I couldn't believe my luck. I was GIVEN an 85 CB700SC nitehawk about 6 months ago. It has 72K miles on it, and had been sitting for 6 mos. I flushed the carbs, charged the battery and it runs great. It's very fast.
There isn't much to tune up on these things; Hydraulic valves, modern ignition, and shaft drive don't leave much for tuneup besides oil/filter change, and air filter.
Mine had a snapped valve cover bolt that the PO drove with for a very long time. He stopped riding it cause he got tired of changing the oil in his pant legs! There was oil everywhere and quite a mess. I extracted the bolt and fixed the cover leak
I went for my first ride a couple weeks ago in the twisties by the Calaveras reservoir, and this is a very nice bike. It's got a 10,700 red line and snaps the head back during windup between 7 and 8 K like some sort of boost comes in. Very strong and, for me, a bit scary. The brakes are very effective, though..
After driving this bike I can see why the SOHC4 became less popular.
It has a bunch of suspension and shock adjustments front and rear that I haven't figured out yet, all factory.
I'm still trying to get used to the quick steering, though. It needs quite a bit of counter steer in turns and going in a straight line is difficult as it tends to wander in the lane on freeways if you don't pay strict attention. I'm hoping that the worn center of both front and rear tires will help with driveability.
It also came with Riffle fairing that was painted too horribly to put up with. I have it stripped and am waiting for the weather to warm up for painting. That's why it is missing its stock smaller windsheild.
Probably the biggest problem it will have is parts availability. The used market appears very very small, and I don't know how big an inventory Honda still has for spares. Though, they did have the turn signal mounts it needed.
But, if you don't smash it, it seems a very low maintenance bike, indeed.
Don't let people tell you it's just bored out 650. The 700SC is it's own design. I don't think many, if any, parts are interchangeable.