While I'm not completely familiar with the BSA entry, I'm quite familiar with the Royal Enfields. Yes, Harley Dealers have them, or most do. The Indian (made in India) Royal Enfield has had some growing pains over the years, starting with just trying to build a decent set of engine castings that would hold up. Until about 10 years ago, it was still a problem! But, the success of the Royal Enfields re-entry into the world market allowed them to invest in some better technology, both from a metallurgical perspective, as well as updated electronics and fuel delivery systems. Today's EFI Enfields are actually pretty good motorcycles!! But, back to Yamaha:
While the traditional 'XS-650' (incl TS and other) motor was never produced in an EFI version, Yamaha has ALL the technology needed to adapt a single or multi-port injection system on to this vertical twin platform...... and make it start and run like it NEVER did! Granted, a LOT of tweaking and/or investing in alternate carbs and/or ignition systems can overcome a lot of the woes from 'stock' configuration, but lets face it: EFI Rocks!! I'm 72, been doing this crap with carbs of all types since I was 12 (yea...that's 50 years of it!!). I'll take EFI any day, even though I still think there's a place for a carb motor (on a vintage show machine!!). But more than that, there have been advancements (or 'alternates') in terms of things like Hughes re-manufacturing of the crank and cam, delivering a new approach to the good old vertical twin! How does he call it?..... 'home built'??!! Think what Yamaha could do!!! And, they have the ability to manufacture this stuff in volume, build a reliable and 'high-performance' version of the 650 twin motor.... AND package it all to look aesthetically just like the original. Hey, they might even fix the electric start problems!!!.....lol
My point is this: That motorcycle hits a sweet-spot in the market that hasn't gone away! It falls into nearly EVERY category of available motorcycle at some level, being light, sporty, capable of two-up riding, reasonably powerful, and clearly (after over 50 years) reasonably reliable! Good for local transportation, or even an extended trip! Granted, it's no Harley ElectraGlide, nor is it a Ninja, or 50cc scooter. And, yea, it DOES need some effort put int 'vibration and suspension' management. Maybe a rubber mounted motor and some 'good' shocks and forks? But think of the possibilities!!: A 'sport' version, a 'touring' version, maybe even a 'trainer' version (as light and low as possible!!). I've wanted to build one with a faring, hard bags, and FishTails!!.......lol. (yea, I ride my 2020 Street Glide regularly!!). Anyway, I believe that if Yamaha 're-issued' this motorcycle with all the needed upgrades, they'd sell a million of 'em! I'd be in line today to order one!! Hell, maybe I can get Yamaha to offer me VIN #00001......lol Wishful thinking!!