Honda HRX217TDA Owner's Manual page 52

STORAGE
Fuel
Gasoline will oxidize and deteriorate in storage. Old gasoline will cause
hard starting, and it leaves gum deposits that clog the fuel system. If
the gasoline in your mower deteriorates during storage, you may need
to have the carburetor and other fuel system components serviced or
replaced.
The length of time that gasoline can be left in your fuel tank and
carburetor without causing functional problems will vary with such
factors as gasoline blend, your storage temperatures, and whether the
fuel tank is partially or completely filled. The air in a partially filled fuel
tank promotes fuel deterioration. Very warm storage temperatures
accelerate fuel deterioration. Fuel deterioration problems may occur
within a few months, or even less if the gasoline was not fresh when
you filled the fuel tank.
The Distributor's Limited Warranty (page 70) does not cover fuel
system damage or engine performance problems resulting from
neglected storage preparation.
You can extend fuel storage life by adding a gasoline stabilizer that is
formulated for that purpose, or you can avoid fuel deterioration
problems by draining all the fuel from the fuel tank and carburetor.
Adding a Fuel Stabilizer
When adding a fuel stabilizer (page 64), 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 the treated gasoline has replaced the
untreated gasoline in the carburetor.
3. Turn the engine OFF and turn the fuel valve to the OFF position
(page 23).
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