I swapped out the non functioning tach from my 73 dt3 with one I got on ebay...it was for an AT1. Same fit, lighting almost the same except it has the brights indicator.  Functions but seems like it reads quite high.  Am I missing something,  perhaps they are not as interchangeable as it may seem. Maybe it just needs to be calibrated.   Insights?
otherwise all is well. Thanks to KDI, Deet, a fellow named buzzard over in Michigan, my local mechanic,, and probably a lot of other people I can't remember it is a super nice ride again.

This is a non essential item for my enjoyment at the moment. Perhaps next winter I'll send gauges in for new faceplates and a checkup 

I'm not sure why you'd buy a tach with the wrong red line? "Am I missing something?".  Yeah it's not made for your bike LOL.  Seems dangerous (higher red line) and obviously wrong for those that follow these old bikes. DEET on this site rebuilds them and puts new faces on them. He would know if the internals are the same as what you need.

All the Yamaha tachs of that era are calibrated the same...  by that I mean the same input rpm on the cable should result in the same rpm reading on the tach.

That doesn't mean yours isn't off and, yes, it would be prudent to observe the lower redline for your model.

Yes for sure.  I don't let er rip by any means.  I'm an old fart who might be going 40 down a paved County road or 25 in town...  that's exactly the info I was looking for.   Thanks!! 

Wind certainly has an influence in tach readings, and speedo too but more so the tach. Mine starts waving at me anything over 40 MPH!

Frequent cable lubrication reduces waving.  However I have not found a lubricant that keeps it from waving for longer than a month or so.

What's a good lubricant?
it seems like it registers higher.than it should...