If it was within a couple hundred miles of me, I'd probably get it - after getting the price down to a grand.
Twenty years ago I got an R90 that sat out for five years in Portland Oregon. I thought it was only good for parts, but every step of the way things cleaned up, ran super, polished up and is still running today. It did take a bit of work cleaning and polishing but was well worth it. It did require a few seals, though - like the trans output seal, new alternator brushes (the old ones were deteriorating and coming apart), tires, battery and forget what else.
Frankly, R65 cylinders come cheap (though I doubt that's what's wrong), and if you can do your own work, this bike would be a great opportunity to get to know your bike and have a good runner (and probably looking good too) fairly inexpensively. But if you don't do your own work, the labor and cost of new parts would put it over the top.
I'd take the chance on it.