The collision occurred just after 5pm on Friday (6 January).
It’s believed that the biker rode the wrong-way up the one-way High Street and hit the man near to the junction of Queen Victoria Road.
The casualty has been taken to hospital with multiple fractures to his body and face, and is currently in a stable condition.
A spokesperson from Dyfed Powys Police said: “Despite coming off the bike himself, the rider left the scene and we are now trying to identify him.
“We don’t currently have a detailed description, but he is believed to have short brown hair and was wearing dark clothing, a lime green helmet and carrying a grey rucksack.
“The bike is described as black, and is an off-road style vehicle, which left in the direction of the town centre.
“If you have any information that might help us to find him, or if you are the person involved, please get in touch.”
(Lead image: Google Maps)
