This listing is for an optional Shim that can be fitted in front of the Selector Pawl mechanism - to further improve slickness of gear selection, when used in conjunction with the A11/415 (which we also sell - Item 0851.
It is important to say first - this item is not listed in either the Norton 1948 Spare Parts List (i.e. upright gearbox) or the 1955 ES2 Spare Parts List (laydown gearbox) (see detail listing for information) - so I am not sure that Norton's fitted this shim from new.
However, the A11/415 shim (Item 0851) is shown, and is often missing from gearbox's now . . . as it is often omitted or lost on re-assembly. Therefore, if stripping or inspecting your selector mechanism - it is most important to find that is fitted first, as it improves smooth gear selection. The A11/415 shim fits behind the selector pawl ratchet plate
But over the years I have also stripped other gearbox's and found a shim similar to this one fitted in front of the selector pawl ratchet plate - it being identifiable by having a smaller inner diameter than the A11/415. This may have been fitted by later owners of those gearbox's as wear has developed - so if fitting this shim, it is important to confirm that as you tighten the outer pressed steel Return Spring Cover Plate you still have free movement of the selector pawl ratchet plate - but this being the case, this shim should also help provide a smooth movement of the selector pawl - particularly if both shims are smeared in grease as they should be.
In the accompanyning photograph, you will see the shim fitted to an upright gearbox selector mechanism on the left and a laydown gearbox selector mechanism on the right
Likewise, if the selector pawl and ng a smooth