Good point! if the drive key tries to roll out of the slot in the crankshaft, it can lock up the balancer partway on. The fix is to pull the balancer back off, and be sure the key is a snug fit in the crank, and a slip fit in the balancer slot.
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
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