At about 5.20am yesterday a grey Mazda Tribute was travelling south along Rusden Road and stopped at a stop sign at the intersection of Old Bathurst Road.

At the same time a black Kawasaki motorcycle was travelling east along Old Bathurst Road.

Police say the Mazda drove through the intersection to turn right into Old Bathurst Road, with the two vehicles colliding.

The 38-year-old Faulconbridge rider was thrown from his motorcycle onto the roadway, suffering from fractured ribs and a fractured wrist and a serious knee injury.

Police say he was taken to Nepean Hospital in a serious but stable condition, undergoing surgery.

The 39-year-old Mount Riverview driver of the Mazda was not injured.

Officers from the Metropolitan Crash Investigation Unit are making inquiries into the cause and are appealing for anyone with information to contact them on 8882th1458 or Crime Stoppers, 1800th333th000.