A Yamaha R6 was taken from outside a property on Sutton Road overnight on July 9-10.
A Lincolnshire Police spokesman said: “We would also like to speak to the two people in the photograph, who may be able to help our enquiries.
“While we acknowledge that the quality of the image is relatively poor, it contains some features that people may recognise.
“Anyone with information should call 101, quoting incident number 26 of July 10.
“Alternatively, contact Crimestoppers, anonymously, on 0800 555111.”