One machine to build a mini bike track

Skid steer

Agree with Skid steer (with tracks), get one that is at least 8 or 9K pounds, you might even be able to tow it yourself to save dollars on a delivery charge. With a decent size machine and 1 acre you could build a pretty nice little track in one day if you are decent at running the thing. Make sure the loader bucket on the front has teeth (not smooth) for digging.

What's the dirt? Loose, packed, clay, sand? Skid steer ok if dirt is right, and it has a ripper. 30 HP tractor with a bucket, ripper, and tiller might work well too. You can build small jumps and good bowl turns with either. Each does a better job at certain types of finish work. Supercross style or turn track or ????

Hammer 663s.

Definitely skid steer or skip if that’s not an option

X2

PawPaw

Yup, big track dozer hands down. Mini track - tracked skiddy. Second would be a front end loader tractor mainly because implements are numerous & cheap.......That said doing the basic layout with a 450 sized dozer would expedite things immensely unless dirt is sand/soft then finish with skiddy.........

skid steer. and one with tracks instead of wheels.

Definitely a compact track loader.

Where is the dirt coming from? Native or being trucked in?

If you never ran a skid steer before plan on at least 1/2 day wasted on figuring things out. Amazing how quick someone that has experience can move dirt and make it look easy

Cat 289D Compact Track Loader or the equivalent.