It looks like 8.23 to 1, Thats from the numbers you gave. Normal stroke is 3.75, I think thats what you have.
I ran it again on KB's website. It came out to 8.26
.043 Gasket
4.360 bore (4.32+.040)
3.75 stroke
.146 piston depth
80cc chamber
4.40 gasket bore
0 piston volume (flat tops)...