Sponsorship for motorcycle racing

Hey could anyone give me some suggestions on how to write a sponsorship letter to a corporation or some small soleproprietorships/partnerships? I am 20 years old and need sponsorship for my dream to become a professional motorcycle racer. I was recently provided with sponsorship by Ducati this summer to get my license but now I have to raise $7,000 to afford the rest of my expenses for next summer. :-0 Any suggestions on the format I could use? I have asked for sponsorship before, I am the president of the business club at my college... but I have never asked for myself.. personally. It's easy to say "can you help with my club, here is our mission statement, and a tax exempt form" but this... I dont know why but I have been having trouble trying to get the right words out. Any help would be greatly appreciated!!!!!!!!!!

Thanks,

Crystal