Oil Seals

Shaft seals for main bearings

Before the introduction of recirculating lubrication on Harley-Davidson engines, sealing the crankshaft to the outside was not even really useful. The fresh oil lubrication provided sufficient supply and, in addition to the oil mist from the engine ventilation, the oil escaping from the left crankshaft bearing also provided lubrication for the primary chain.

At the end of the 1930s, however, the recirculating-lubricated engines were gradually fitted with proper sealing of the crankshaft bearings by means of oil seals.

Oil seals

Oil seals (the DIN standard calls them radial oil seals, the mechanic commonly refers to them as Simmer rings in memory of the ingenious Austrian inventor Walther Simmer) are combinations of a metal housing with a spring-loaded sealing lip. Most damage to the sensitive sealing lips does not occur during operation, but due to carelessness during installation and removal of the sealing ring or shaft. For this reason, and because it is a wearing part, we recommend replacing it every time the crankshaft is removed from the engine housing.