sponsoring a kart for a business not linked to kart racing... is basically a gift... if you believe you can drive business to them by putting their name on the side of your kart... I'd be interested in how... I do think there are ways you might get a business involved that might make you a few dollars.... but for the most part if you have a business giving you $$ for your kart racing you have a bennifactor not a sponsor 99% of the time an employer or family friend...
What can you offer a business? that will increase their business that will give them a ROI (return on investment) if they buy a $100 sponsorship on your kart... they need to generate $500 in sales to break even... if you can show them they will increase sales by $1000 then that is a 100% ROI, Not saying it can't be done... people deal with people they like if you present it well are passionate about it and stay in contact you might very well build a relationship that could last for years. ask for a little and deliver a lot is always good