GASKET - ROTOR COVER TRIUMPH TWIN(Replaces 57-2442)

This is the gasket that seals the rotor inspection cover on the primary side of the engine, where the alternator rotor lives inside the chaincase. It's a small paper gasket that sits between the cover and the case, keeping oil in and dirt out while the cover stays removable for checking the rotor or timing marks. The catalog lists this as 71-1457, replacing the earlier 57-2442, and it shows up under the CHAINCASE AND CHAINS section in the parts books for the early-to-mid '70s twins. You'll also see it referenced by the alias E11457 or the older 4T designation if you're working from an earlier parts book. Cheap enough to keep a spare on hand, and worth replacing any time the rotor cover comes off, since a torn or compressed gasket is an easy way to start weeping oil at that cover.