The first thing you need to do is to gather all the parts, as it makes it much easier to design if you can lay out all the parts where they will be on the kart and kind of 'join the dots'....
Go Kart Parts. When it comes to go kart parts and kits, BMI has it all! Here you`ll find the best prices and the largest inventory in the karting industry! We have a large selection of replacement brakes, bearings, axles, air filters, chain, hardware, clutches, engines, tires, rims, spindles, torque converters, chassis, frames, and sprockets. These Racing Kart Plans, unlike the Free Off-Road Kart Plans do not cover alternative methods of making the Kart, and assume bearings, bushings, wheels and hubs are purchased from a local engineering Suppliers. Please refer to the other sections on this Kartbuilding website for these extra details on engines, brakes, bearings, drive & transmission, wheels, steering etc.
Materials you will need: 25 or 30mm Square Steel Aluminum Sheet 1.6mm thick 19mm and 25mm Steel Tubing 25mm solid 30mm bright solid (If you want to make your rear axle) 13mm tube or pipe. lots of 6mm and 8mm nuts and bolts Parts you will need: (Screen shot are includes as the ebay links can go dead)
I recently bought a number of parts from cut price racing, they have almost everything you will need and their service was excellent .
Axel (You can find these second hand on eBay for about $50 or new for $150 - $200)
4 Wheels (These can be quite expensive, new and second hand. A used set can cost you up to and over $100 on eBay)
4 Tires (You can find these on eBay, a new set can cost up to and over $300, but if you get a used set they can cost less than $100 or free)
Steering Wheel (You can get a cheap second hand wheel for about $20 on eBay)
Seat (You can use any seat you can find but we are using a fiberglass seat. You can get one on eBay for about $40)
Engine (We are using a mower engine which you can off an old mower or look on eBay for a few dollars)