Topic: 76 CB750F Keyed ignition and tach wiring issue

[toadm]

Hello and happy new year. Rewired bike adding:
- Munit blue
- Motoscope speed sensor
- Motoscope mini
- Motoscope combi frame with LEDs
- Speedmotoco headlight
- LED tail lamp
- Shorei lith ion battery LFX14L2-BS12
- Ricks lith ion compatible reg/rect

This is my first time doing it all and by all means an amateur 2 issues that I could use some help
- Bike starts with keyed ignition off. Ive checked switch wiring multiple times
- Im getting 12v at the end of the yellow tach wire from motoscope mini that I understood attaches to the blue or yellow wire at coils. And wasn't sure if this was supposed to happen. Understood it is not.

Here is wiring diagram. Yes, I know I should have done much better job at pulling thru standard color wiring.

Thanks in advance

[toadm]

First problem is: the BLK wire FROM the Motoscope Mini is to wired to Ground, you have it connnected to switched power.

This confuses lots of people. In Honda standard colors, solid BLK is a positive 12v source whereas normally we consider RED positive and BLK negative.

As for getting power on YLLWfrom the Motoscope, changing the BLK should solve that issue. Make the corrections and report back.

Hello and thank you. Forgive me, I'm not sure I follow. Are you saying that the BLK wire from mini should not be connected to GND/earth? Just do a switcharoo with RED? I have it this way only because I was following the instructions supplied - BLK to vehicle earth. At least that is what I thought - lol. See attached.

[toadm]

No, I am saying that BLK should be run to earth. But from your diagram it connects to other “switched circuits. If I am mistaken, then disregard.

Gotcha. It's likely my poor diagramming. I have BLK wire from mini connected to same earth GND as Motoscope combi frame LEDs

[toadm]

So that we are clear, where I circled in Yellow is what concerns me. You “show” that BLK from Motoscope is connected to a common BLK that is powered. Is this an error in your diagram or in your wiring???

I'm sure this is error in my wiring and perhaps the root cause of my problems? After you responded, I questioned everything I did. Was treating that BLK wiring as a neg ground circuit. The place you circled does have junction / connection to frame at front of bike. Am I right in thinking this is all wrong?

[toadm]

Solid BLK in your harness is switched 12v positive. The MotoScope uses it as negative. Splice a solid GRN to it as that is the stock Honda earth circuit color.

Thanks. Will update and report back. Have a few things I screwed up here doing same.

[toadm]

If you want to update your drawing and post it, I’ll happily look at it before you wire it up to see if anything is wrong.

Thank you. Very helpful explanation and much easier way to understand it. Taking you up on reviewing updated drawing. Here it is. Thanks so much.

[toadm]

Thank you. On the wire color, yeah, I'm this close to starting over using standard colors but now on mission to just get it running again so I can ride it. Will report back once I get it all sorted and back together. Thanks again.

[toadm]

Happy to report that the fixes to the wiring all seem to be working. I didn't change connection to reg/rectifier but will. Tach works. Also confirmed with motogadget that having 12v at the yellow wire correct and confirmed that works when engine running.

My only item that I still want to resolve is that I don't want my moto mini, lights...powering up as soon as battery connected rather only when key on. Believe I can control all that thru settings in munit app. Correct me if I'm wrong. Or if anyone else recommend an added power kill switch between battery and munit to prevent bat potential drain.

Thanks again Cal for help.

[toadm]

The moto mini gauge should not become active until the key is ON position as you have it drawing power from AUX. when you say “lights” do you mean the gauge lights or the head/tail lights?

Currently both lights and mini power up when battery connected and key is off position.

[scottly]

When the key switch is off, the system should be turned off. What key switch are you using, and how do you have it wired?

[scottly]

Also, you have the second green reg/rect wire connected to the field coil green. They should both be connected to ground, not just each other. If you do have the key switch wired as a simple on/off switch, my WAG (wild assed guess) would be a backfeed of sorts through the reg black wire, sufficient to trigger the m-unit into turning on.

[toadm]

When the key switch is off, the system should be turned off. What key switch are you using, and how do you have it wired?

Hi. I am using an aftermarket 4-wire switch from Carpy: https://carpyscaferacers.com/shop/shop-our-store/motorcycle-parts-accessories/honda-cb500-cb550-cb750-parts-upgrades/ignition-switch-assembly/
I am only using 2 of the wires. RED to bat + and BROWN to Lock input on Munit. Unused wires are BLK and BROWN w/white stripe. To troubleshoot, I have disconnected key ignition switch entirely from system and still getting power to mini and lights. Which leads to problem elsewhere. BTW - if I incorrectly wired ignition, please let me know.

Also, you have the second green reg/rect wire connected to the field coil green. They should both be connected to ground, not just each other. If you do have the key switch wired as a simple on/off switch, my WAG (wild assed guess) would be a backfeed of sorts through the reg black wire, sufficient to trigger the m-unit into turning on.

Can you help my amateur brain understand this? When you say second green wire, are you referring to the green from the rectifier to the white plug that connects to green wire to the stator? See image for reference. And if answer is yes, how would you do this / do you have a reference?

Thank you!

[toadm]

Scottly - I think I am picking up what you are putting down on green wire. Reading this thread again: http://forums.sohc4.net/index.php?topic=91389.0

Going back in to resolve and will report back. Thanks again

[scottly]

The red switch wire is connected correctly, but the black switch wire should go to the Lock input, not the brown wire.

[toadm]

All problems resolved. After following all recos was still getting power to the mini. After tracing wires and troubleshooting, turns out my regulator/rectifier was broken. It was probably fried along the way with my bad wiring job. Replaced, and all is well in the world. Everything functional. On to the next problem. Thank you all for helping me resolve.