Topic: Differences in wiring harnesses?

[Toxic]

Long story made short is that my bike tear down is going smoothly until I get to the main fuse and it is blown.  Not a big deal, but the PO wrapped the fuse with cigarette foil to by pass it.   Now wiring is not my strong point so I was going to replace the whole harness. I don't know what damage if any was done because of this.  Chasing a short in a wiring harness can be very teadious.

My bike is a stock 77 that I am going to use to build my project.  I have a 72 frame and the engine is a 76 CB750. I can find a NOS harness for a 73-75 but are there any differences?
The engine number is 2551754 which puts it right before the 77's came out, I believe.

I was going to use the wiring harness on the 77 donor bike but now I'm thinking I should replace it with a NOS for the 76 engine.

I was going to do the wiring towards the end anyway and look into an electronic converstion.

Is there any reason I couldn't use a 73-75 harness or should I continue looking for a 76?

Thanks in advance

Gary

 

[Toxic]

I don't know about you guys but this is the last thing I wanted to see. What a dumbass.

[Toxic]

Visually the wiring looks fine except for this green wire that is running over the left coil.


My Clymer manual does show a different diagram for a 76 and a 77 but having stared at them for over an hour, I can't spot any differences.

Well hopefully I have provided enough info so you can give me a little guidence here.

[Jonesy]

The only thing I can think of off the bat is (others please chime in and correct me) the starter safety unit circuit setup- it was simplified in later models. The '73 used a module that was mounted on the electrical tray, while the later ones used a diode.

[Toxic]

I see a diode in line with the clutch safety switch on the 76 and 77.

So my options as I see them are:

-stick with this harness and try and diagnois it. Not appealing
-get a NOS harness for a 76 since that is what the engine is.
-or get a NOS for a 77 since I will be using the sub-systems from the 77donor bike.
( handlebar switches, headlight and tail light etc. )

[scondon]

The engine only has three connecting points(alternator, oil pressure switch, and neutral switch) and these remain constant through the years. Shouldn't have to worry about matching harness year to your engine. Most of the harness differences play out at the headlight where all the controls plug in. Figure which year front end and controls you want to use and try and match accordingly(provided there are any differences in harness years on K models).

  I only know the F model harnesses so afraid I can't be of much help

[Toxic]

Well the donor bike is a 77.
I don't mind doing basic wiring to get the subsystems to work.
My main concern is that the important stuff like engine connectors, starter relay, regulator, etc be the same.

Thanks for the info, much appreciated

[swan]

Take a look at Partsnmore's replica wiring harness. It is reasonable ($75?) and is a fresh start for your Frankenbike.

[SOHC4 Cafe Racer Fan]

K7 wiring harnesses are hard to come by (speaking from experience).  You'll probably have better luck sourcing a K2/K4/K6 harness and retrofitting any equipment from the donor bike.

[Toxic]

Good advice, thanks.
I think I will order the partsnmore harness for 75 bucks.