It depends on many factors, such as modernity of the engine, whether it is fuel-injected or carburetted, gearing set-up, driving style, preferred mode of operation (city, or motorway/rural).
In a similar conditions my FI 250cc Suzuki TU gets twice better economy than my father’s carburetted 800cc Kawasaki Vulcan (2.8 L/100 km v. 5.4 L/100 km). Weight is probably the biggest factor. In my example the displacement goes up more than threefold, but the weight of motorcycle with rider only goes from 235 kg (150 kg bike + 85 kg rider and gear) to 340 kg (245 + 95) — only 40% increase.
In the city I much rather prefer my nible standard, but for the sustained motorway journeys bigger bike would do a lot better (and shall get better economy in comparison to city riding, as my small bike’s RPM get too high going close to 90–100 km/h and up).
To check specific models’ real-world fuel economy, browse all motorcycles at Fuelly.