^^^ there is a difference. what kind of racing do you need a helmet for? i have a helmet that is motorcycle rated but is not rate for track racing. its good enough for NHRA drag racing to a cirtain time i believe. but there are different rating that make a difference to track officials. here is a sight that can help. If your looking for a motorcycle helmet for drag racing purposes i have one i can sell you. used only twice. size M though (have a smaller head) if your looking to race on a road coarse or circle track this helmet doesnt meet those standards...
http://www.smf.org/stds