Hey Weld, it is a 47mm bore. I am not sure if true displacement is 70cc, or 72cc, since the same kit is listed on the scooterworks website in 2 places, yet under 2 part#s ( 1st part # being part od the "stage 2 kit", 2nd part# being just the piston & jug kit alone )
Here is a link to the actual piston kit used in the S2 kit:
http://www.scooterworks.com/prima-cy...p#.VZwXvGfbKpo
Also I changed the bottom picture in my original post showing the "right now" scooter as it sat this morning.