What exactly are the AMA bike classification rules? Big bike and lites. I see 250 2S racing 250'f in some cases. Are there race rules that are track specific allowing the track to pics what bikes are in what classes? Here is an excerpt from AMA... "In motocross only, new displacement limits would be applied to class 2 (100cc-144cc), class 3 (145cc-250cc) and class 4 (251cc and up). This means that both two-stroke and four-stroke motorcycles would be limited to the same maximum displacement and the limits would apply to A, B and C classes." OK so this means 144's race with mini bikes? No way a 144 2S makes almost twiuce the power of a 150R. I thouhgt 144 was made to compete with the 250F's? Argggg, It was easier with 2 classes 125's and 250's. Someone smarter than me clear this up for me please.