There is a supercross track, and a long track that is the full supercross track with a little motocross track incorporated, as well as a stand-alone whoop pad.
Extract the files and place both track folders into your personal folder.
Track link: https://www.mediafire.com/?kpa153ppz7wuui3
Credit to Motoboss (I believe) for the grass clumps. I pulled them from the newest JT's backyard track and edited colors.
