if you already have a 4 mil crank, send the jugs to get ported, get new pipes, maybe shearer or cpi, head with PROPER domes. that would prolly eat up a grand, give or take. with the rest, put some attention into the trans, cut trans or full override depending on what you are doing with your bike. if you still have some money, give some love to your suspension. depending on what your intentions with your bike are, i would consider suspension before i would motor work. a 50 hp bike with $2000 suspension is waaaay more fun to ride than a stock suspension bike with 65hp, just my opinion of course.