Topic: Help with Wiring

[sandersgtn]

I need help understanding some of the un-used wiring for my 1975 CB750 K.  Previous owner has removed many items. I have looked at several wiring diagram to try to determine what these wire are for.  Thought someone who is more familiar could help.  See attached photo.
- the top 5 wires are (2) light green, (2) light blue and (1) brown.  I would guess signal lights.
- next 2 wires are black and gray (signal light blinker)?
- next 3 are (2) brown and (1) red.  No clue.
- next 4 are (2) orange and (2) dark green.  No clue.

Can anyone identify what these wires are supposed to do?  I do not plan to reinstall the signal lights.  But, will need to wire my headlight, high beam light and speedo/tach lights.

Thanks for any help?

[Spanner 1]

Lets see...  top group of wires would be to tail light ( brown ) and right side turn signals ( lgt. blue ) and ground ( green ). That brown needs to be connected back to the ign. switch if you want a tail light btw.
Next, black and grey would have been connected to the signal blinker box, brown to tail light or to/from tail light fuse, red from/ to main fuse or ignition switch. You would have to trace these last browns and red thru' the loom to really verify what they connect. Orange and green would be right side turn signals... good luck.

[DH]

maybe this will help as well...

[sandersgtn]

I thought I had posted this message, but couldn't find it.  Reposting...

A few more questions:
1. I thought I had bought an OEM kill/start control, but I find some differences with the wiring diagram.  The only two wire that switch on/off continuity with this control are black/red and brown/white. I have found the black and black/white wires in the harness where the previous (non-OEM that works) kill switch was wired in.  So, I will just connect these.  Don't see any issue here.

2. The "OEM" switch also has a rotary left/right engine off switch.  I can't find any combination of wires on my switch that go on/off continuity for this left/right engine off switch.  Any thoughts?  Otherwise, I will ignore.

3. My "OEM" switch has 6 total wires:  black, black/white, black/red, green/yellow, yellow/red and brown/white. Black/red and brown/white will be used per the above.  The black and yellow/red wires show continuity with the start button (OK).  The black, black/white and green/yellow wire have continuity all the time - this doesn't make sense to me unless these are just sources of switch hot wires for other purposes.  The wiring diagram shows three wires in the start circuit - black, yellow/red and black/red (I think).  I understand the first two, but not the third.  What is this third wire for?

4. The existing non-OEM start switch has 3 wires connected to a blue/red, yellow/red and light green/red in the wiring harness.  This doesn't match the wiring diagram but does turn the starter.  The wiring diagram shows light green/red as the neutral light.  Guess I will have to trace the correct wires in the harness.  Any thoughts?

5. Except for the above corruption and some turn signal wiring that has been cut out, I believe my harness is more or less complete and original.  I'm thinking to remove other wires that I'm not using to simplify.  Should I just leave them for future use or cut them out?

Thanks

[TwoTired]

Have you looked in the electrical FAQ.
It has the standard color code convention used by the Hondas of this era.

http://forums.sohc4.net/index.php?topic=1012.msg188242#msg188242

If your controls don't follow these conventions, then you will have to find or make a translation map to determine the correct connectivity to a standard Honda main harness.

You can use an ohmmeter to determine which wire goes to which switch contact internal to the control.  If not, then you have to take it apart to know what the control is doing with each wire connection.

[sandersgtn]

All.  Thanks for the help.  I decided to simplify the problem by buying a correct wiring harness and left side control.  Now fewer problems.  I have a mis-match with a black/red wire from right side control.   Can't find a match.  Does anyone know where this goes?

Thanks

[Bodi]

Black/red goes to the "HEAD" fuse. This is switched in the right pod - to black when the start button is not pressed. With it pressed, black is only connected to yellow/red to the solenoid. That means the headlight is turned off while starting. If you don't have that wire or that double throw start button, connect black/red directly to black so your headlight works.

[sandersgtn]

Sorry,  I don't know what the "head" fuse is.   Are you saying that the black/red is the "hot wire" to the headlight and supplies both high and low beam, but is switched off by the start button when starting?  I think I found matching connectors for all but this black/red wire.  From earlier posting (before new wiring harness) below:
3. My "OEM" switch has 6 total wires:  black, black/white, black/red, green/yellow, yellow/red and brown/white.
So, if I can't find a matching black/red, I should find the black lead to the headlight and connect to it?  Do I have it right?
My headlight is non-OEM, but I have figured out the the ground/high/low and plan to connect to harness (I guess technically to left side control) with some harvested correct colored wires from old harness.

Thanks

[sandersgtn]

I spent some more time trying to debug the remaining wires and I think I now understand your input on the black/red wire.  I do have a double throw off/on/off switch on the right control.
I still have a few questions about remaining wires.  After connecting all the matching wires between controls and harness (except headlight oil/neutral/etc indicators not connected yet) and setting aside wires I know I will not be using (signal lights/flasher relay), left with the following (see attached photo):  blue, green, white, brown/white, 2 brown/red, black brown and green/red.  The blue comes from OEM left control.  All others are from main harness.  My guesses are as follows:
blue - high beam.  My headlamp is non-OEM with three wires (low/hi/ground) plus an amber running light.
green - ground.  Only ungrounded item left I think is headlight.
white - low beam
brown/white - switched instrument lighting, but I think my speedo/tach are already connected to other brown white.  Guess I could use headlamp amber running light.
2 brown/read - fused headlamp power, but I don't know what to connect to.
black - switch power, don't know what to connect to.  I already have switched power connect elsewhere.
brown - tail light power.  Don't know what to connect to.
green/red - neutral switch to indicator.  I have a non-OEM LED indictor cluster with 3 lights.  Need to find neutral (red/green) and high beam.

Any help decoding these will be appreciated.

Also, I note that my speedo has a little red light that could be hi beam.  I need to double check my tach to see if it also has an indicator.  I bought them separate from the bike, so may not be same year.

Thanks for any help you can provide.

[Spanner 1]

Wait !.. is this the same poster from 4 years ago asking the same question ? Is this a SOHC4 Forum reply delay record ??

[sandersgtn]

Yep, same project, new set of wires to diagnose.  I abandoned the old butchered harness and bought a new "OEB" harness.  Still had some wires I couldn't identify as they don't show up on the wiring diagrams.  I think I have them figured out.  Thanks

[Athame57]

I looked at the 'birds nest' under my tank and decided to let the professionals at the workshop fit all my new switchgear....I'm about to receive a new harness...I bet I'll let them fit that too!

[sandersgtn]

Thanks for feedback.  I bought a new "OEM" wiring harness and was able to correctly connect 90% of the wiring.  The remaining 10% was  where I didn't have complete matches all in the headlamp between the harness, controls, headlight and idiot lights.  It's because while both the controls and harness are supposed to be "OEM," they are really reproductions that may not exactly match the original.  I found a local Honda certified tech with experience on the older CB750s to debug the last 10% where I had some uncertainty.