Tires
Canon,
Maybe I can help you out on your tire situation. If you have stock wheels, you probably do have a 21" front and an 18" rear. I do know that Kawasaki offered a 19" rear wheel as an option at some point in time. The tire sizes are just like car tires-- Tricky. The first number is the sectional width in millimeters. The number after the slash is the aspect ratio. This is the tricky part. For the most part, it is the percentage of the width that the sidewall heigth is, but not always. That is why it is so tricky. For example, you have an 80/100-21 tire. This means that the sectional width of the tire is 80mm wide, the sidewall is 100% of the width tall (80mm), an it fits on a 21" wheel. If I am not mistaken, your bike's stock sizes are 80/100-21 fronts and 100/100-18 rears, like most KDXs. I don't know about the caliper, sorry. But, I hope that this helped you more than it confused you.
Collin