Shane Connor was described last night as "serious but stable" in Noble's Hospital, following a crash at Alpine Corner in yesterday's Junior Manx Grand Prix.
A further update is expected later this morning.
The 23 year old rider was in second place, when he came off his bike on the third lap.
The section of road between Kirk Michael and Ballaugh was closed for a period after racing finished.
Connor was riding for the JD Racing Team - the owner John Donnan was tragically killed at the Tandragee 100 meeting in early May