1977 regulator question

[FarmBoy72]

I have a 77 xs400 that I recently picked up and it has the old resistor regulator. It doesn't seem to be working very well and I was wondering if I can interchange it with a regulator off of a 1980 xs400?

The regulators both have the same wire colors, just different connectors.

wires on bike harness

Picture of two regulators (top 77, bottom 80)

Wires on regulator connectors (left is 77, right is 80)



EDIT: just went through and checked all of the regulators/rectifiers that I have for the bike, they are all pretty much shot. So has anybody tried updating to a newer combined regulator/rectifier??

 

[XS400Cup]

I can't explain in english, but the pictures may be helpful.

 

[FarmBoy72]

That's what I needed, - Thanks!

 

[FarmBoy72]

Well after replacing my bad regulator I was still having issues. I would get no charge or a slight charge. So I went and checked my stator wires and they were all fine, it was even making 50v AC at 3-4000 rpm. but when plugged in it was being grounded out. I checked my rectifier and all the diodes were good so I decided to try disconnecting the yellow wire that goes to the stator, problem fixed. The bike now charges at a good 14 volts.

Im still just wondering what exactly the yellow wire is for? I know that before I disconnected it the headlamp would turn on by itself when the system was charging

 

[salisride]

kinda late but the yellow wire is for the headlight relay. which keeps the HL off until the bike starts producing power on its own thru the stator. the headlight draws a lot of power so its just there to make it easier to start the bike on battery juice