The man, 39, remains in hospital following the incident on Wood End Avenue, in Wolverhampton, at about 8.20pm on Tuesday.
The driver of a black Vauxhall Astra stopped at the scene and is helping police with enquiries.
However West Midlands Police is appealing for more information following the crash.
Sergeant Dean Caswell, from the force's serious collision investigation unit, said: "Our enquiries are continuing to establish what happened that evening.
"I am really keen to speak to anyone who may have seen the black Vauxhall Astra or motorcycle before the collision took place and I would also ask anyone who has any dashcam footage of the collision to get in touch."
Anyone with any information is asked to contact police by quoting the log number 4448 of June 23.
Call 101, Crimestoppers anonymously on 0800555111 or visit the force's website.