hello I bought a bis recently and the speedo wasn't working...at the weekend I finally got around to fitting a new speedo cable...screwed it into the speedo and turned it to check it worked and it does...came to screwing it into the back of the gearbox and it appears as though some of the old cable has snapped off inside the receptor for it on the back end of the gearbox as I couldn't get the new cable in far enough for me to be able to screw the retaining washer on. can I buy this part on its own or does it only come as part of a gearbox??? and where can I get hold of a new 1? thanks