idealy, you want a motor to be somewhat square, meaning that the bore and the stroke are close to the same. you get a short stroke, big bore it will rev QUICK but you will make no torque. the longer the stroke the more torque you will make but most of the time the motor will not rev as quick. you combine a long stroke and a big bore and you will have a long broad torque curve with good hp numbers as well. there is a little more to it than what i just posted but that is the jist of it.