Rewiring bike to 12v

Information relating to the Matchless G11 or AJS Model 30 600cc twin
Posts: 532
Joined: Sat Jan 01, 2000 12:00 am

Rewiring bike to 12v

Postby moley » Fri Sep 21, 2018 6:54 pm

Hi All

My father wants me to reword his bike which is a g11 , it has alternator but magneto for his ignition.

I need to know what wire to buy I normally buy wire for 6v and I use 14/0.30 8.75 amp wire

But I don’t know what wire I should use for 12 volts

Any suggestions ?


Posts: 1403
Joined: Thu Jul 04, 2002 12:00 am

Re: Rewiring bike to 12v

Postby Groily » Fri Sep 21, 2018 10:31 pm

Here's one view for starters Andy . . .
14AWG is usually reckoned to be good for 12v systems, with maybe lighter 16AWG for things like side lights. The heavier gauge for the battery cabling to switch and ammeter, for sure. I think the wire gauge sizing translates into 28/0.30mm and 32/0.20mm (it does - I just checked in James Smith's Big Book on classic m/cycle 'lectrics).
(I think for 6v you might have been under-strength actually. It's not just about current capacity, but also about voltage drop along the way, which is more of a worry at 6v.)
And not forgetting fuses . . . I tend to use 10A for the main fuse on 12v systems. I also always make sure the brake light is in a fused circuit, as they're a common point of failure, what with wires rubbing under mudguards etc.

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