Working through a rolling restoration on my CB400SF – it runs, but the existing wiring harness is a bit of a pig – years of bodge jobs from previous owners leaves me with constant issues with headlight/taillights failing, but generally everything else seems to run fine.

I’m planning on some major changes – stripping it down to the absolute bare essentials, new headlights, handlebars, ditching the indicators, relocating the ignition key switch, and cleaner wiring/minimal speedometer/tachometers to go with it all.

With this all in mind, I’m thinking that instead of trying to adapt the existing wiring harness I might as well completely re-wire things from scratch, based on this article http://www.bikeexif.com/motorcycle-wiring and this diagram:



I.e. – running basic accessories of headlight, taillight, horn, charging system, speedometer & tachometer, along with the water pump and radiator fan hard wired to always run.

With this all in mind, does anyone with a better idea of electrics & these bikes have any comments/pointers for me to bear in mind?

Cheers

No where on that schematic do I see any sign of an ecu that controls the ignition system , I am no auto electrician but I think if you are going to rewire your bike using that schematic you are doomed to failure.
I think your best bet is to try and find a wiring loom on that internet site

Be careful if you junk the indicators . Post 1986 it is an mot requirement. It depends then on the mood of the tester. Better to include the wiring even if you don't use them, just in case you need to replace them quickly.

If you have the fan hardwired on it would be seriously over-cooled. And the water pump isn't electrically driven....

I'm afraid I agree that it's not a brilliant idea.

As pointed out that wiring diagram is not a lot of use to you as it applies to an older bike such as a Harley or older Honda CB750 which has points ignition rather than a CDI. Also the circuit for the fuel pump & relay is missing.

If you want to minimise your wiring then you will have to find a copy of the correct CB400 wiring and work out what you can eliminate - you'll be surprised how little you can remove on a modern bike......

Thanks guys.

Having gone deeper into the wiring diagrams I think I'll just repair the existing harness instead of rewiring - don't want to turn a running bike into a wiring nightmare!

Thanks for the input though, much appreciated.