Officers were called to Halifax Road at 10.50am on Sunday, 11 October to the A629 Halifax Road, near to the junction with Manywells Brow.
A White Volkswagen Caddy van and Black BMW motorcycle were in collision.
The rider of the motorcycle Richard Grant, who was 70 and from Sowerby Bridge suffered serious injuries.
He sadly died from those injuries on Monday, 30 November.
His family have released the below photograph.
A female passenger on the motorcycle suffered serious injuries.
She has since been released from hospital.
The driver and passenger of the White Volkswagen Caddy van were not injured.
Officers would like to speak to anyone who witnessed the collision, or who saw either the White Volkswagen Caddy Van or the Black BMW motorcycle prior to the collision to come forward.
Officers are also keen to speak to anyone who may have 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.