Since no one else could answer your question...............

stroke x bore x bore x .7854

For example here's a 200cc configuration:

57mm is the stroke and 66mm is the bore size, you move the decimal 3 to the left.


57 x 66 x 66 x .7854 = 195008.53 your final cc is 195, or as most manufactures do, they round it off higher to 200cc