Earth wire electric bods need your advice.

[TheSmiler]

After a problem on the bike I'm needing a new earth wire. Now I'm wondering what is the best type of wire to use and ampage. Never liked or got along with electrics hence the question.
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CB125>CG125>GN125>ER5>K100RS>R1100RS>K100RS
A2 completed 23/07/15 Ready for the Golden Crisp Packet

[c_dug]

There isn't really an earth wire as such on a bike, what exactly do you need?
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I am a bellend, I am a man of constant sorrow, I am a gummy bear, I am a rock.

[stinkwheel]

The thicker, the better.

If the starter solenoid connects directly to the battery negative with a big fat wire, the frame earth needs to carry up to 30A (usualy size of the main fuse). I'd go with at least 4mm^2 multicore cable.

If the only connection to the battery negative is the frame earth, it needs to carry starter motor current. So it needs to be about as thick as a jump lead. You'd want to buy a pre-made earth strap because conventional crimps etc wont be up to the task. So in the region of 15 to 20mm^2. Especially if it's for your brick engine BMW because they'll draw some serious cranking amps.

It is not wrong to use a thick earth strap in either case. Loads of them on ebay, all different sizes. This is just a random example: https://www.ebay.co.uk/itm/9-Classic-Car-Earth-Strap-Battery-Lead-Cable-Flexible-Tinned-Copper-Braid/121930637020?epid=651851216&hash=item1c63a1dedc:g:EQwAAOSwv-NWaFQw
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[TheSmiler]

The only connection to the battery is the negative from the frame its about 850mm in length worth of cable. I know now for a fact that if a certain problem happens that you can disconnect the earth cable save it going fully on fire.

You can see how lucky I was on the old standard earth cable. I'll have a look on ebay see if i can find an earth strap that meets my requirements.
____________________
CB125>CG125>GN125>ER5>K100RS>R1100RS>K100RS
A2 completed 23/07/15 Ready for the Golden Crisp Packet