A 23 or 26 will seam faster than a 30.5 because it will rev to higher RPM than the 30.5. The 30 will make more TORQUE than the others but in the end it's HP that makes speed. HP is equal to torque x RPM / 5250. From that formula you can see that if torque stays the same,all you have to do is raise the RPM and you get more HP. To your CC question,a bigger engine will make more torque but the longer stroke limits the RPM,and since a Baja or whatever doesn't have a transmission to keep the engine in the narrow RPM range were it makes power,even if it's more power than the smaller engine,the one that will rev higher [the smaller engine]will reach a higher top speed. Clear as mud?