A few years ago, I saw this on craigslist near my residence. It was offered with a 5 hp Briggs flattie as part of the deal. It was also cheap......When I got it home I discovered that it was an old Simplex Challenger race kart from about 1961-64. The rear of the frame has been changed, but otherwise it is all there. So I disassembled it and had it media blasted and powdercoated its original black. Then new upholstery was made from the old stuff used as a template. The 5 hp Briggs went on my Ruttman Toad minibike. So I put on a BSP clone and it runs great. The original 80 tooth rear sprocket is designed to bolt on the left rear wheel and also utilize a 5" brake drum. Then both wheels go onto a splined rear axle so it has a live axle setup. Well, I wanted a 60 tooth rear, so my brother Frank fabbed me a 5" steel drum with a 60t chainring. This particular red painted steel BMI wheelset is used with the 60t sprocket. The original 80t will be used with the original aluminum wheels sometime after the kart gets some track time.
A previous owner did some major frame damage and did a really poor job of repairing the damage. I fixed and modified it, and the stretched the frame so I could fit.