Electric voltage drop when turning kill switch on/off or using horn

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Hey all, got an electrical issue that I don't understand. No electrician myself so hoping someone here might be able to explain what is happening/what I am doing wrong.

Bike info:
Bike is a 1975. Running stock alternator with a Boyer electronic ignition. Kick start only with a lithium ion battery. Built the wiring harness myself so it is far from perfect but has worked for two years now. Recently redid all the wiring connections due to this issue (hoping that would fix it and I wanted to replace the cheapo connectors I had used with better bullet connectors). Unfortunately that didn't turn out to be the solution :doh:

Issue:
When I turn the ignition switch on and then toggle the stock kill switch, I get a 4-6 volt drop for a second. Same thing happens when I sound the horn. I have a volt gauge connected to the brown output wire from the ignition switch and this is where I am seeing the drop occur. So for example, with ignition on, I toggle kill switch, gauge back light flashes 2-3 times, voltage drops from 12 to 6-8 volts for a second and then bounces back up to 12 volts. Same thing happens with the horn.

Troubleshooting I have done:
Disconnected my ignition wire from my 6 blade fuse box, issue goes away when horn is used.
Disconnect all outputs from 6 blade fuse box except ignition feed, issue remains.

Is it possible I have an issue with my Boyer ignition box? Seems like the obvious culprit but not an easy/cheap thing to swap out. Haven't tried to start the bike because I don't want to button everything back up and have it still not work due to this gremlin.

Shoot me any questions you might have as I am sure I missed some important details.

Here is my current wiring schematic (not shown is a line from "lights on/off" to running tail light):
wire_schimatic_xs650.jpg
 
When you toggle (turn to run) the kill switch, the initial step is to charge the coil. That and energize the Boyer box. I've never checked it, but it sounds normal to get an initial drop in voltage like you describe... at least to me.
Same with the horn. The horn draws a pretty large (relative) current when it's energized. I would expect a large voltage drop if the alternators not running.

If we're to assume your drops are excessive, then it sounds like a weak battery to me.
 
Thank you both for the info! Makes me feel a lot better lol This was making my head hurt trying to figure out what could be the possible issues.

Is it safe to say I should put it back together enough to see if it starts to know if there is actually an issue?

Again, really appreciate the timely help!
 
If you still have the switches off I think it would pay you to strip the kill and ignition switches to clean the copper contacts. It's very easy to strip and clean both of them and it definitely improves the voltage on the bike's electrical systems. There's some small steel springs in there. I had to replace broken and corroded ones. I bought generic springs of the right size from eBay.
 
the red wire from the regulator needs to go to the battery. on you diagram the regulator (red) is going to the brown wire circuit.
 
where is the coil circuit on your diagram?

Yes Sir I was also Scratching my head on that It is a bit sensitive since the Boyer coil cant withstand power up for prolonged time without bike running according to their instructions.
And power up here ..can damage it ..

They used to say in electronics not sure the Translation is OK

quickly connected half burns
 
Yes Sir I was also Scratching my head on that It is a bit sensitive since the Boyer coil cant withstand power up for prolonged time without bike running according to their instructions.
And power up here ..can damage it ..

They used to say in electronics not sure the Translation is OK

quickly connected half burns
The kill switch as shown can be used to turn power onto the bike without frying the Boyer Bransden system or the ignition coil. I do that nearly all the time on mine.

Assumed that the power fed to the BB also feeds the coil. That's standard BB system wiring. Though, yes would be nice to see the ignition coil on there.

Looks a nice simple system set up to me. I also need electric start, but not everyone does.
 
the red wire from the regulator needs to go to the battery. on you diagram the regulator (red) is going to the brown wire circuit.
No, red from the Rectifier goes to the battery. It's the rectifier that supplies power, not the regulator. He's drawn it correctly.
 
where is the coil circuit on your diagram?
Yes Sir I was also Scratching my head on that It is a bit sensitive since the Boyer coil....
Assumed that the power fed to the BB also feeds the coil. That's standard BB system wiring. Though, yes would be nice to see the ignition coil on there.
I assumed that too.
Maybe call it a "system" instead of just the box? All Boyer parts are contained within the system. Of course, then you'd need another diagram for ignition..
Perhaps the OP has that drawn also. Perhaps he knows what he has and thinks we're being picky? ;)

1736093385294.png
 
Confusion is the regulator should have 3 wires not 4. Br, Gr, B. Having a red wire is unusual and not factory
View attachment 341993

VR-115 has 4 wires. One is power to feed the rotor. The other is battery sense for regulation. For our purposes, they get combined into one lead. I suspect that's what he's using, a VR-115 or equivalent.

From the reg/rec thread in Tech.
1736098963934.png
 
The kill switch as shown can be used to turn power onto the bike without frying the Boyer Bransden system or the ignition coil. I do that nearly all the time on mine.

Assumed that the power fed to the BB also feeds the coil. That's standard BB system wiring. Though, yes would be nice to see the ignition coil on there.

Looks a nice simple system set up to me. I also need electric start, but not everyone does.

Aehh --it depends

There are 2 different wires
One to coll Red / White going to orange
And Red to box
Maybe not any difference since both should have 12 V

But as I see it 2 different BB being experts would have used one if not any difference
High Power ?? Risking frying one Wire ? ---Just speculating
Or maybe just for the possibility using Kill Switch grounding Coil

If I recall, right you are using a relay that changes is perhaps

BB warns for that not having power on the Coils prolonged time fex Kick starting .. Can save 50 Euros ...draw it in the circuit before powering up
We can have a look

1736098025490.png
 
Aehh --it depends

There are 2 different wires
One to coll Red / White going to orange
And Red to box
Maybe not any difference since both should have 12 V

But as I see it 2 different BB being experts would have used one if not any difference
High Power ?? Risking frying one Wire ? ---Just speculating
Or maybe just for the possibility using Kill Switch grounding Coil

If I recall, right you are using a relay that changes is perhaps

BB warns for that not having power on the Coils prolonged time fex Kick starting .. Can save 50 Euros ...draw it in the circuit before powering up
We can have a look

View attachment 341994
Not that it really matters. But there's just one white/red wire to the ignition system. BB splits the single red/white wire to feed 12v to the BB box and to the ignition coil. The 12v comes from one red/white wire.

You are right about me using a relay for the ignition system. But I wired it the same as the original system.

I always use the kill switch off when working on the bike with the main ignition switch on. I understand the ignition coil should not be powered up continuously for more than maybe 10 minutes or it will get very hot. Using the kill switch takes power off the ignition system but leaves all other systems powered up.
 
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VR-115 has 4 wires. One is power to feed the rotor. The other is battery sense for regulation. For our purposes, they get combined into one lead. I suspect that's what he's using, a VR-115 or equivalent.

From the reg/rec thread in Tech.
View attachment 341996
Yep I said unusual, not factory. Might create confusion if not known it is a VR115.
Unless the OP states what is used a guess or a supposition works.
 
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