Speedometer gearbox

During a good 250km Labour Day run, my speedo started waving around eratically and finally gave it up. I have a new cable speedo cable on it. It appears the tang that sticks out of the speedo gearbox body has broken off. The marks on the brass ring were caused by my needlenose vise grips as the cable end is now stuck on the threaded part (of course) and it just spins. Not sure if thats the problem as I haven't been able to get the cable off yet. I didn't reef it on there either...

[ATTACH=full]87967[/ATTACH] [url=ht.../52577093@N03/7940828704/]Speedometer Gearbox by niagaraz, on Flickr[/url]

I have a spare one but the internals are pooched but the casing looks good.

[ATTACH=full]87968[/ATTACH] [url=ht...093@N03/7940830288/]Spare Speedometer Gearbox by niagaraz, on Flickr[/url]

Has anyone rebuilt one of these before? Any tips on disassembling etc. I was thinking of using the old casing and the internals between the two. Hopefully there are enought good parts between them. I looked up some prices and these things are dear.

Might be your speedo rather than the drive. Symptoms sound familiar to several Smiths and Veglia speedo and tach failures I have seen on my bikes. Bushing separating the spinning cable from the guts of the instrument gets worn and instrument reads too high then eventually craps out. I recommend Palo Alto Speedo for repair.

If the problem can be isolated to the drive, replace with a genuine NOS or good used Smiths item if possible. The Indian repros are junk.

I'll be testing the speedometer, cable and speedo gearbox. The cable has about 1000 miles on it. I have a spare Veglia speedometer and a Smiths tach that need repair. The bike has a hybrid on it now Smiths speedo and Veglia tach. I've thinking of getting the Veglia speedo repaired to take advantage of the trip odometer. The bike's running great right now and I don't want to take it apart. Winter project or until something else acts up.