Ok....
WHY would someone buy an old bike "still in the box" and then ride it?
Sorta missing the point... no? If you want to ride a vintage CBx, buy one and ride it, for half the asking price... AND you're not starting the only unstarted CBx in the world?
They're only new ONCE, and there is no great lack of CBx's.
IF you were to buy a 40 year old "new" bike in a box, it would require a TON of maintenance IF you wanted to act like a NEW 40 year old bike.
You would need to replace pretty well anything rubber: brake lines, carb boots, engine and suspension seals, tubes and tires, even handle grips (even if the thing was stored in a climate controlled dark environment, unless you figured out how to keep these parts from oxidizing for 40 years)
You will need to replace the piston rings, at least. Rings are made from "spring" steel and have a "memory" for shape. If you compress rings into one position for any length of time, they stay that shape. 40 year old rings that haven't moved for 40 years aren't long for this world.
You will need to replace all the bearings on the bike. Bearings are designed to move. Bearings are made of parts of dis-similar metals. When you put dis-similar metals together, you get galvanic corrosion.40 year old bearings that haven't moved for 40 years aren't long for this world.
Ditto valve springs
You'll want to lap the valves... blah blah... galvanic corrosion.
ANY factory installed lubricant has succumbed to gravity long, long ago
... the paint should be good to go though... but be sure to check what the INSIDE of the tank for rust.
OOPS spoke too soon
https://cdn.bringatrailer.com/wp-co...upersport_158836470031797aIMG_0979-scaled.jpg
Here's more
Original-Owner 1982 Honda CBX Supersport in Factory Crate I think it's the same bike
CBx's didn't handle particularity BAD, for their time. They were a handful because of their size (they're about a yard wide at the crankshaft). They were much like their CB/F brethren, better than the Kawi's, not as good as the Suzukis. They had spindly forks and lousy brakes... but so did everyone else, and to Honda's credit they did try to fix both(compare the Jay Leno bike's front end to the earlier silver bike).