Re: Need Perm Woodruff Key Fix. Popped out twice in 6 miles
Strange that it's doing that because that's the idea of the half round key as opposed to a straight key, it can't come out when the gear is on, in other words there shouldn't be room for the key to slip out once the gear is on.
The only thing I can think of is the keyway is cut too far down on the shaft leaving more then half of the key exposed when the gear is on.
You could try a little dot of super glue in the keyway then drop in the key just make sure any glue that wicks out onto the shaft is cleaned up before you install the gear.