If you had no caster at all, just kingpin inclination, when you turn the wheel, left or right, both wheels go equally. That action raises the front end a small amount. If you had no kingpin inclination, just caster, when you turn left or right, the inside will goes down and the outside will goes up. It also raises the front end. A car doesn't need caster, it uses kingpin inclination, in fact there was a time when they put in negative caster to make it easier to stear. A kart uses a solid rear axle, versus a differential like cars have, so unlike a car, a kart needs to get the weight off the inside rear wheel in order for it to turn. Because kingpin inclination causes both tires to go down the same amount when turning left and/or right, if you didn't have caster, you would go straight at the end of the straightaways. My personal experience, with my "homemade" Mako shark, which had no kingpin inclination, was that the kart handle just fine, in fact, better than most.
Now I've been told that, because Sprint karts are different from LTO karts, this innovation does not apply, but for the life of me, I can't figure why!
I'm old, and my shoes are too tight, and my feet hurt, and I like it. (Dana Carvey) I love that guy.