Stator / RegRec Wiring Question

[Elder]

Gents, be gentle with me here...
I'm not a mechanic and this is my first bike. That said, I'm also not a total dummy. I have the manual(s) and have some experience with working on small engines. But if I call the magneto the stator or call the stator the alternator... I'm sorry in advance. This part is all new to me.

So here's the rub. I've got, to the best of my knowledge, an '81 xs400H Special II that does not charge. I've replaced the battery with a Lithium, chopped the tail off to build a single-seat, and gotten the ol' girl running on just battery to power the sparks and lights, replaced all the lighting with new LEDs, and rebuilt the entire wiring harness from the ground up. Everything works fine with one exception... The battery (even the original one) has NEVER charged properly. Finally got around to that part of the rebuild and am realizing that I have no idea what I'm doing.

I have about 4 "wrong" reg-recs sitting on my bench. I'm pretty sure I have one that will work now, but there's no wiring diagram for it and the site documentation is pretty vague. I think I've identified the main issue with the original charging system (goober before me pinched off/crushed all the wires between the block and the component that houses the stator). I assume the three white wires from the magneto are just matched up with the other white ones on the RR. Then I lose confidence in my guesses. The RR also has red, black, gray, and green wires. I can GUESS that the red and black run to the battery, but I'm not sure. The gray and green wires apparently go to "switched ground from alternator field" and "voltage sensing input from ignition switch", but I don't know where those are. The magneto also has two additional wires (other than the white "outbound" wires) that I'm unsure of their use. The sheathing on these two is too oil-stained to identify colors on them, but according to the book's wiring diagram, once upon a time they were black and green.

Can any of y'all bike-geniuses help a newbie out and with getting the right wires run to the right places?

I can provide images later if that would help.

Thanks, folks.

 

[CaptChrome]

I will give it a shot. I don't know if the newest reg/rec will work (not a lot of specs and info is given for it), but I can probably help with how to hook it up to try it out. Not having the factory wiring harness might make this more complicated as we could go by exact wire colors if the old harness was used

Anyway, what you should have and will need is five wires coming from the stator/alternator/generator/thingamabob that exit at the bottom of the left-hand engine side cover. You indicate that they are cut, so you are most likely going to have to remove the side cover and solder on some new wires. But what you should find there are five wires - 3 white, a green and a black. The easy part is that the three white wires from the engine need to be connected to the three white wires on the reg/rec. The green wire from the engine is from the field coil in the alternator and is switched to ground by the regulator in the stock bike. So, hook the green wire to the green wire of the new reg/rec. Simple so far, right? The black wire on the bike that remains is positive voltage supply to the alternator field coil. It does not get hooked to the reg/rec directly, but it should be from switched power on the bike - whatever wire gets switched on when you turn the key on. That takes care of the wires from the alternator.

The reg/rec still has three other wires that need to be connected somewhere. The black wire on the reg/rec goes to a ground point on the frame or engine. The red wire looks like power to the reg/rec and the grey wire is the voltage sensing wire. Most regulators I see don't have separate wires for these as they get everything from one wire, so I would hook them together and terminate them at the same switched main power point that you hooked the black from the field coil to.

To test what you have:
1. Install a fully charged battery and put voltmeter test leads across the + and - terminals. You should have a reading above 12 volts. Note the value.
2. Start the bike and let it idle. Look at the voltmeter reading at the battery again. It should be above the value from step 1. Maybe like 13.5 vdc or similar.
3. Rev the bike up to maybe 4000 or 5000 rpm and look at the voltmeter reading again. It should be somewhere in the neighborhood of 14.5 or 14.7 vdc, but should not go above it. ( I am using approximate ranges here because the specs are not listed for the unit you bought.)

 

[Elder]

Cap, every time I browse this forum, you're out here coming through for the community. Thank you.

The bike actually lived in a cow pasture for about 10 years while I was out doing my time in the Mil. Before that, it was "abandoned" in a different field for an unknown amount of time before making its way to my possession. The harness was Completely shot. I would say I tried to keep it as stock as I could, but I absolutely did not have that luxury... I made it work the best I could figure out and that was the most I could expect from myself on that project.

I'm glad I asked here. This is absolutely Not a wiring configuration I would have just guessed and landed at. I've been dreading this step for over a year, so I'm grateful for the assist. Hopefully with this and a new set of tires, the bike is ready to take for a test ride. You're fantastic.

I'll update and let you know how it goes!

 

[CaptChrome]

Thank you.

You are welcome.

I made it work the best I could figure out and that was the most I could expect from myself on that project.

No issues. You are attempting to bring a dead bike back and that is good enough for me.

I'll update and let you know how it goes!

Please do. This will be important knowledge for the forum. Plenty of people have posted with various regulator issues and there are some tried and true solutions for installing a replacement ground-switched regulator. However, a reg/rec combo that is ground switched and works in the bike would be useful info for a lot of folks. Knowing if this one is the unicorn or not would be valuable.

 

[Elder]

I wired everything together the way you recommended and I'm not positive we're in business, but I'm reluctantly optimistic...

With everything connected and the RPMs up (unsure exactly how high since the tach isn't connected), the voltage across the battery reads around 12.7-13.5. It's not as high as the 14+ that's targeted, but I can watch the voltage drop when running the electronics , but it does come back up. I'm also curious if the Lithium "smart" battery is affecting the readings since it may be trying to manage the voltage output somehow. So for now, I'm back in a holding pattern until I get some tires on the bike and take it for a couple test rides. If it dies a couple miles from the house, I'll have a pretty solid guess why.

More to follow once I pick up tires and test run it.

 

[CaptChrome]

I don't have any experience with lithium batteries in this application and you would have to read up on it to tell if it is outsmarting the troubleshooting here. What was the battery voltage without the bike running?

12.7 to 13.5 volts sounds low for the regulator to be working, but if it is higher than the starting battery voltage, all could be well.