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SOHC.co.uk Forums => CB750 => Topic started by: cb750stu on July 08, 2013, 01:19:32 AM

Title: Wiring Loom question ??
Post by: cb750stu on July 08, 2013, 01:19:32 AM

Hi Folks i need to extend quite a bit of my wiring loom so i can fit all my electrical bits under my cafe seat,
I am away to order some different colour wire so what size and what amps do i need ie 15 amps 27 amps etc ???

Regards

Title: Re: Wiring Loom question ??
Post by: Bryanj on July 08, 2013, 08:59:05 AM

If yoou want to move the parts a long way you need to overspec the wiring size to stop voltage drops due to length especially on any wiring to battery or rectifier

Title: Re: Wiring Loom question ??
Post by: cb750stu on July 08, 2013, 05:36:06 PM

There not getting moved far just from standard position to under the seat maybe 10 " !!!!
Cheers

Title: Re: Wiring Loom question ??
Post by: Bryanj on July 08, 2013, 06:24:48 PM

Thats a long way in volt drop language mate

Title: Re: Wiring Loom question ??
Post by: cb750stu on July 08, 2013, 08:40:03 PM

Really ??
Any suggestions on what i should go for ??

Not much of a electrical guru im afraid,

Cheers

Title: Re: Wiring Loom question ??
Post by: Bryanj on July 09, 2013, 08:27:21 AM

Not sure what the original wire cross section size is but I would at least double it for that distance, and solder any connectors

Title: Re: Wiring Loom question ??
Post by: LesterPiglet on July 09, 2013, 07:17:44 PM

You can use a smaller guage wire these days compared to what was available in the 70's. I did a bit of research last year and promptly lost all my links.  :-\

Title: Re: Wiring Loom question ??
Post by: Lobo on July 09, 2013, 11:24:06 PM

(For the 400F).... OEM Wiring is generally 30/0.2 strand PVC coloured cable. Modern vehicle wiring is thin wall 32/.2 (2mm 16.5A) strand hard PVC for better abrasion resistance, higher current rating, higher operating temperature and lighter weight (but not quite as flexible).

(the above words shamelessly copied from a very professional 400F rebuild blog)

(Me speaking...). The above 16.5A suggestion should be plenty for the typical loads on an old CB750 - assuming you're not loading it up with triple headlamps etc - 16.5A would be good for approaching 200W of power - (ie  more than your alternator output) - a single headlamp is typically 65W)

To get a working idea of wire rating simply sum the watts through your circuit, and divide by the voltage (12V) to get the current rating.... eg head + tail + stop + indicators might be 65W+5W+20W + 36W= 126Watts... /12 = just over 10Amps. (15A wiring good here)

Suggest you include a fuse, with a value (obviously) less than the wire amp rating.

And check your alternator output as I think it may be I the region of 13A (156W) - don't overload it!

http://www.autoelectricsupplies.co.uk/category/10

Cheers,
Lobo

Title: Re: Wiring Loom question ??
Post by: LesterPiglet on July 09, 2013, 11:43:08 PM

I'm useless with electrickery so I just chose a wire that had a rating a bit higher than the fuses in the bike. :)

Title: Re: Wiring Loom question ??
Post by: Green1 on July 09, 2013, 11:55:48 PM

Your not the only one Lester I managed to blow the electric meter of the wall changing the living room lights  ???
Don,t ask me what I did I still don,t know  :-[

Title: Re: Wiring Loom question ??
Post by: cb750stu on July 10, 2013, 12:00:56 AM

Cheers Folks for the answers !!!
Im not going to be running indicators or electric start so im not really doing much to the loom apart from not using a few bits and just making a few bits longer to reach under the seat,im not really looking forward to the wiring part at all im hopeless with diagrams etc i might have to get my Dad up to help hes good with that kind of stuff.

Thanks again

Stuart

PS If im not using the indicator wires etc do i just blank them off or cut them back ??

Title: Re: Wiring Loom question ??
Post by: LesterPiglet on July 10, 2013, 12:11:17 AM

I would leave them in case you change your mind in the future.

Title: Re: Wiring Loom question ??
Post by: cb750stu on July 10, 2013, 12:26:38 AM

Good point Lester ill keep them !!!