i just got a 77 honda ct 125 endero bike and even though it dosent have much to do with a cbr 250, they are both light weight screamers. i can not reack 10k rpms (like i said endero bike) but for a 13 year old im prety sattisfyed with the revvs, and hope one day to put a 1.3 liter rx8 motor in a suzuki hayabusa (1.3 liter) then with some cpu adjustment have a 15k rev limiter with <200 hp. like that will ever happen

car engines are alot bigger then bike engines, so it will be very heavy, and hard to do. your easier just sticking a powercommander and a zaust on a busa for good power.