Need help with a speed warning speedo

[StingRay]

I have a speed warning tach cluster I picked up for a very good price. The cable turns but there is no needle movement. Upon disasembly I find that the adjusting cable fits into a sleeve with a small blue gear on the end. That gear is there and is fine. There is one small rusty brown gear being driven by the blue gear. It's a long way between that brown gear and the brass gear on the speed warning needle with nothing in between. I know something is missing but I don't know what. Are parts available to fix the speed warning speedo head and does anybody have a pic of a working head from the back side so that I can at least see what I might be missing?