Usually the cause is a lack of lube in the cable, and you find the cable either broken or frayed or all twisted up. If the cable is okay, check the speedo gear in the tranny, then the speedo itself. If you need any parts for the speedo itself, call Jeff at Bowtie Bits, part of his business is rebuilding speedos and gauges. Be sure to lube the cable with the proper speedo cable lube.
