My current Kart
This is the Kart I have at the moment with a Yamaha RXS100 engine. The wheelbarrow hubs are ideal for this type of off-road and general purpose Kart. They are nice and light been made from stainless, and as they have a metal bushing in the center, you can just weld the wheel straight onto the back axle, and not have to worry about having hubs. On the front all that has to be done is turn out a brass bushing to fit the axle and use split pins + washers to hold the wheel on. However if the Kart goes above 50mph the front wheels would wobble a bit.
An Earlier setup.
In this picture some might recognize the HONDA 5.5hp OHV engine. As this Kart was to be both an off-road and racing Kart gears would be needed and a much desirable manual clutch. So I set about "bodging" the engine up to an old Honda 90 which has 4 gears and an manual clutch. The only problem in this is that in using this setup I needed to have two chains and 4 sprockets. But the kart with its two chains ran very loud. Even though the whole setup cost me washers, I advise anyone who are trying the same setup, that to forget about it and just to get a motorbike engine. It's the best possible setup.
Another view of the above Kart