After the first run of my Kart on a very rough woodland track im glad i made up a comfy sprung seat , i guess most people use foam in there seats, but after driving my kart and finding out how you can feel every bump.
So i came across an old sofa and found it was a sprung sofa, so not beeing one to turn things away i took the sofa broke it down and used the wood to make up a seat base then took the springs and cut them to size and mounted to the frame, Then took some of the foam and fabric to cover the springs , Its so much better than a lump of foam, i just need to find some old leather to cover the seat..