[Andrew Rowe]

I have done many a conversion of generators from 6v to 12 volt. We use the original body and armature of the 6 volt and get a 12volt gen, something like a Lucas C45, 12volt ( The 45 means 4.5" in dia. ) so find one that is roughly the same diameter as your original that you want to keep. Take the field coils from this gen and put them into the 6volt, and you should be able to achieve 12volts. You can normally find these old 12 v Lucas gens. for $5
Find a gen. that matches your dia. , screw pattern for fixing the fields, normally just two field coils, and put them in the correct way. You can test your new rebuild by "motoring up" , but also test on a testbed to make sure you achieving the desired output , Cheers Andrew.