Motorcycle Repair: Yamaha Dragstar Battery not charging, stator coils, xvs650 dragstar

Question
Hi Chris, I hav a 1997 XVS650 Dragstar and my battery ran flat while i was out on my bike. I first tried charging the battery wich worked fine for a day or two until it ran flat again. I then bought a new battery but after some time it too ran flat as well. I borrowed a rectifier from a friend who has the same make and model of bike (same year as well) and took a reading from the battery terminals, when the engine was turned off it read something like 12.40 volts and when the engine was running it was the same (even slightly less 12.38v )this is the same reading i got with my own rectifier connected. The strange thing was when i took a reading from my friends bike i got the same reading 12.40v slightly less with engine running, but his bike seems to work fine, though he does not have it out much. (unless he has the same prob and his battery hasn't run down yet) I also checked the coil on the altinator for breaks but nothing looked wrong there. This problem really has me baffeled so any help you can give me would be much appreciated. (please excuse any bad spellings!)

Answer
Hi Andre.
 Regulator/rectifiers almost never go bad.

 What you have is a problem with the stator coil.  It could be a bad coil or a bad connection.  My money, based on what you have told me, is on the stator failing.

Replace it.

 Stator coils usually go bad about every 3-5 years or 40,000 to 50,000 miles.  It seems to be more frequent on the newer bikes for some reason.

 They should be putting out no less than 13 VDC at the terminals when the bike is running.

Good luck.
FALCON