Difference between 80cc, 70cc, and 67cc

I see that the 80cc engine is really a 67cc. So what is the difference between the 80 and the 70, and 67cc?
I'm guessing they're all pretty much the same, just a differnent name and price?

Please enlighten me!

They are all the same. SOME mfrs have a 69cc and the rest are a 67cc. But yeah...it's all marketing otherwise.

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48cc Giant. 50T, 26" wheels, catalytic converter-Built for Younger brother.

66cc Trek 800. 44T, 26" wheels, cut baffle. Top speed 35.0mph.

They are all the same.

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If it ain't broke, and you mess with it long enough, it will be.

Truth in advertising is the only difference.