Anyone know how to get a gear cable into this (from the narrow end), how do they get them on in the first place?

http://i58.tinypic.com/2vnlw92.jpg%5B/img%5D

Mine have always gone the other way ie.Out through the narrow bit with the rubber johnny/balloon then fitted over.

I’d imagine a thin straw(like what comes with GT85) pushed through the balloon bit then push the cable inner into the straw, then pull the whole lot back through.

The cable inner should push straight into the sealed end ferrule if its not frayed(cable inner that is).

I have one like that on my bike (jag wire cables) and I just put a bit of grease on the end of the inner cable and slid it on. If you rotate the cable the same way as it is braided that helps, as does the cable being new or cut with very sharp cutters.