Early model belt drives featuring the ultra severe-duty 11mm Aramid Polychain belt. These belt drives are designed for enclosed primary fitment, either within aluminum primaries or within tin (stamped steel) covers. For the later aluminum primary models (1965-1984) two kits are offered for kickstart and electric start models. The earlier tin primary models are available for tapered (1937-1954) or splined shaft (1955-1964) applications, kickstart only.