[bone450]

For rear tires you want to get 18 inch tires. They give you a lower center of gravity. Also if you are just racing mx, depending on the track most people don't run a rear skidplate, that way you don't get hung up as much on the ruts in the corners. Like some said before don't worry to much about the motor right away, I sure you can scare yourself enough with just pipes. :p I know I did.