Terry – be careful what you wish for by inviting Council onto the site, but in any case I doubt they could do anything about the problem unless the motor bikes are parked within designated visitors’ spaces or they’re encroaching upon designated passages of entry, egress, and maneuvering for vehicles within the carpark; both of which would be conditions of their Development Consent.
If you feel strongly about the matter, and particularly about your E/C’s unpreparedness to do anything about this Breach of a By-Law (i.e. parking on common property, where by the way “consent” relates to a specific instance such as loading / unloading a vehicle and not a regular occurrence), then consider taking your Owners Corporation to Mediation using THIS form or by using the services of a Community Justice Centre.