1973, Installing new OEM harness, no power to the black wires (12v pos)

[CB1K]

If there's a thread already on this , please drop the link in comment

First time CB750 owners here. Unfortunately my son and I bought a frankenstein track build. The goal is to get it back to a street bike. It didn't have any lights when we bought it. We decided to replace the custom mess of a wiring system with the new OEM style harness from vintagecb750.com Everything seemed to have a place until I tried to power it all up. Not getting any POSITIVE power to the black wires. but if I connect a tester to the positive post and touch the connectors , the lights work! I'm hoping its something small and stupid but I don't want cause any damage trying to figure it out.

What were working with: All brand new - lithium battery, led signals and headlight, ricks reg/rec, blade fuses, led relay, key switch, brake switch... has original starter solenoid, upgraded points and dyna coils 3 (0hm).. not sure if the starter and alternator are original or repro, all connectors were checked, ground is secure, terminals are tight, battery charged, fuses not blown...

*side note... the bike ran fine before we stripped it down

.... and YES, were swapping to all LED , i know i know, but its my sons first street bike and safety matters more to me than preserving a bike that's far from original.

 

[pickleknuckles]

If there's a thread already on this , please drop the link in comment

First time CB750 owners here. Unfortunately my son and I bought a frankenstein track build. The goal is to get it back to a street bike. It didn't have any lights when we bought it. We decided to replace the custom mess of a wiring system with the new OEM style harness from vintagecb750.com Everything seemed to have a place until I tried to power it all up. Not getting any POSITIVE power to the black wires. but if I connect a tester to the positive post and touch the connectors , the lights work! I'm hoping its something small and stupid but I don't want cause any damage trying to figure it out.

What were working with: All brand new - lithium battery, led signals and headlight, ricks reg/rec, blade fuses, led relay, key switch, brake switch... has original starter solenoid, upgraded points and dyna coils 3 (0hm).. not sure if the starter and alternator are original or repro, all connectors were checked, ground is secure, terminals are tight, battery charged, fuses not blown...

*side note... the bike ran fine before we stripped it down

.... and YES, were swapping to all LED , i know i know, but its my sons first street bike and safety matters more to me than preserving a bike that's far from original.

Do you have any extra brown or black wires in the bucket w that new harness? I'm currently digging into a similar issue on my K4 w new harness and have read that those extras are for UK not US bikes and they need to be jumped somehow to get the black hot, but I haven't found any explanation of which goes to what.

 

[Hisvett]

Double check your Ground Wires......lots of them! I feel for ya, just went through some of the same issues with my '78 because the prior guy put a new harness in but wasn't the correct year. Wire colors didn't match up....had to rely on wiring diagram to get close; the rest I managed to get clues off U-Tube.

Good luck!

 

[bossboy302]

Sounds like quite the project.
I asked 10 people how to route the harness and cables (esp under the tank). Got 8 different answers.
But I do have it correct now, and happy to offer any photos, etc.

 

[CB1K]

Sounds like quite the project.
I asked 10 people how to route the harness and cables (esp under the tank). Got 8 different answers.
But I do have it correct now, and happy to offer any photos, etc.

Are you using stock coils?

 

[CB1K]

Do you have any extra brown or black wires in the bucket w that new harness? I'm currently digging into a similar issue on my K4 w new harness and have read that those extras are for UK not US bikes and they need to be jumped somehow to get the black hot, but I haven't found any explanation of which goes to what.

Yes I do, I seem to be running "12v" power thru the brown wires when key is in Ignition. And Black wires only have power when key is in the ON position. Waiting on response from 4into1 to let me know which harness they sold me (part# 24-4001)

 

[bossboy302]

Yes, stock coils (and all electrical stuff)

 

[pickleknuckles]

Yes I do, I seem to be running "12v" power thru the brown wires when key is in Ignition. And Black wires only have power when key is in the ON position. Waiting on response from 4into1 to let me know which harness they sold me (part# 24-4001)

You think it might be the wrong one? I got mine from 4into1 as well. The extras I have are a Br, Br/W, Bk, and one I can't find on any diagram I've seen that's a Br/Bk. I don't have a battery on it yet. Prob this weekend.

 

[CB1K]

Sounds like quite the project.
I asked 10 people how to route the harness and cables (esp under the tank). Got 8 different answers.
But I do have it correct now, and happy to offer any photos, etc.

upload it all.. lol Coils to harness and ignition, key switch, is my biggest problem. but i have the dynatek 3ohm coils. I think I burned the electronic ignition while trying to get the wiring right, now im unplugging it anytime I work on electrical. Just cant seem to get 12v power (key in 2nd position aka ignition) to Black/white wires like everyone talks about. only the when in the on position. I some how get power to brown only wires.

 

[pickleknuckles]

Yes I do, I seem to be running "12v" power thru the brown wires when key is in Ignition. And Black wires only have power when key is in the ON position. Waiting on response from 4into1 to let me know which harness they sold me (part# 24-4001)

Fwiw, when I put a battery on my K4 w the same harness (#24-4001 - from 4into1 and VintageCB750), the extra Br, Br/W, and Bk were all hot, the unidentified Br/Bk was dead, and I had everything but power to the headlight. I ended up jumping the loose Br/W to Br/Bk and everything worked after that.

Br/W goes to TL1 on the main switch which is hot w the key in the running position.
Br goes to TL2 on the main switch for safety position lights which are the tail on US bikes plus a wedge bulb marker in Euro headlights. You are able to remove the key in this position.
Bk goes to IG on the main switch and the extra loose individual just ended up capped off in the bucket.
Br/Bk...absolutely no clue, but I do know that Br/R (Headlight 7A) and Br/W connect at some point, and since it was the only dead wire I figured Br/W was a safe choice.

 

[Don R]

A hot brown when the key is just in the ignition switch? That does not sound right.
Striped wires have all been through a switch, black to the kill button and black/white coming back to the coils. Do you have a male to male jumper? US bikes might need one where the euro bikes have the front parking lamp.