I'm not sure what kart you have, but I've replaced the inner tubes and tires on those old Carters with split rims and they are a nightmare. Water gets into the wheels then rusts the inside of them along with the tubes adhering themselves to the rust. I scrape off as much rust as I can, run the wheels on my bench grinder wire wheel, spray them down with Rust Kutter then paint the insides of them. One trick to installing tubes is slightly inflate the tube, place it inside the tire with the valve in the correct position then bolt the wheel halves together making sure you don't pinch a tube.
Sanco's Rust Kutter will stop the oxidation process to prevent rust from starting or control an already rusted area.
www.sancoind.com