Mower is smoking black smoke

Symptoms

• Smoke is dark black or sooty
• Engine may run rough or lack power
• Strong gasoline smell in the exhaust
• Spark plug may appear black and sooty when checked

Likely causes

• CommonClogged or dirty air filterRestricted air makes the fuel mixture too rich, producing black smoke.
• CommonChoke stuck closedA choke that doesn't fully open keeps the engine running rich after warm-up.
• PossibleCarburetor float or needle issueA stuck float lets too much fuel into the carburetor bowl.
• PossibleWrong fuel mixture (2-stroke engines)Too much oil in a 2-stroke fuel mix causes excess smoke.

What to do

1. Check and clean or replace the air filter if it's dark, clogged, or torn.
2. Confirm the choke fully opens once the engine warms up and isn't sticking closed.
3. Let the engine run at idle and watch whether smoke lessens once warm; persistent smoke suggests a carburetor issue.
4. For 2-stroke equipment, verify the fuel was mixed at the correct oil-to-gas ratio in the manual.
5. If smoke continues with a clean filter and working choke, the carburetor likely needs cleaning or adjustment.
6. Turn off the engine and let it cool if it's been smoking heavily before doing further work.

Tools and parts

• Replacement air filter

When to call a pro

If the air filter and choke are fine but black smoke continues, a small engine mechanic should inspect and adjust the carburetor.

Safety