The bike use to be mine Michael. It was a Y1. Some parts were missing and some were not LTD. I sold the bike to a mutual friend called Hoggy and he converted it to a Flat Tracker. I know he fitted a B1 Engine and from talking to him he fitted B1 electrics. As you can see he did move some parts around bur in principal it should electrically be wired and work as a B1.
The bike in post 1 on this link is Beefs Twin
It is a lovely bike and I would love to get it back but I fear Beef will want far more than I can afford plus I would rather get it working and have him a happy twin owner. The more twin owners the merrier