Electrical troubleshooting need help

[Rob89]

Hi guys new to the forums here. Just got what I believe is a 84 xs400 and am having issues with the charging system. Looking for advice on where to start and how to go through to figure out which component is not working. So far I have ohm'd out the stator and all three coils are identical which leads me to believe it isn't shorted or the cause of the problem but when I start the bike the voltage drops from 12.6v to 12v which tells me it's just running off battery power correct?

Not sure what I should try to test next

 

[16VGTIDave]

Check all the fuses and their holders. Common issue is broken holders in the fuse box.
Next would be corroded connections, or worse yet burned connections. I'd start at the voltage regulator connection.

Let us know what you find!

 

[Rob89]

So went through it last night all connections seems good and no blown fuses. Other part that I failed to mention in original post is bike has been stripped down and modified quite a bit so all that's left electrical wise is ignition signals/lights and battery charging components

 

[BBS360]

Checked the field coil resistance?
Must be a double overhead cam bike? Do their rotors use brushes? Might need to check wear levels on them.

Does the voltage go above 12V if you rev up to around 5000?

 

[Rob89]

Have not checked field cool resistance yet. But voltage is constant 12v when running regardless of rpm which leads me to believe it is just running off battery