Yes the Go Karts and 4 wheeler use what they call the short case version and they are normally set up for a 40 or 420 chain but the CVT belt runs to a assembly or gear box that goes to a chain drive down to the axle, some of the go karts even have a reverse....
wouldn't that be wild on a bicycle..!
The short case engine are higher too.
A stretched out bike frame and a well built jackshaft set up would be the way I would go with a long case engine if I were to build one, get the splined inset from a rear wheel and weld the desired sprocket onto that and then a chain from there to a jackshaft and from there to the wheel is the first design that comes to mind without thinking to much about it.
loads of parts
Here is a little info you may find interesting about the GY6 and a place that sells some stuff for them also.
Can you say 12,000 RPM 4 stroke capability...LOL!