East of Ronkonkoma near Yaphank, the Long Island Motocross (aka Island Motocross of NY) has a motocross track and a PeeWee track.
To reach dirt biking at Island Motocross of NY from NYC, follow the Long Island Expressway to Exit #65. Head east on Horseblock Road. Just past the Sunoco gas station, look for the entrance on the left at the light.
Overall, Long Island MX is the 6th most popular dirt bike trail of all 30 dirt biking rides in New York.