It's not the original color. That should be a medium blue.
Don't take this the wrong-way, but airbrushed gas tanks, or our faux tanks, are a dime-a-dozen, especially as you go back in time. While having the bike in a magazine pic is cool, it appears to be a stock bike, so that actually is to your advantage. It may be one of the lowest-mileage bikes of its type in the world! No-kidding. As such, it may have collector interest to some wealthy Japanese collector. That's something to consider. Despite its non-original color/paint, the XXX miles, and everything-else untouched is just-what such a collector wants. I have a contact who is in Japan buying vintage 1970's and 1980's Japanese bikes of renown (Z-1's, KO-model SOHC Honda 750-4's, Wes Cooley GS1000 S Suzukis, Eddie Lawson Replica KZ1000J's, Kawasaki 750 Turbos, CX500 Turbos, CX650 Turbos, etc) who may be interested in it because of its untouched condition. PM me if you are interested in investigating this more. If you are, I wouldn't touch
a thing on the bike. "Unmolested!" That's where the value is.
Continuing.
In 4 years' use, it wasn't. That's barely break-in miles, actually, you still have some to-go! All the fluids in the brakes, clutch, cooling, and engine need to-be changed, I don't think you need to-worry about the differential, other-than to ensure the level is OK. Actually, I suspect the entire f & r brakes, and the clutch hydraulics, will need a thorough cleaning and a flush. That includes the clutch slave cylinder, which requires removal of a left-rear engine side cover, to access the two screws attaching the clutch slave cylinder to the engine case.
Be very careful in attempting to-remove those screws! It will be difficult to have to deal with that if you bugger the heads.
Brake fluid probably has badly crystallized in the calipers, and the master cylinders, and maybe the clutch slave cylinder. Do the brakes even-work? I doubt it, if the bike has been dormant for nearly 25 years. Same for the hydraulic clutch, it's probably inoperable. I'd start by removing and disassembling the master cylinders, removing the oxidation/crystallization you find, and flushing the systems thoroughly, For the brakes, you may need (probably-need) to also disassemble them, removing the oxidation/crystallization you find, and flushing the systems thoroughly.
The carbs need to-be removed, disassembled, cleaned, and installed. They need to-be tuned, including synch'ing. The gas tank probably needs to be removed and thoroughly-cleaned. Cleaning the carburetors, and hooking them to a rusty, gummed-up gas tank, is a waste of money and time.
If you can do this work yourself, and you wish to keep the bike, have at-it. If you don't know how to do the work, you're probably looking at $2,000 US in parts and labor for what I've described, including new tires, at a shop, where you authorize all that work, and probably have to leave a partial deposit. Those old tires are
very-dangerous for a bike with 15 RWHP, much-less one with 115 RWHP! Other than rolling it around, I wouldn't use the tires for anything under-power. You could easily dump the bike if you tried to use it! However, if you do decide to sell it, leave those rim-protectors on-there! Repeat after me: "
originality, originality."
This thread may help you to understand what is involved in what you're facing.
https://www.vmaxforum.net/threads/clutch-slave-cylinder-replacement.45011/