Richard Grant, 70, was involved in the crash between the motorbike he was riding and a van on Halifax Road in Cullingworth.
Mr Grant, of Sowerby Bridge, suffered serious injuries after the crash at around 10.50am on Sunday, October 11, near to the junction with Manywells Brow.
He sadly died from those injuries on Monday, 30 November.
The crash involved his Black BMW motorcycle and a White Volkswagen Caddy van.
A woman passenger on the motorcycle suffered serious injuries.
She has since been released from hospital.
The driver and passenger of the van were not injured.
Officers want to speak to anyone who saw the collision, or who saw either the White Volkswagen Caddy van or the Black BMW motorcycle before the crash, to come forward.
Officers are also keen to speak to anyone with dash cam footage of the incident.
Information can be given to the Major Collision Enquiry Team via 101, or use the contact us options at www.westyorkshire.police.uk/contactus quoting reference 13200509267.