long ago i opened my dhoom engine its cylinder was labelled 78cc but when meausred its cc came out to be 86-88cc range. which classify it as 90 cc class engine.
so if new cHondas are coming with 86cm3 labelled on cylinder then either they are speaking truth or they are selling some higher cc bike as low ccs to mislead people by great performance from low ccs (in reality it might be 97cc who knows ? until one 86cc cylinder engine is opened and measured).