The collision occurred on the B1257 Helmsley to Stokesley road near to the Laskill junction at around 2.30pm on Sunday 17 April 2011.
The motorcyclist, a 62-year-old man from Driffield, sustained serious injuries when his silver Honda CBR bike, which was travelling towards Helmsley from Stokesley, collided with a blue Kia Sorento, travelling in the opposite direction.
He remains in James Cook Hospital, in a poorly condition. The occupants of the Kia were uninjured.
Traffic Sergeant Clare Sawyer, of Thirsk Road Policing Group, said: “I am appealing for anyone who witnessed the collision to come forward with information.
“Anyone who saw the motorcycle, or the Kia, which was towing a caravan, prior to the incident may have information vital to the investigation.”