To answer your question.... The Chinese engineering culture and the sales reps refer to their engines as 80 cc. They are referring to the volume displaced by the moving piston (about 66 cc) plus the volume of the space under the cylinder head that the piston does not intrude upon. All engines have some kind of head space.
In America, engineers label the displacement of an engine as the volume swept by the movement of the piston alone (about 66 cc). It is always less than the Chinese method of measuring displacement.
I have not done head volume measurements for myself, just swept volume. If you are right, the engine measurements add up to only 71 cc. If so, the compression ratio computes out to be over 14:1. That is too high for me to believe. As many times as 80 cc has been posted by engine builders, I will go with that figure until I measure for myself.
