Alright then...
I just looked into the file, but having some difficulties, I wasn't able to understand everything.
Problem 1: Character Size
It looks that your character is too big for the kart.
(Problem 2: Texturing
Material View looks almost the way it should, but I'm not able to see textures with "Textured solid". Also Textured view doesn't display the textures completely.)SOLVED
Problem 3: Animation
I don't know if it was planned, but the characters tail doesn't have enough bones to create a proper speed-weighted animation.
I didn't have the time to grapple with it more detailed, so it might be that some of my problems are quite easy to solve.