XS400 Member
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Manitoba canada
Hello this is my first post so I hope I'm doing it correctly...
I'm having an issue with my charging system I've read the forums but I belive it my be incorrect info for my bike(79 xs400f).
The issue I'm having was an over charging issue now that I've replaced my stock regulator with a vr115/vr292 which everything I've read says is correct. But now I'm not getting any charge.
So is this just wrong information and need a vr125 instead or am I missing something? Thanks in advance.
Ok I've found a thread that says my bike requires the other vr125 style regulator. Ive tried the vr125 But still getting an over charge. I've also tested the wiring and found the stator wires were shot so i fixed them but im getting a voltage drop of about 2 volts at both green and brown field coil wires and not sure why. Now I get over charging with either regulator(may have toasted the vr115)?. Anyone got any ideas?
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Hmmm every time i go and look at the styles of voltage regulators i get ones for a car/truck.I am sure they wont work if that is what you are using.
What voltage are you measuring when it is over charging?
Thanks for replying! Yes all the regulators are for cars/trucks and many people on here have good luck with them. I am getting over 15 volts but I just did a test jumping the red permanent 12v to the brown switch 12v wire and got proper charging voltage(14.2-14.3) with the stock regulator finally! I now have to figure out why the brown wire is giving incorrect voltage/input. Will update when I figure it out!
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I also went through the VR dance when I first got my 1978. But after almost a year, voltages are still working great. I detailed it in this thread: Re-Ring, Dodge VR and Starter Clutch Springs | Yamaha XS400 Forum. Also, if you are getting 2 volts of drop, that will definitely mess with regulation as it is a comparator between battery volts and alternator output. One of the things I did on mine was to un-plug and re-plug every single connector in the harness a few times to knock off any corrosion from sitting a few years. Pull the tank, side covers and headlight to get them all. Maybe you just have some crud on the connectors causing the voltage drop.
Thanks! I'm having a tuff time finding the cause of the voltage drop. Do you think I can just use a jumper/ wire the brown signal wire straight to the battery? Or is that a big nono?
Personally I wouldn't. I would rather unwrap the entire harness and find the bad part and if i couldn't see anything wrong i would remove the old wire and replace the wire then wrap the harness back up.
Not saying that it is a big no no or what I would do is the rite way, it is just what I would do.
But for testing purposes I would use a jumper wire......but I would put a fuse in that jumper Just in case something goes terribly wrong.
remember Murphy is always out there.

Just a thought.... I am almost positive that the 20 amp fuse is in between the battery and the regulator. If it is change the fuse.It is extremely rare but I have seen a fuse once or twice develop a resistance. It is a long shot but worth it to eliminate the possibility.
I should mention I also carefully sanded all the fuse holder contacts with some fine sand paper wrapped around a large diameter nail to remove corrosion there as well. I hit the fuse ends as well but I do plan on replacing my fuse box with a more modern ATC style eventually.
Ok I have finally figured it out! I had all of my rear lights and regulator grounds plugged into the same main ground wire and it was my brake light causing the problem. That or just to many plugged into the same ground wire?
Anyway thanks everyone for your advice and helping me with my problem!