I'm just looking at the speedo drive for the 45" project bike.
Right now this bike has two speedo drive points, and a problem. The problem is that the frame, having been subjected to a lot of cosmetic work, has lost the tunnel through the frame backbone for the speedo drive.
I can see various solutions, but they all start with a 90deg adapter from the speedo. These are available from various car restoration parts suppliers. I've established that the threads on a Shovelhead are 5/8" x 18 and unsurprisingly, this seems to be a stock adapter size. So, I could drive it from the Shovelhead front wheel but this leaves a rather awkward looking cable route.
The next option is to drive from the back wheel. I already have a 2:1 reduction Shovelhead speedo, somewhere about. I don't have a 45 drive cable. Is the thread on the drive cable compatible with a Shovelhead speedo, ie 5/8" x 18? Knowing HD, it probably is but I thought I'd ask before proceeding as someone is bound to know, or have the parts to check?