Four speed electric start models with rear belt drive, 1979-1984, splined engine shaft, 1 1/2 inch belt. These 11 mm primary belt drive systems fit most Harley Davidson Big Twin 1937-1984 with 4 speed transmission (except #77113 which fits 1980-1984 5 speed) open/closed primary. A proven concept has been used in manufacturing these belt drive systems, that of using more teeth on both pulleys combined with a brand new Gates belt designed for this particular pulley combination. It uses a front pulley with 31 teeth and a rear pulley with 47 teeth. Manufacturer