I’m trying to sort out my tach and speedo issues. Both are failed, I’ve taken the cables apart, cleaned, lubed and verified “continuity” on both. The ends appear fairly square and in decent shape for being original. 
Question, how do these normally fail? I can push the tach cable forward and it reads correct, I don’t want to start ordering parts until I get some input.
 

Tach, speedo or both to test with a drill?

You can test both with a drill.
Drill needs to be in reverse.

+1 to testing with a drill in reverse. I've got an old cable that I use and it's a two minute job.

Update: I tested both speedo and tach with a drill. The speedo works but the tach is all over the place. Maybe the gear (for speedo)is bad at the front wheel? I’m guessing the tach is bad, any recommendations for an overhaul shop?

DEET, here on this forum.

Thanks!

There's a stamped washer in front hub with tabs on it that's part of the speedo drive... not uncommon for a ham-fisted mechanic to jam the wheel into place without the tabs in the gaps between the drive lugs that spin the washer... rendering the drive inoperative.

Not that I've ever done that once or twice! 

Easy fix, straighten tabs or replace washer.

I’ll check that out, thanks! Most people I knew used these off road and weren’t too concerned over turn signals, speedos, etc back in the day.

Arrows point to tabs on washer inside brake plate speedo drive. They engage small lugs on wheel hub. There's about 350 degrees of free space where brake plate drops right in to hub and tabs miss the lugs... and about 10 degrees of rotation where lugs end up on top of tabs during assembly and they get bent down. No more drive.

It seems like it would be hard to mess up, but I've seen it quite a few times.

Tabbed washer has hole with two flat spot that fits over and turns the speedo gear, so if tabs are bent down or washer is bent/damaged so it doesn't spin gear, no speedo.