Ryan MacLeod, aged 21, is believed to have been involved when a 32-year-old man was attacked in the outside smoking area of the Castle Howard Ox, on Townend Street, in November 2012.
MacLeod is also wanted for recall to prison after breaching the terms of his release licence.
He is believed to have links in the Manchester area and officers have been checking addresses there and in York for any sign of him.
Police are also appealing to the public to help find MacLeod and are urging them to report any sightings of him.
Detective Inspector Dave Kirby, of York police, said:
If Ryan MacLeod thinks we are going to stop looking for him, he is very much mistaken. In fact it is quite the opposite – we will keep looking for him until we find him, no matter how long it takes.
If you are helping Macleod to evade the police you can expect a visit to your house and you will be arrested as well. It is an offence to help a wanted man and the longer Macleod is at large, he is making things worse for himself and any associates who are assisting him.
MacLeod has shown a blatant disregard for the criminal justice system and I urge the public to help us to find him.
Anyone who can help officers to locate Ryan MacLeod is urged to contact North Yorkshire Police on 101 – select option 2 – and ask for York police.
If you wish to remain anonymous, Crimestoppers can be contacted on 0800 555 111.