Honda GC135 Owner's Manual page 38

HELPFUL TIPS &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.