1991 Honda Night Hawk 750.., battery fine but the fuse box clicks when I push the start button, nothing else happens.

There are no moving parts in your fuse box. The clicking sound is the contact bar closing in your starter solenoid.Follow your positive battery cable to your starter solenoid. If your push your starter button and you hear a click in the starter solenoid , then your starter button is good. If you take a piece of wire, a screw driver, or simply touch the the two power cables on the the starter solenoid together you will be putting power directly to your starter. If you jump the solenoid and the starter works you need to replace the starter solenoid. If with direct power to the starter, you tap the starter with a plastic hammer and the starter works, you need new starter brushes. Anything else wrong with the starter and you will need to replace the starter assembly the manufacturers do not sell replacement parts for there starters (only the brushes).