Where are the motor bikes on Counterfeit Island?

The motor scooters are part of the chase sequence after you find the thief at the All That Jazz Club. This occurs after you are released from jail, get the time card from the guard at the Clown Store, and look at the surveillance videos in the Security Room at the Museum. Showing a photo of the thief (the shady guy who you thought was helping) to the mimes will tell you he is at the cafe.