ADAPTER 3K3428 - Caterpillar

Generators Equipped With Small Brushless ExcitersAll SR4 generators now have a 3/8" keyway for alignment between the rotor shaft and the exciter rotor. The 1/2" keyway was previously used.
In order to service SR4 generators in the field:
...parts replacement of the main rotor will include an exciter rotor with a 3/8" inch key.
...parts replacement of an exciter rotor will include two keys: a 3/8" key and a 1/2" to 3/8" stepped key. The 3/8" key can be used for the new main rotors having the 3/8" keyway. The stepped key can be used with the former main rotors with the 1/2" keyway.
The exciter rotors with the following part numbers will be supplied with two keys:
5N6496 Rotor Core Assembly.5N6497 Rotor Core Assembly.5N6498 Rotor Core Assembly.5N6499 Rotor Core Assembly.