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Last updated October 28, 2026 · Applies to: lawn mowers from Toro, Husqvarna, Honda, Troy-Bilt, John Deere and Craftsman and others
Step 1: Recognize the symptoms of bad gas
Step-by-step instructions for this step are being written.
Fuel path: tank to cylinder. Fuel must flow through every stage. A blockage at any box starves the engine.
Step 2: Check the fuel for water and varnish
Step-by-step instructions for this step are being written.
Fuel path: tank to cylinder. Fuel must flow through every stage. A blockage at any box starves the engine.
Step 3: Drain the tank and carburetor bowl
Step-by-step instructions for this step are being written.
Inside a float-bowl carburetor. Varnish from old fuel usually blocks the main jet or emulsion tube first.
Step 4: Clean or replace the carburetor
Step-by-step instructions for this step are being written.
Inside a float-bowl carburetor. Varnish from old fuel usually blocks the main jet or emulsion tube first.
Step 5: Refill with fresh, stabilized fuel
Step-by-step instructions for this step are being written.
Fuel path: tank to cylinder. Fuel must flow through every stage. A blockage at any box starves the engine.
Brand notes
Brand-specific notes for Toro, Husqvarna, Honda and Troy-Bilt are being researched.
When to take it to a shop
Hand it over if the engine still will not run after the fuel, spark and air checks, if you find metal in the oil or the
engine is seized, or if the machine is under warranty (opening it yourself can void it).
Find a lawn mower repair shop near you
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Answers being written: How long does gas last in a lawn mower? · Can bad gas ruin an engine? · Does ethanol gas hurt small engines? · What do I do with old gas?