1983 XS650

[reaver536]

I have an 83 xs650 with a specific problem. when I take the fuse out for the headlight, the bike runs fine. I am able to kick start it in 1 try and while riding it seems to be perfect. I am unable to eclectic start the bike because it sounds like it isn't getting enough juice. When I plug the fuse for the headlight in the headlight works and I can still kick start the bike. I am not able to electric start the bike as well. but When I pull on the throttle to give it gas he begins to sputter like there isn't enough of juice. I've left my battery on a charger low voltage over night and I have used a friends battery from his xs650 which seems to be working for him but yet I still have the same issue. Both batteries seem to be fine yet I still get the sputter. Ive completely replaced the alternator and when I'm idling i hover around 12.5, when I rev it up I go all the way up to 14 / 14.5. Ive also put the headlight fuse back in and unplugged the headlight itself and ran it directly off the frame to see if it was a short in the wire but that didn't seem to be the issue... I checked my plugs which are new and they work fine.. I have new Brushes in the alternator. I'm sure there are a few things I'm missing which i tested but I can't seem to remember. all i know is that whenever i have the headlight connected and running the bike runs poorly, it sputters and acts as if it isn't getting enough juice. when the headlight isn't attached it runs fine, yet it still wont start with the starter I have to kick start it.
any ideas??