Hi I have a 1942 BSA M20 and I am trying to buy a speedo cable of off Draganfly but the year for my bike listed says 24.5 but below says a year that is not mine but says for girder model which is 26.75. Does anyone know the appropriate length?
It's going to depend on whether you have the long or the short forks, whether you have the early speedo drive on the brake plate or the more common separate unit on the left and whether you have a centrally mounted speedo or the later bracket offset to the left.
The best bet is to mount speedo and drive and then take a length of stiffish electrical cable that will follow a speedo cable-like bend. Route it as you would the cable and measure from flange to flange. That way, you'll be sure that it will fit your particular combination of parts.
On girder forks, there is obviously no need to take account of suspension travel so just concentrate on a smooth line with no stress in the cable outer.
