The 44-year-old Berry man suffered back, leg and shoulder injuries during the incident, believed to have occurred after he lost control on an oil slick.

Last August, authorities branded Macquarie Pass a motorcycle black spot after 144 accidents and six deaths in five years.

The injured man was travelling up Macquarie Pass with a companion rider just after 11.30am when the accident occurred.

He rounded a sharp bend before being speared from his red Honda Fireblade over the edge of the pass and several metres down an embankment.

One of the first on the scene, a 59-year-old Sydney man who was also on a motorcycle, rendered first aid and made the man comfortable until emergency services arrived.

"He said it happened so fast it felt like he hit an oil slick which high-sided him into the bush," the rider said.

"A log broke his fall which is lucky because he would have had a very nasty trip further down. There were a lot of tree stumps, roots and branches in the way."

Members of the NSW Fire Brigades Rescue Unit, Police Rescue, ambulance and NSW Rural Fire Service attended.

The rider was taken to Wollongong Hospital in a stable condition. Traffic was disrupted for about two hours.

Shellharbour City Council joined with police, the RTA and Illawarra motorcycle groups last August to try to reduce the accident rate after Macquarie Pass was branded as a motorcycle black spot.

Those most likely to be injured or killed on the road were men returning to motorcycle riding later in life. All the fatalities involved males aged between 30 and 60.

An RTA campaign targeting the state's 130,000 motorcyclists was launched in November 2007 and urged caution on popular routes such as Macquarie Pass.

He said the Illawarra Hwy through Macquarie Pass was a common spot for accidents because of the sharp corners and marginal distance between the edge of the road and trees.

Frequent diesel spills on the roadway have added to the danger.

The Pass has been closed to traffic on weekdays since last Monday while the thoroughfare undergoes maintenance including resurfacing, vegetation management, signposting upgrades and drain cleaning.

The closures will continue until Friday.