Dave,
That’s a tough one. There are very few spectators at a kart race. Not to mention limited television or other media coverage. Mostly other racers and families in the stands. So sponsor exposure and their return is minimal. Your best bet is to talk to people you do biz with or vendors you use to get a little here and there. Some of the racers who own a business support their own efforts.
Once you are consistently running up front and maybe a have Championship or two under your belt, you have a little more leverage to raise money.
We’ve found it a little difficult to get a significant amount of money from any one sponsor. We have been able to get a little here and there. Which may be your best approach.
Rick