AMA Motocross Championship

The AMA Motocross Championship (the "outdoor series") season begins in early May and continues until mid-September, and consists of twelve rounds at twelve major tracks all over the continental United States.There are two classes:^[13] the 250 Motocross Class for 0–125 cc 2-stroke or 150–250 cc 4-stroke machines; and the 450 Motocross Class for 150–250 cc 2-stroke or 251–450 cc 4-stroke machines.