The first bike that I bought when I began riding in 1992 was a 1985 CB 700 Nighthawk S. I bought it shortly before starting the MSF course. I highly recommend taking the MSF course before riding a motorcycle on the street. What they teach you will save your ass several times over.
The CB 700 Nighthawk S is a typical Honda Motorcycle in that it has a transverse four cylinder, DOHC 16 valve engine. Early Honda's had 8 valves (two per cylinder). Later bikes (post 70s for the most part) all have 4 valves per cylinder. The Transmission is a 6 speed box. The bike has a tubular steel frame with a box section steel back spine that runs from the steering head to the area just above the carbs. Surprisingly rigid for a mid 80's standard.
The 700 S makes a great bike for around town riding as it has a shaft Drive and a minimal fairing. Not much in the It also has Hydraulic tappets that self adjust. That means no valve clearance checks. A wide comfortable seat is supportive enough for moderate rides of 2-3 hours with out too much discomfort. (Corbin makes a replacement saddle.)
The addition off a 16 inch wheel up front and a wide tall bars means cranking the bike around in turns is easily accomplished. The high center of gravity off sets the lower stability of the 16" wheel up front.
If buying one used watch out for the starter and that the tranny hasn't been abused. The shift drums are prone to fracturing at the junction of the 2nd gear detent. This creates a false neutral and eventually disables 2nd gear. Other than that, I'd say that these bikes are bullet proof.
The second bike that I own is a 1972 750 Four K2 that I bought from a friend. I like this bike a lot as it is very significant in the history of Honda Motorcycles.
In 1969 Honda came out with the CB 750 K0. This bike blew away the press because it was very fast and for all practical purposes it was the final nail in the coffin of many Euro bike manufacturers.
The K2 ('72) model that I own differs little from the '69 model. Mainly a difference of sprocket sizes (18 instead of 17 teeth), less clutch tension, and a few other minor changes that made the later models more sedate.
The 750 Four is similar the modern Honda fours. It is a 750 cc SOHC 8 valve transverse four. A 5 speed gear box and chain drive compliment the early sporting style of this bike. The frame is a welded steel tube job that is pretty flexible by modern standards but better than average for its age. In the 70's it wasn't state of the art, but it did its job well. The largish wheels (18" front and 17" rear) help stability considerably at high speeds.
The valves are adjusted by screw type adjusters. This is an easy job as there are little ports to access each adjuster. One can even perform this in the field. I performed this adjustment at the Assault on Deals Gap one year. Just be sure and have some spare adjuster covers. They are prone to fatigue around the threads.
I know of few problems with these bikes that require major service. The main issue that I am familiar with is the head gaskets can blow. My bike has a slight leak. This has yet to be a problem. The big problem with this is that if it does blow big time, engine removal is required to pull the cylinder head. Not difficult, just time consuming. Be sure to have a hand when you go to pull the mill.