I agree with Nina with regard to UK usage.
For British English speakers, 'motorbike' is the usual everyday term.
'Motorcycle' is the more formal term. You would see this in official notices, such as police signs about where you are allowed to ride or park. In the UK, it would sound rather odd and old-fashioned to say 'motorcycle' in normal conversation. I believe this would also be the case in Australia, NZ and other countries which use predominantly British English.