Water pumps aren't rebuildable. They're also expensive. And the single most common problem I've seen is that the inner oil seal works loose and the pump leaks oil out the weephole. As long as there's no radial or axial play in the shaft, and it's not leaking water, the pump is completely repairable.
first, clean the pump well. Brakeclean is a favorite. Remove the inner seal, the circlip, and the seal for the inner bearing. a small pick works well for removing the seal. Pack the bearing with some wheel bearing grease, reinstall the bearing seal and circlip. Now clean all the grease from the inner bore. A couple Qtips and some brakeclean does a good job. Install a new kawasaki seal # 92049-1416 with some locktite wiped around it's outer diameter to help it stay intact. Be sure you install it so that you're looking at the inner lip of the seal when you're done (flat side toward bearing). Tap it down squarely until it's fully seated. Let the locktite set up, then reinstall the pump. Easy to do, and will save about 175.00 on a new pump - HTH, Steve