Honda GX610 Owner's Manual page 41

HELPFUL TIPS 81 SUGGESTIONS
The Distributor's Limited Warranty does not cover fuel system damage or
engine performance problems resulting from neglected storage preparation.
You can extend fuel storage life by adding a fuel stabilizer that is formulated
for that purpose, or you can avoid fuel deterioration problems by draining the
fuel tank and carburetor.
ADDING A FUEL STABILIZER TO EXTEND FUEL STORAGE LIFE
When adding a fuel stabilizer, fill the fuel tank with fresh gasoline. If only
partially filled, air in the tank will promote fuel deterioration during storage. If
you keep a container of gasoline for refueling, be sure that it contains only fresh
gasoline.
1. Add fuel stabilizer following the manufacturer's instructions.
2. After adding a fuel stabilizer, run the engine outdoors for 10 minutes to be
sure that treated gasoline has replaced the untreated gasoline in the
carburetor.
3. Stop the engine, and if the fuel tank is equipped with a fuel valve, move the
fuel valve to the CLOSED or OFF position.
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