Ducati Superbike 749R 2006 User And Maintenance Manual page 129

Tank filler plug (fig. 29)
Opening
Lift the protective cap (1) and insert the key into the lock.
Give the key a 1/4 turn clockwise to unlock.
Lift the plug.
E
Closing
Close the plug with the key inserted and push it into
the seat. Turn the key anticlockwise to the initial position
and take it out. Close the protective cap (1).
Notes
The plug can only be closed with the key inserted.
Warning
After each refuelling (see page 53) always make sure
that the plug is correctly replaced and locked.
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https://www.motorcycle-manual.com/
1
fig. 29