The best I could find for you was here:
http://www.hondanighthawks.net/79cb650wdgr.pdf
located on this page
http://hondanighthawks.net/repair.htm
but really, you should pick up a service manual for that bike, so you at least have the basics, like torque specs and fluid levels. Check your grounds, they're the first to go.
... upon further investigation, it seems like the nighthawk does have wiring problems. Since your brakelight is having problems, it might be in the throttle control assembly (starter switch)