are the 70cc & 80cc the same?

I have a 70CC engine with 8mm headstuds & I know the 80cc uses 6mm headstuds & a thinner headgasket but is the cylinder really larger?
if it is can I put one on my 70cc engine?

also does anyone have 70 or 80cc rings & cylinder as a set?
I had to ride mine in heavy rain a few weeks back & today when I pulled the head off to put in the thinner gasket I found some small gouges near the top of the cylinder
its running well but Id like to have it rite
take care
JAK

the "80cc" chinese bike motor is a fantasy....they do not exist. i dont trust any seller so blatantly dishonest about displacement. makes me wonder what else they're not saying truthfully.
they're all closer to 67-point-something cc's. Dax motors use the 8mm headbolts, on 70cc as well as 48cc.

pretty much all others that i know of use 6mm headbolts, 48cc or 70cc

EDIT: the last few motors i've gotten from different factories have been 8mm

__________________
New, fully assembled motored bikes here: http://happytimecycles.wordpress.com/
401-952-7064