Friends performed CPR on the 30-year-old after they found him semi-conscious on Ocean Beach around 3pm on Sunday.

Initial police investigations indicate the man from the northwest struck a buried log.

"The bike remained upright for some distance afterward, but eventually it did come to rest on its side," senior sergeant Adam Spencer said in a statement.

The alarm was raised when the man failed to rendezvous with friends, with one rider activating his personal locator beacon on the beach.

The man's friends were performing CPR when police and ambulance crews arrived, sergeant Spencer said.

"Paramedics took over, but despite everyone's best efforts - he unfortunately died at the scene. Our thoughts and condolences are with his family," he said.

The crash is being investigated and a report will be prepared for the coroner.

Australian Associated Press