My mate has a VN berlina, and I'm trying to hook up his tacho for him. I don't really know much about VN's, and he threw away the instructions, so I'm kinda stuck. I can hook up the + and earth wires, but I'm not so sure about the other wire, which should be going to the negative side of the coil. Can anybody tell me where I should be hooking it up to?

the negative side of the coil would be a good start the 4th wire is that off illumination if u dont know its purpose. how u fit it ok

Ok, I'm not stupid. What I was asking is what colour is the wire and where is the easiest place to connect to it.