Steering damper question...I have owned quite a few Yamaha enduros, but only two have had a steering damper. My current '71 DT1E and a '73 AT3 that I had. Same part number. I noticed that they are also on some CT and RT models. I know the purpose of them, but what is it about these models that require dampers? Is it just poorly designed steering geometry? Were they a retrofit after they found out about the problem or did they just come with them from the factory originally? I'm just wondering what makes these models prone to steering shimmy or wobble as opposed to the other models. Thanks!

I think that I read in a post a few years ago that they are only needed if racing. So, if sticking to tarmac/dirt roads, then not really necessary.

They are not "needed".  In my opinion, it was a "feature" that was more marketing than anything else.  

Another example was most early models came with a tapped hole in the cylinder head to install an aftermarket "compression brake" which was a popular fad during the 1960's and early 1970's.  

P.S.  When I was involved in Land Speed racing, one of the tech inspectors used to be an engineer for Honda Motorcycles and he said steering dampers are a band aid and will not fix or cure steering shimmy caused by geometry or chassis loading.  They just make it "less violent" if it happens but will not stop it from happening.  I can't remember hearing of any factory Yamaha model with steering shimmy issues.