The motorcyclist is said to be aged in his early 20s and was wearing light grey tracksuit bottoms with a double light blue stripe down each leg, a black jacket and black gloves which had plastic caps on the knuckles. He was also wearing a green and silver crash helmet.
The bike he was riding is described as a black and green off-road machine with Evo-Tech written on the front shocks.
An appeal for witnesses has been made after a dog walker reported he was assaulted near the Crabble football ground in Dover.
The 41-year-old man from Dover was walking his dogs on the hills near the football ground when a motorcyclist came up behind him on a footpath.
Concerned for his dogs, which were off their leads, the man tried to stop the motorcyclist who became annoyed. He is then said to have got off his bike, sworn at the man and punched him in the face, causing a black eye.
The assault happened at about 3.45pm on Saturday 27 April 2013.