- seriously, what you will find out is that many places advertise an 80cc, but no one here seems to have actually seen one. What they report is an engine advertised as 80ccs, but actually is a little under 70ccs.
The term your looking for is the engine dimensions.
The problem is that there are many different dimensions associated with a motor. There's the cylinder dimensions, placement, and angle. the spark plug placement, angle, and dimensions, the crankcase dimension, the carb placement & dimensions, and the exhaust/pipe/muffler placement & dimensions.
If you locate these measurements, they're normally in the form of engineering outline drawings, viewed from two more angles. For instance, attached is the outline drawing for the Franco Morini S6-E engine