My guess, and it's just a guess, is that you flooded the primed cylinders
while the remaining cylinders fired and operated normally, thus the
roughness.
As you advanced the mixture, the primed cylinders continued to be flooded
but the non-primed cylinders operated normally, albeit at a possibly rich
mixture.
As you retarded the mixture, the primed cylinders were then able to
completely burn the leaner mixture and clean themselves up.

This makes as much sense as anything -- thanks.

I probably shouldn't have used the primer at all, but it was in that
goofy, "in-between" length of time, where the engine wasn't really
still "hot" -- but it wasn't really "cold" either.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"