The man was rushed to hospital after the incident on Shooters Hill Road around 4.15am yesterday (February 24).
A spokesperson for Metropolitan Police confirmed today (February 25) that he remains fighting for his life 33 hours later.
London’s Air Ambulance and the London Ambulance Service attended the scene alongside police officers.
No other vehicle was involved in the crash.
The road was closed between the junctions of Charlton Way and Stratheden Road but has since reopened.
A Metropolitan Police spokesperson said: “Anyone with information, including dash camera footage which may have captured the incident is asked to call 111 quoting the reference 712/24FEB.”