First of all it's not called cylinder ma bore.......displacement in cc/cm3 is basically bore^2 * stroke * number of cylinders
Engine displacement is the volume swept by all the pistons inside the cylinder of a reciprocating engine in a single movement fromtop to bottom.
Secondly you are right the engine displacement of a Honda CD70 is 68-69cm3(72cm3) but i doubt that of chondas is 86.
Most of the chonda's say 78cm3 on their heads but max they may be 80-81. Also the head of union star 2014 says
86cm3 but highly doubt it is different than the other chondas and most probably 81cm3 at max.