If it has the original Bridgestone tires, the recommendation is 28/28 (up to 32 rear for heavier loads). It seems the general thought is that Kawasaki pressure recommendations are a tad low. Too low pressure leads to cupping and poor tire life. I run 33 psi on the front / 35 psi on the rear.
Try various pressure combinations to see what feels best (within reason) to you.
Montani Semper Liberi
2003 Vulcan® 800 Classic - Pearl Mystic Black
National Cycle Custom Heavy-Duty Windshield
Mustang Two-Piece Wide Vintage Touring Saddle
Volar SissyBar/Backrest - K&N Air Filter
Viking Quarter Circle SaddleBags & SissyBar Bag
Scootworks Sprockets (18/40 - 2.222:1 ratio)
Baron 3" Bullet Tachometer - Engine Guard (black gloss finish)
Michelin COMMANDER II front 130/90-16 73H, rear 140/90-16 77H
EK X-Ring Chain, Deer Warning Whistles & BackOFF® Brake Module