A guy just asked the same question on another forum. I am pretty sure you can work something out with a kart track for something like that, I am sure they will welcome it since you provide your own equipment and gas.
The cheap ones starts at under $200 for an air cooled 2 stroke, there are also 4 stroke models and ones with full suspension. It is actually cheaper than most R/C cars…LOL
I am totally down for it, since I am planning to get one as a pit bike anyway.