Honda FG400 Owner's Manual page 30

SERVICING YOUR HONDA TILLER
Never use stale or contaminated gasoline or an oil/gasoline mixture. Avoid
getting dirt or water in the fuel tank.
Occasionally you may hear light "spark knock' or "pinging" (metallic rapping
noise) while operating under heavy loads. This is no cause for concern.
If spark knock or pinging occurs at a steady engine speed, under normal load,
change brands of gasoline. If spark knock or pinging persists, see an
authorized Honda servicing dealer.
I
NOTICE
I
Running the engine with persistent spark knock or pinging can cause e
damage.
Running the engine with persistent spark knock or pinging is misuse, and the
Distributor's Limited Warranty does not cover parts damaged by misuse.
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