I worked at a Triumph, BSA, Norton shop from '70-'75 and the new bikes overall weren't really that bad. I didn't car for the '71 frame, it was too tall. But we didn't have that many warranty problems. However, owning one will remind you of what the Good Old Days were really like! The old English bikes were just like an iron barrel RE, they require a lot of TLC and maintenance; valve adjustments, carb cleaning and adjustments, timing adjustments, and much more frequent overhaul and top end jobs. as was mentioned, an electronic ignition system is a must if you want to the reduce maintenance time on the bike. Not that they're hard to start, but the system will keep it that way.
My favorite Triumph 650s were the '68-'70 single carb models. My favorite Triumphs, though, were the '68-'74 single carb 500s.They were a lot lighter and smoother than the 650s. Far superior machine in everything but outright speed. They were somewhat faster than an Enfield with a top speed in the mid '90s, but if you're going to buy a Brit bike you not buying to go fast! I used to race scrambles and more often than not I beat the 650s with pretty good regularity. It was lighter, handled better and got better traction in the dirt and the wheel spinning 650s.
Bare