Try this link.
http://www.mediafire.com/?mlgyt355ynv Looks like the geniune Honda manual to me. I did a Google search for 1992 Honda Nighthawk factory service manual.
Good luck, I hope this helps, and keep us informed on your progress.
Luke M
Used to have a 1979 CB750L, sold it as a parts bike, now riding a slightly modified 1984 VT700C. Network/Field Engineer. Central OH, USA, Earth, Sol System, Milky Way Galaxy, Universe.