Honda VFR800A 2005 Owner's Manual page 110

Fuel
Use of lower octane gasoline can cause
persistent ''pinging'' or ''spark knock'' (a
loud rapping noise) which, if severe, can
lead to engine damage. Light pinging
experienced while operating under a heavy
load, such as climbing a hill, is no cause
for concern.
If pinging or spark knock occurs at a
steady engine speed under normal load,
change brands of gasoline. If pinging or
spark knock persists, consult your Honda
dealer.
101
Servicing Your Honda