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

[calj737]

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.

[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.

[calj737]

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.

[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

[calj737]

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???

[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?

[calj737]

Correct, that is wrong.

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.

[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.

[calj737]

Make sure you understand a few things: every switch input to the mUnit is a “ground”. Every output is now 12v+. Stock Honda colors are a bit confusing to US convention.

If you activate a handlebar switch, the right side of the mUnit should show a light on that circuit to let you know you’re correctly triggering the circuit. Power to each component is running directly to it from the mUnit.

Never send 12v to the left side ports for the switched circuits. You can smoke that thing (mUnit).

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.

[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.

[calj737]

Ok, after un-double-crossing my eyes twice, everything looks fine. Your choice of color schemes made the whole thing a bit of a challenge when I’m very accustomed to Honda colors. But that is fine.

The ONLY thing that gives me any pause… you ran from the Reg/Rec the sensing wire into to LOCK. That does work, it’s just not where I would tap for battery performance. Normally, I use one of the AUX ports to feed the REG side as it provides a slightly better assessment of the draw on the battery on the “use side” versus the “feed side”. But again, no big deal, you’ll be fine.

Bear in mind, any Li battery will not have the nuts to sustain testing and wiring and troubleshooting. Use a donor battery until you’ve got everything sorted, then replace with the Li battery. You’ll drain that pretty quickly and could potentially damage it.

Let us know how it goes from here-

[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.

[calj737]

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?