Ding ding diiinnggg winner!! thats why bikes can still be made and quads can't. But in truth thats just a lame excuse for them to make 4stroke becuase they make more money that way, sleds and pwc's are under the same laws and pass the epa with flying colors!Quads aren't considered closed course race machines so if they don't meet the epa emission laws then they can't be sold in the u.s.