Honda Motorcycle Owner's Manual page 39

Your engine is designed to use any gasoline
that has a pump octane number of 86 or higher.
Gasoline pumps at service stations normally
display the pump octane number.
We recommend that you use unleaded fuel
because it produces fewer engine and spark
plug deposits and extends the life of exhaust
system components.
Never use stale or contaminated gasoline or an
oil/gasoline mixture. Avoid getting dirt, dust or
water in the fuel tank. Use of a lower octane
gasoline can cause persistent "pinging" or
heavy "spark knock" (a metallic rapping
noise) which, if severe, can lead to engine
damage.
31
NOTICE
If "spark knock" or "pinging" occurs at a
steady engine speed under normal load, change
brands of gasoline. If spark knock or pinging
persists, consult your authorized Honda dealer.
Failure to do so is considered misuse, and
damage caused by misuse is not covered by
Honda' s Limited Warranty.
Occasionally you may experience light spark
knock while operating under heavy loads. This
is no cause for concern, it simply means your
engine is operating efficiently.