Police say the man was riding an unregistered blue Yamaha motorcycle along Maccauley Road, approaching Irrigation Way east of Wamoon, when the crash occurred around 3pm on Saturday.

"Approximately 130 metres short of the intersection, it would appear he has lost control of the bike, falling onto the bitumen road," Sergeant Cherie Knox said.

"As a result of the impact, the rider's helmet has dislodged, causing his head to hit the roadway."

Paramedics treated the man, who wasn't able to recall what had happened, at the scene before taking him to Griffith Base Hospital for further assessment.

"[That] assessment found bleeding and swelling to the brain, a punctured lung and a fractured scapula," Sergeant Knox said.

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The decision was made to airlift the man to St George Hospital for treatment, and as at 9am Sunday, the rider was in a critical but not life-threatening condition.

He also partially degloved toes on both feet in the crash, Sergeant Knox said, having donned slippers before getting on the motorcycle.