83 Honda Nighthawk, Alternator issues?

I have an 83 650 honda nighthawk. Brand new battery two days ago, dies while im riding. I charge it up and check voltage at idle, steady 12.3 V when revved to 4500 its at about 13.5 V so why is this thing not charging itself????

 

There was a TSB on this wayyyyy back in the 80's when these bikes were new. They all have a habit of not charging if ridden at low revs/stop and go driving. There was an upgrade installed by Honda under warranty back then. Good luck finding any info about it nowadays from any Honda dealer, let alone getting the upgrade for free. You would have to find a really good Honda dealer who has some mechanics who have been around awhile, who also have a good enough memory and a willingness to dig around a bit for part numbers and such. Still, madder things have happened I guess. Other than that, there are the usual crappy connections in the old wiring harness, bad battery, bad regulator/rectifier issues you can attack.

Or, you can just keep the revs up and see what happens. Might be a free fix right there...

Try to find a good Nighthawk site and ask around. The upgrades may be sitting on a shelf somewhere, or at least someone could supply part numbers, or an aftermarket workaround.

 

13.5VDC at 4500 RPMs seems kinda low to me. I know that my dinky Yammie SR250 is supposed to be putting out 14VDC at 2000 RPMs. Don't know anything about the NightHawk 650 specs (but I'm sure there is a forum out there who does). If you have a wiring diagram, does it have a similar 3-winding alternator like the XJs? If so, you can check each winding for proper voltage like the XJs. [I believe this bike has a reg/rec like many Jap bikes - dumps excess current in the form of heat, unlike the XJs that have a field winding in the alternator like autos.] If the alternator is putting out correct voltage then try a good reg/rec.

 

You could try this site for help
http://nighthawk-forums.com/

They are a friendly bunch and are willing to help as mush as the folks around here.