Stone

Stone is a 1974 Australian film produced and directed by Sandy Harbutt. It was a low budget movie, written by Sandy Harbutt and Michael Robinson.

Police officer Stone goes undercover with the Gravediggers outlaw motorcycle gang, to find out who is murdering their members, one by one.

The film stars Ken Shorter and features Rebecca Gilling, Bill Hunter and Helen Morse. The film's soundtrack was composed by Billy Green and featured some members of his group Sanctuary. Motorcycles featured include the legendary Kawasaki Z1(900). Stone initially rides a Norton.
Plot:

When several members of the GraveDiggers outlaw motorcycle club are murdered, Sydney detective Stone (Ken Shorter) is sent to investigate. Led by the Undertaker (Sandy Harbutt), a Vietnam war veteran, the GraveDiggers allow Stone to pose as a gang member. Leaving behind society girlfriend Amanda (Helen Morse), Stone begins to identify with the Undertaker and his comrades Hooks (Roger Ward), Toad (Hugh Keays-Byrne), Dr Death (Vincent Gil), Captain Midnight (Bindi Williams), Septic (Dewey Hungerford) and Vanessa (Rebecca Gilling), the Undertaker's girlfriend. Amid violent confrontations with the Black Hawks, a rival gang the GraveDiggers hold responsible, Stone uncovers a political conspiracy behind the killings. When the truth is revealed, Stone must choose between his job and his loyalty to the GraveDiggers.