Sprocket Gasket?

[Nelsonmd]

So I took my sprocket cover off to try to fix my neutral position switch that hasn't been engaging correctly, and I found this rubber piece just sitting loose behind the cover.


It looks like it was attached to the outer side of the sprocket.


I don't see this part in the schematics, so I don't know what part number to order as mine appears to have half it's mounting points broken off and has split as well.

Also, what is the function of this part?