Emergency services were called to Rye Road, near the Hastings Academy, at about 1pm on Saturday, October 8.
A red car involved in the collision failed to stop at the scene.
The passenger travelling on the motorcycle suffered serious injuries and was taken to hospital for treatment.
Anyone with information or footage relevant to the investigation is asked to email collision.appeal@sussex.police.uk, quoting serial 567 of 08/10.