Originally Posted by
operator
The keyed washer is not needed and major fail. The only thing it does is slip and take fork threads with it. ALWAYS replace with a non keyed washer.
It sounds like the OP has one of those headsets whose keyed washer has saw-tooth serrations that mate with corresponding sawtooth serrations on the top race, like this:
Not sure how you would get rid of the keyed washer there since the top cap would slip on those teeth, and you can't grab the adjusting race with a wrench to keep it from spinning while you tighten it.