What are the difference between these three? (80cc, 66cc, and 49cc). I mean, I know that those are displacement measures, but I really want to know is which are the differences because I was told there was no visible difference when looking at the exterior of the engine. I want to tell which one's which 'cause I don't want to get fooled by the vendor which occasionally happens here in my country. Secondly they've told me there's no such thing as a 80cc engine, that it is really a 66cc... Is that true? Thank you very much in advance people!!! Happy biking!!!