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Hey, problem is with my friends bike. Its a yamaha xs650 twin. The charging system isnt working or it wont charge. It will run good only if it is being kept alive on a battery charger. Battery IS good and WILL hold a charge. Just wondering if you guys could point me in the right direction and list a few suggestions on what to try. Where should I use a multimeter, stator, ??? any help would be greatly appreciated.

come on. I know its not a kawi, but im sure plenty of you would be able to point me in the right direction.

If you are getting no charge at all, it could be the rectifier assembly. Get a manual for the bike and follow the procedure for Ohming out each rectifier in the rectifier bridge. Those often blow out. In some bikes the rectifier and regulator are in the same module.

It could be the alternator (rotor + stator assembly). I don't know what the open circuit voltage it should put out when it spins, the manual would tell how to check it.