... engine kit Two Stroke Center-install Bicycle Engines Engine ZM50-P(4stroke) ZM60-P(F60)2 stroke ZM70-P(F80)2 stroke Type one ... engine in china market, we called our 47*38(bore*stroke) engine F80 before ,but now we correct it, because ... listed below. The volume of a cylinder=(bore area)x stroke Bore area= Bore x Bore x pi / 4. ( ... for example, its bore is 4.7cm(47mm), its stroke 3.8cm(38mm) 4.7×4.7÷4×3.14 ...