The 85 K bikes have some differences than later years.
1)The rear gas tank mount, and electrical connections to it were modified due to to cracking, so check that out.
2) brake line goes through the steering stem, can rattle if loose.
3) Water pump impeller used a nut to secure it instead of a bolt; the nut has a tendency to corrode and fall off, requiring a new shaft. So its cheaper to replace the water pump than rebuild it in this case.
4) different camshafts that are smoother, and a little more power than later Ks.
5) Seat is different than later models and not interchangeable.
Its a great bike that will run forever; if it hasn't been done you'll need to repack the steering head bearings as the old grease has hardened.