked spark arrestor can restrict exhaust flow, causing poor engine performance, reduced RPM and excessive heat.
Husqvarna recommends cleaning the spark arrestor approximately every 50 hours of operation on models equipped with one.
What to do:
- Inspect the spark arrestor
- Remove carbon deposits using a wire brush
- Replace it if damaged
Related guide:
What does a spark arrestor do?
When should you stop using the machine?
Stop using the grass trimmer or brushcutter if:
- Smoke becomes heavier during operation
- You smell burning
- Smoke comes from somewhere other than the exhaust
- Engine power drops significantly
Continuing to operate the machine may result in further engine damage.
Prevent excessive smoking
To help prevent smoking:
- Use fresh, correctly mixed fuel
- Clean the air filter regularly
- Inspect the spark arrestor
- Keep the cooling system clean
- Follow the recommended maintenance schedule