I have a musketeer with an O-320. I have a stumble also. I had the engine
overhauled (not because of the stumble) and it still does the same thing.
My opinion is that it is associated the intake manifold geometry. I am no
expert.

"Dave Butler" wrote in message
news:1133797784.923574@sj-nntpcache-3...
snip
I was told there is a transition in the carburetor at about 1500 RPM, and
that many of these engines will stumble across this transtion. Maybe it's
a transition from the idle jets to the main jets(?), I don't know what I'm
talking about.

Anyway, I spent a lot of time and money trying to diagnose this symptom in
the Archer. Two owners later, the airplane is still around at my home
airport, and I'm told it still has the stumble. It gets you when you're on
short final and reduced power, and decide you need a little more power to
get to the runway.

Dave