The victim, a 63-year-old man, was left with minor injuries to his face following an assault which saw two men steal his wallet.
They were reported to carry out the attack at around 8pm on Monday, February 24 on a footpath between Trevelyan Avenue and Blyth Sport Centre.
The pair then fled across the sports centre car park on the same bike, with one man riding the bike and the other sitting on the handlebars.
PC David Ostle said: “The car park was really busy at the time of the robbery, with lots of people coming to and from the sports centre, so we’re asking anyone who might have seen the two men fleeing on the bike or hanging around before, to get in touch.
“The smallest detail could be crucial to our investigation.”
Contact 101 using reference 1023 24/02/20 or Crimestoppers on 0800 555 111.