For an engine with a 1" diameter bore, the area of the top of the piston is pie-r-squared, so 0.785 sq.in.
Assuming a clearance of 1/16", then the volume at TDC would be 0.04906 cu.in.
For a 20:1 ratio, then the volume at BDC would be 0.98125 cu.in.
So 1.25" stroke.
My math is off somewhere.
Somebody help me.
.