Speedometer dissection, troubleshooting

When I bought my '86 VFR 700 a couple of months ago, the odometer wasn't working, but the speedometer and trip meter worked fine. Riding home one day, the speedometer went out, so I started troubleshooting the system.
1) Bought a used speedometer off ebay. By removing the 90 degree, gear turn assembly on the back of the speedometer, I could chuck the main shaft in to my drill driver. With that I could verify the new unit worked: odometer, speedometer, and trip meter. BTW, my drill driver goes 15 mph. ;-)
2) Assuming the cable was bad, I found a flat head bit to put in to a drill driver to turn the speedometer cable, connected to the replacement speedometer. Cable was fine.
3) Using a sharpie, I marked the front wheel speedometer outer housing, and the blade type drive coming off of the gear to the front wheel. Then I rolled forward a foot, then ten feet. My thought was that it's possible one check point could have rotated to exactly the same position as where I started from. Unlikely that would happen twice.

Used speedometer gear should arrive today from ebay. While I'm this deep, Replacing the speedometer cable with new since I broke the plastic clip where it attaches to the front wheel, as I was focused on checking the drive gear.

 

The latest culprit for the speedometer unit not working, was the gear connected to the front wheel. $25 shipped for a used unit off of eBay. With a little juggling, after I pulled the axle most of the way out, I could swap in the replacement unit, without having to take the wheel all of the way off.
While I was this deep in to it, I put a new speedometer cable in too. I think it was $20 shipped off eBay.