The 39-year-old Nowra man, alleged to have stolen a motorcycle, was riding along Adelaide St when he lost control of the bike and slid into a garden bed on Sunday afternoon.

A metre-long piece of timber was driven through his right armpit and out of his back.

A puncture wound was also found on his leg.

It was believed the owner of the bike was in pursuit and, upon catching up with the rider, pulled out the stake and punched him on the nose before reclaiming the bike.

Ambulance officers who responded to reports of a man with a garden stake in his torso arrived to find the man conscious.

The stake had been removed.

The man was airlifted to St George Hospital, where he was admitted suffering internal injuries and a suspected broken nose.

Police confirmed there was no motorcycle at the scene when authorities arrived.

Yesterday, a Nowra police spokesman said the fact there was no longer a motorcycle did not mean the case could not be investigated.

He said there was no reason to suggest the bike had been stolen from a motorcyle gang member, as had been alleged.

Police have yet to interview the injured man, who was still in hospital yesterday. He is said to be in a stable condition.