kenda = super cheap Taiwanese tires = junk. A $59 tire is $59 for a reason. Spend the extra $30 for a quality tire.
the Bridgestone S11 is definetly a better quality tire. It is not even listed on the Bridgestone website anymore, so I am assuming it is very old and discontinued.
if the tires are over 5 years, I personally would not ride on them. Fresh rubber does a world of good for a motorcycle's handling and braking characteristics.
modern tires, fresh from the oven, have better rubber compounds and carcass construction and tread design than tires of yesteryear, and will offer better braking grip, and cornering, as well as steering feel.
far better than anything that was available back in 1983 (back when the original tires were new), and a shit ton better than old, possibly cracked and hardened tires.
You should be able to swing a set of fresh name brand buns for about $200-250 for the pair
I personally love Michelin tires, and the Pilot Activ would be a great choice for your bike.
You could also possibly move up one tire size front and rear, assuming you have the room inside the front fender, and also where the shaft drive is closest to the rear tire.
your stock tire sizes are 100/90-18 front and 120/80-18 rear.
You could possibly go with a 110/90-18 front and 130/80-18 rear.
http://m.michelinmotorcycle.com/tires/street/pilot-activ.html
The Dunlop GT501 is also a good choice, though they are only available in the stock sizes:
http://www.dunlopmotorcycle.com/tire-catalog/road/street/gt501/
And in Bridgestone, the BT45 is also an excellent choice:
http://www.bridgestone.com/products/motorcycle_tires/products/battlax/bt45.html