Electrics cable advise please....

[smifffy111]

Hi,  My fathers triumph speed twin circa 1950 is in need of a new wiring loom and I was hoping for some advise on which cable size/specification to use.
Any information would be much appreciated,
Thanks.

[R]

Are you looking to buy one off the shelf, or make your own ?

Modern harnesses seem to use much thinner wire than of old. Much thinner.
Study whats presently in it and duplicate it seems the best bet.
Unless someone is planning extensive night time rides, it probably makes little difference though.

I bought some extra heavy auto wire to run to headlamp and return, and for the horn from the battery, since those are the only heavy current users.  Modern bikes use relays to get better headlamp power, may be worth trying if night time riding is intended ? Since old time handlebar switches aren't really intended for lots of amps, can lose a bit along the way.

Opethiselps.

[Rex]

Try Vehicle Wiring Supplies. The catalogue used to list different sizes of cable with ratings and typical uses, and sold by the metre too.

[johnnyboy-wonder57]

Hi,
Use serviceable stuff to take the weather and vibration, my 20 year old BMW has a pathetically inadequate wiring loom in wire thickness, as it uses relays to handle the loads on the system, but because wiring looms that are especially thin, age  and get less supple as time goes on they start to break & you get problems.  Use an adequate durable  thickness of wire, measured in amps because, electricity flows like water down a pipe so make sure it has the right carrying capacity,  in amps, then if it looks to thin go for a slightly thicker wire and then importantly put a fuse in the live feed wire from the battery, 30 amps,  so no possible damage can take place,  if anything goes wrong, the fuse will blow & no damage will be done to the machine!

On old machines you have only the charging system, ignition wiring and the lighting to worry about,  and respective switches, rectifier in a heat sink e.t.c, if you build your own loom, you get work through each one individually from your different respective  live feeds branching off from the battery and earth appropriately on the main frame in metal to metal contact points.  Update your system with a centralised accessible fusebox for ease of maintenance.

Is it 6 volt?  If so can it be converted to 12 volts,  then do it , if the cost isn't prohibitive, can the headlamp be upgraded for safety reasons?

I have a wiring diagram for a simple restoration from a custom site, but its useful for giving you an overall idea of how to wire a bike up!  My email is in the Ariel Square 4 enquiry.


Cheers


John


JBW

[wetdog]

get a old washing machine ( tip ) plenty of wire and will do no problem with lots of nice connections , my old k100 bm also has poor wireing  but i am slowly replacing as it fails 130,000 miles and still going strong , im sorry to say the most relyable bike ive ever owened and it lives out side my front door

[johnnyboy-wonder57]

Good tip, I have just stripped all the wire out of an old washer, of note in diagram a horn would need to be added via the ignition switch live feed, with wire of ample thickness to carry the load required. Obviously meters and gauges could be factored in too.


Cheers

John

JBW

[smifffy111]

Thankyou all for your comments its much appreciated, 

[Rex]

If you're going down the used route, why not get a bike loom from a breaker? They normally go in the skip with the frames.
A decent length of cable in a variety of sizes and colours.

[twolitre]

Presumably your Speed. Twin is 6 volts.
Remember that most. if not all, modern bikes are 12 volts and hence, at twice the voltage there will be only half the Amperage flowing through the wires to similar components.
Your 6 Volt system wiring therefore needs to be twice as heavy as 12 Volt.
As a ROUGH guide each strand of .3mm wire will carry about half an Amp. Hence cable marked, for example 14/0.3 will carry 7 Amps. Sizes seem to have changed lately, but the first number is the number of strands and the second the strand diameter. Do not use strands thicker than 0.3mm (0.012in) or vibration fracture risk increases.
Choose a different colour for each circuit or fault finding later can become a nightmare.
Jim.

[twolitre]

Looking back at your wiring diagram, I see that it is for an alternator bike, WERE Triumphs the age of yours alternator bikes? I know they were in the mid fifties, but earlier?
Jim.