Police were called by the ambulance service at around 12:15pm on Saturday 13 October 2012 after the cyclist was found injured on the road.
The cyclist, who is from the local area, was airlifted by the Yorkshire Air Ambulance to Leeds General Infirmary with serious head leg injuries, where he remains in a critical condition.
Police need to establish how he sustained his injuries and are appealing for anyone who saw the cyclist riding along the B1222 or saw him fall or collide with anything, to contact them.
Traffic Constable Martin Hayes of Tadcaster Roads Policing Group is investigating the incident, he said:
The man has suffered serious injuries and I need to establish exactly how he sustained those injuries.
Information from the public is vital in piecing together the sequence of events which led to him falling from his cycle and I am appealing for anyone who was on the B1222 at Cawood and saw what happened to contact me as a matter of urgency.
Anyone with any information is asked to contact TC Hayes by calling North Yorkshire Police on 101, select option 2 and ask for Martin Hayes, or you pass information via email to email@example.com