CB750 wiring help please

got them loaded - sorry as it is a jumble of stuff to look at

again, all and any help appreciated

cheers
 
The last photo is the diode that works with the neutral safety switch and starter switch. Allows you to start only with neutral or clutch pulled in....

You need to get a schematic to see what the others are...
 
Thanks M . . .

There are no wires/plugs on the new harness that fit or go to the diode except the red plug. The red plug will certainly not fit the old diode. All the other plugs on the harness are white and this one is red and has five wires.

I've been looking at the schematics and figure it out. Was hoping that someone here might have replaced their loom and had the same experience.

Green/red & yellow/red should attach to the new black & yellow/red wires - connectors are wrong and will have to swap one set around in order to connect.

The free hanging wire (with the small little black squares on it) seems to hang freely from what I understand from schematics I've looked at and photos. But, doesn't seem to make sense to me . . . why would there be a free handing wire??

The red plug is the unknown . . . . no plugs to connect to.


Thanks again for reading!

Cheers
 

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The green wire is a ground. Likely a spare and not used. My '78 750K has one or two of them as well.

Your schematic is a bitch to follow! I've got a color one in the Clymer manual that's a little easier.
For the "black" and "orange/red" wires... is your starter relay hooked up? It looks like they might go there, if it's not already wired up and functioning.
The red plug is a stumper, as the schematic doesn't show plug color. Where does it come from, and what color are the wires coming out of it?
 
If the new harness doesn't match my old one nor the wiring diagram, I'd be checking to see I got the correct harness first off.

Edit: On the diagram there is only one yellow/red wire and that goes from the 15A fuse to the cut out switch at the handle bars. so assuming the harness and diagram are correct it should be part of that circuit.

That diagrams a tester for my aging eyesight.
 
Here's a 78 CB750 Schematic in color. Shows the diode and all....

See if it helps.

You may have the wrong harness (Newer)

the last pic in your post shows a diode and the connector for that diode.....Yet you said it didn't fit...looks like it fits...
 

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Thanks guys for the help.

Sorry about the schematic - I find most hard to follow. Printed off a few different ones to try and figure this mess out. Swamped at work and home the past couple days (preggers wife who is going through a wicked "nesting" phase and has jobs around the house coming out the using-yang).

The wire harness is correct as far as I know - ordered the correct year and it was labeled as such.

M - the last photo is off the old harness and diode - I disconnected it to show. Not sure what replaces it.

I'll get a photo up today of the colours coming out of the red plug. Going to have a look at the schematics I printed off last night and will report back tonight.

Thanks again fellas - hoping to get this resolved with your help!
 
What year bike? Looks like the harness that I bought, mine is for a 1975 CB750k5.

That red plug is for the starter safety switch, that forces you to pull the clutch in to start the bike.


The plug looks like this:
 

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bigring said:
It's a '73. I believe that the same harness is good for '73's to '75's.

Clymer shows the '70-'75 utilize the same harness ;)
And Budlite looks to have nailed it. A quick check of the Clymer schematic seems to correspond with the wire coloring.
 
Thanks for all the input guys - really appreciated. This noob is learning lots. Cheers.

yup, that's the plug.

Spent some time this afternoon going over the schematics from the shop manual trying to figure this out. K3-K7 use the red plug, 76-78 (as far as I looked) use the two wired diode.

My bike is a '73 but has a '76 engine. Before ordering the harness I checked the switches (not carefully enough) and figured that it was just the engine that was put in and the PO left the '73 switches, etc. (everything else on the bike is '73). However, I was wrong and now the two wired dioden makes sense.

So . . . . now what do I do? Harness is mostly already set up. Can I use the '76 diode by trimming off the wires from the red plug (black, yellow/red, dark green) and kept the two that work with the diode (green/red and light green/red)??

Cheers!
 
I really think you can (in my best/or worse NYC acsent {<spelling}) "forget about it".........

And, I'm originally from Delaware..........................

Just that you will be able to start it in any gear, and if you do ......that might not be good.

'Secially if it shuts off in traffic and you start it, and it decides that, that brand new 2013 Camaro needs to have a nice big dent and some of your paint on its hood.
 
Cutting the wires from the red plug not needed to go to the diode and connecting (green/red & light green/red) the others - will that make it work, will the engine start only neutral???
Don't want to become a hood ornament! ;)

Figured out the rest of the wiring questions:
  • new harness - black & red/yellow go to the solenoid - hooked to the green/red & red/yellow wires [black replaces green/red]
  • green free (with black squares) is another ground - as stated above - and can hang free

Miss anything?

Thanks fell'ers and cheers!
 
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