I ended up getting just $2000 for my 75 CB550F from a guy in Bozeman who was very happy. It was in great shape and needed nothing to enjoy and very little to make it perfect.
I found that the carbs on the old CBs are a nightmare. At first a simple cleaning and rebuild kit did the trick but then after 6 months they seemed to constantly have additional issues. Too much flow, not enough, floats not opening, and then not shutting. I admit I'm no motorcycle mechanic either but 4 of those buggers may be great for max power per CC but terrible for day to day.
A 750F is probably worth a little more although I bet the CB400F might be the most valuable of them all. I've seen some 70's GL1000's for a good price, I wonder if they wouldn't be a better choice. like this
https://greatfalls.craigslist.org/mc...579991710.html