CB750 Wiring Issues

[Oddjob]

No I don't think you're understanding it correctly Sean. I can't see a brown/red at all unless that wire coming in from the 7A fuse is the brown red, just looks brown to me on my PC. Either way that fuse get's it's power from the brown/white circuit, (it's an internal connection inside the loom) which is powered by the headlight on/off switch,(which gets it's power from the standard black wire feed on Hondas) the brown/white circuit feeds the bulbs in the speedo/tacho, feeds the ignition switch so it powers the brown wire when the switch is on, which in turn powers the fuse for the rear light and also runs a feed down to the indicator switch so that when the indicators aren't working it powers the running lights the yanks got. As well as of course feeding the main light fuse due to the internal connection.

[royhall]

Thanks for all the input to this thread it's been a great help.

I spent two full days almost pulling my hair out with frustration. I had everything functioning but just couldn't turn off the headlight, nor were the lights running through the 7A & 5A fuses. Part of the problem was the brown/white connection going to the 7A headlight fuse (brown/red) was female to female so I ignored it. I went to the lockup and brought back the original harness, it's knackered but still as it was taken off the bike. On the female to female connection was a 50mm long male to male connector, mystery solved. After connecting that, the return from the fuse box black/brown connects to black/brown to the dimmer.

I now have fully and correctly functioning electrics. After two days off and the help you guys gave, the penny dropped straight away. There is no neutral position on the dimmer, no idea what that was all about (the diagram is wrong here, on low it should show brown/green connecting to white). There's only one position on the indicator switch so orange/white and light blue/white remain unused. The brown cable for the buzzer is missing completely, but I don't need to worry about that. I have tested every function on the bike including power to the coils turning on and off with the right hand kill switch. I even turned everything on and removed the fuses one at a time to double check it kills the correct things.

I hope the above explains the situation as it's pretty hard to convey what's going on with electrics, if I missed something just ask. It's all a bit birds nest in the headlamp just now along with some bad connectors. But now it's all connected I will go through it one cable at a time and make everything good. I will be glad when it's all buttoned up and the headlight is on to be honest, it's been a bit frustrating.

Once again thanks for all the help

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[taysidedragon]

Good news Roy. Always a relief when things fall into place and work as they should. 

[Spitfire]

Pictures like that one always look scary to me !

Cheers

Dennis

[Johnny4428]

Very well done Roy! I remember when I did mine with the new harness, connected up everything and when I activated the left indicator the rear right lit! 🥵🥵 but one by one I got there. Very satisfying when everything works then.

[royhall]

To be honest, any time you avoid smoke and blown fuses is a win. Don't think I will be taking up auto electrics any time soon.

[royhall]

Although all is now well, a mystery is still lurking in there. There's a brown wire that runs from the 5A fuse to the back light, that's the feed to the rear light not the brake light. That brown wire is connected inside the loom to a brown wire that runs into the headlight bowl, it has a female connector on it. I have left this wire unconnected. For what purpose would a rear light feed run to the headlight area, it's also not shown on any diagrams. Pretty sure I haven't missed anything, but that said it's been put in there for some reason? Another mystery to keep you up at night.

[Johnny4428]

Hi Roy! Anything to do with parking light? Second position on ignition switch.

[royhall]

That was my first thought, but what does it connect to, and why isn't it on the diagram. Incidentally, I did test the ignition key in park mode and the rear light comes on as expected.

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[McCabe-Thiele (Ted)]

That was my first thought, but what does it connect to, and why isn't it on the diagram. Incidentally, I did test the ignition key in park mode and the rear light comes on as expected.

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You mention the rear light works in park mode what about the front side lamp?

[Johnny4428]

That was my first thought, but what does it connect to, and why isn't it on the diagram. Incidentally, I did test the ignition key in park mode and the rear light comes on as expected.

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That’s same as mine, I didn’t have anything to wire up to at the front end, no side light. I can only assume park light was wired to running lights which these had initially.

[royhall]

That was my first thought, but what does it connect to, and why isn't it on the diagram. Incidentally, I did test the ignition key in park mode and the rear light comes on as expected.

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You mention the rear light works in park mode what about the front side lamp?

Don't have the facility on my replacement indicators for that Ted. I think it's staying unconnected.

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[McCabe-Thiele (Ted)]

If your headlamp has no facility to fit a side lamp would it be sacrilege to fit a separate subtle LED lamp?

[SeanFD]

Although all is now well, a mystery is still lurking in there. There's a brown wire that runs from the 5A fuse to the back light, that's the feed to the rear light not the brake light. That brown wire is connected inside the loom to a brown wire that runs into the headlight bowl, it has a female connector on it. I have left this wire unconnected. For what purpose would a rear light feed run to the headlight area, it's also not shown on any diagrams. Pretty sure I haven't missed anything, but that said it's been put in there for some reason? Another mystery to keep you up at night.

If you look at that thematic - done by one of the guys on the US site - I posted up above, there is a brown wire running from the ignition switch which branches off backwards BUT also has a branch going to the headlight bucket with an unused female connector at the end.

[Oddjob]

If you replace the headlight at some point in the future and you get one with a parking light or side light at least you know where to connect it to. The existing headlight halogen or that god awful big normal bulb?