Shovelhead final belt drives
Harley-Davidson started using final belt drives in 1980 with the introduction of the FXB "Sturgis" model. By 1987, all Big Twin HD models were equipped with final belt drives. The sportster models gradually switched over a little later, and by 1994 all HD models came from the factory with a final belt drive.
Check out these links below for some more background information on shovelhead final belt drives: