This dirty old 1988 Kawasaki en450 also known as a 454 ltd and the same engine on early Ninja 500s was in need of a carburetor cleaning. After removing the carbs from the bike, about an hour job, the bowels and top bladder were removed, the needle jets rubber cone were wrapped and required replacing. While Kawasaki's don't hold their resale value as much as other brands, this motorcycle when in use as a daily rider never had any problems, always started, always got to point-to-point B. But after sitting in a garage after several seasons without a quality detail, and bad gas in the tank, the same old story of gum in the carbs shows itself.
The dual carburetor setup requires two carb rebuild kits, prices range from 35 to 50 usd per kit depending on where you order them from, try a local motorcycle shop.