Honda SH300 Owner's Manual page 59

If all keys are lost, the PGM-FI unit/ignition
control module must be replaced. To avoid
this possibility we recommend that if only
one key is left, you immediately have it
reproduced to ensure that a back up is
available.
These keys contain electronic circuits that
are activated by the immobilizer system
(HISS).
They will not work to start the engine if the
circuits are damaged.
• Do not drop the keys or set heavy objects
on them.
• Do not grind, drill or in any way alter the
original shape of the keys.
• Keep the keys away from magnetic
objects.
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