I also have an 83 nighthawk 650. I had a problem with my charging system also. It would help if you told us what it was doing? I changed out my rectifier and also my stater and my system is charging properly. Without knowing what is going on with your bike I can not tell you where to start.
firing order 1984 650 nighthawk
0.8-0.9mm
GN-4 10w-40 Honda motor
what's the firing order in a nh 550 cc 1983
Bad needle and seat Throttle cable misadjusted
under the head light right behind the horns (front of the bike)
Front left fork, right below turn signal. Should see model and Vin
left 15.7 right 15.2, 0-10 psi
If everything is functioning properly, nothing is missing and the cosmetics are decent, then the bike should be worth around $1,100.
Have the charging system checked. The light comes on when there is a charging system problem. it may be a battery, alternator or a battery problem.
The rear can be lowered by different height shocks. The front can have shorter forks installed or have the frame cut and the angle changed, lengthening the bike as well as lowering it.
your voltage regulator maybe the problem\ i had same problem with my 82 750 nighthawk . check voltage at connection, see you service manuel for instruction. hope that helps