It appears that it snaps around the shaft and holds it in one direction against t the pivot bracket to prevent it from shaking back and forth. I've got about a dozen engines stockpiled- - - -I'll see if I can find one that still has it in place.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!