Overcharging with DIY reg/rec

[D3viousd4n]

Hey everyone,

My 1978 xs650 seems to be overcharging. I'm getting readings of about 15v at ~3000rpm that increase to 16v by 4000rpm. I noticed this occurring after I took the bike out from storage where it was sitting for a few months. The engine is starting and running well, although I haven't taken it for a proper ride this season yet. After noticing the overcharging, I bought a new VR115 regulator hoping that would solve this issue--unfortunately not. I also noticed the main 20a fuse was blown, which I replaced with no change in the overcharging.

I installed a new stator and rotor last Fall that I trust to be good. I'm unsure if the problem lies in the way I've wired the reg/rec, or if there is a problem elsewhere in the harness. Attached are some pictures of the unit and how it's wired into the harness. I've followed Jim & 5twins' guide. Any thoughts?

Image 1: set up during testing.
Image 2: rectifier and battery ground to engine casing
image 3: fuse box & splice into main harness (leaving unsoldered until functioning properly)
image 4: vr115 yellow+orange wire combined as per guide
image 5: vr115 green+black leading to stator connection and brushes.

 

[D3viousd4n]

As I think about this more I realize the only ground connection I have to the regulator is at the inner brush housing of the stator. I have generic metal screws mounting the brushes to the stator housing. Could adding an additional ground connection from my regulator to the engine case possibly solve my problem?

 

[Jim]

The VR-115 regulates by cycling the power going to the rotor on the green wire. It's a rapid pulse of 12v with it biased toward more power (time) when battery voltage is low and less power (time) when voltage is high. Anything above about 14.5v at the battery means very little power to the rotor from the regulator.
Only two things I'm aware of that cause high voltage output. Either a faulty regulator energizing the rotor too much or a bad voltage drop across the ignition switch.
Try this....
Key on. Measure the voltage at the battery terminal AND measure it at the brown wire in the fuse holder. Let's see how much drop you have?

 

[D3viousd4n]

Key on, voltage at battery is ~12.6, at the brown wire ~11.6. Is that within normal?

 

[Jim]

No. The brown feeds the regulator, so what the regulator's seeing is voltage that's a full volt lower than actual battery voltage. The regulator wants the battery to be at least 14-14.5v. Since it's seeing voltage that's a full volt lower than what it wants, it's overcharging. Look in Tech. There's a thread on refurbishing the ignition switch. I'd start there. Best is to get that drop down under .2v or so.

 

[D3viousd4n]

Thanks Jim. I think this is the thread you're thinking of: https://www.xs650.com/threads/ignition-switch-overhaul.46712/

 

[Jim]

Yep. I've never used that thread, so I can't vouch for it. But lot's of people here have used it with success, so give it a go.

 

[Jim]

Btw, this might or might not fix your problem, but it needs taking care of regardless. I'm sure it will help, so get that cleaned up and we'll go from there?

 

[D3viousd4n]

Sounds good. I'm sure there's plenty here that needs taking care of

 

[Jim]

It could also be dirty contacts on the ignition switch connector and/or the fuse holder connector, if it has one. Most likely it'll be a combination of a little bit here and a little bit there. Might as well clean those connectors up also.

 

[Jim]

And you need to get some real splices for your wiring. Twisting wires together and wrapping with electrical tape is just asking for trouble. Get some real splices.

 

[Melnic]

Key on, voltage at battery is ~12.6, at the brown wire ~11.6. Is that within normal?

Brown wire is subject to voltage drop by multiple connections and the ignition switch. Mine was like that and I cleaned it up and it went up a little bit.

I have a thread on my venture to get my XS650 running again when I got it.
When I got it, there was no battery (cause it was failed), Rotor was burnt, Rectifier had an open circuit on one of the 6 diodes so I completely re did everything.

I put the VR115 pulling the old regulator. After I had pulled the original regulator, I took it to work to see how it was regulating and found that it was similar to yours and was regulating to over 16V. There is an adjustment screw under that metal cover that you can adjust the tension on a spring that changes the rotor voltage. I suspect this is a common thing where rotor burns up as it over charges a battery.

If your VR115 is not putting enough voltage to the rotor, you may need to clean up your contacts to get your brown wire voltage up. Ignition switch , some bullet connectors and I think (not sure) also the run/stop switch. It will still be lower than the battery cause connections never are 0 ohm and neither are the thin wires they used.

 

[D3viousd4n]

It could also be dirty contacts on the ignition switch connector and/or the fuse holder connector, if it has one. Most likely it'll be a combination of a little bit here and a little bit there. Might as well clean those connectors up also.

If your VR115 is not putting enough voltage to the rotor, you may need to clean up your contacts to get your brown wire voltage up. Ignition switch , some bullet connectors and I think (not sure) also the run/stop switch. It will still be lower than the battery cause connections never are 0 ohm and neither are the thin wires they used.

I'll start with cleaning as much as I can and see where we get. And I'll get some proper wire splices.

 

[Its been a long time]

Thanks Jim. I think this is the thread you're thinking of: https://www.xs650.com/threads/ignition-switch-overhaul.46712/

I followed that thread. It's really surprisingly simple to strip and clean the ignition switch. I reduced the voltage drop between battery and brown wire to about ~0.3v. I also highly recommend cleaning the kill switch too. It's important to get as much of that voltage as possible onto the ignition coils for the fattest sparks.

 

[Its been a long time]

No. The brown feeds the regulator, so what the regulator's seeing is voltage that's a full volt lower than actual battery voltage. The regulator wants the battery to be at least 14-14.5v. Since it's seeing voltage that's a full volt lower than what it wants, it's overcharging. Look in Tech. There's a thread on refurbishing the ignition switch. I'd start there. Best is to get that drop down under .2v or so.

I never thought of it. But if the brown wire voltage is the reference voltage for alternator excitation, it makes perfect sense. Getting minimum voltage drop on the switched live brown wires can only be a good thing. But that's a great point about voltage and alternator output.

 

[arcticXS]

I have recommended installing relays for power to coils and headlights in previous discussions. What about using that "brown wire" to control a relay connecting battery + to the regulator using short, direct wiring?

 

[Its been a long time]

I have recommended installing relays for power to coils and headlights in previous discussions. What about using that "brown wire" to control a relay connecting battery + to the regulator using short, direct wiring?

That's a good idea too. I have my ignition system fed by a 10amp fuse from the battery through a relay. I switch the relay with the red/white wire from the kill switch.

 

[arcticXS]

That's a good idea too. I have my ignition system fed by a 10amp fuse from the battery through a relay. I switch the relay with the red/white wire from the kill switch.

Exactly. When pulling my XS out after several years of storage, it wouldn't start. The voltage at the coils was really low. So I cleaned the ignition and kill switch, then installed a relay supplied directly from the battery using a 2.5 mm2 wire. No more voltage drop . On my Ducati ST2, I installed 2 relays for headlight high/low beam. Also worked like a charm.

 

[jetmechmarty]

How to splice wires:

 

[D3viousd4n]

I removed ignition switch, kill switch and fuse box connections and prepping for cleaning.

My ignition switch has a uniform body, and I’m not sure it can be disassembled. I’ve gotten the lock cylinder out of the main housing but it doesn’t seem like I can get to any of the inner workings. The only identifying markers I see are “RT2”

I assume a replacement is necessary