hmm, went to zamacarb.com and the page came up without a visible image displayed.
hit the pdf option to get "foxit reader" to open the pdf file, was the typically un-helpful
"image not necessarily representative of actual part" sort of disclaimer (grumble).
couldn't see anything resembling an adjustment screw
and no mention or visualization of moving the needle in the center of the barrel.
If the needle has no threaded manor of adjusting, but isn't permanently
affixed
i.e. molded into the barrel plastic or using some other method of confinement
For those lean conditions:
we may still have the option of "shimming" it upward
with some tedious method of disassembling, fiddlement then a trial run..
repeat process till satisfied....
If we've got a rich condition, obviously it's a bit harder to lower the needle
in a precise or repeatable fashion.
so often then you're into trying plug nozzles (epoxies, etc) and reopen
to smaller diameter with the same try it, tear it down again, assemble & try it again loop.
back in the days of dirt biking (you could purchase various carb parts then) people would even end up taking a larger (which would cause leaner mix)
and spinning it in a drill to facilitate very lightly sanding a butterfly kiss
worth of metal off to re-contour the needle profile.
the way those old sliding barrel type carbs flowed meant the needle
overlapped and affected a very wide range of the throttle range
( somewhere around 20% open, up to full throttle)
and we needed a lot of fine tuning for motorcycle operation of course
so thus the chasing of the shape and flow characteristics of the needle
and the emulsion tube diameter and shape, etc....
I think we'll find the rotary barrel carbs will respond in a similar fashion
as the old Mikunis and Honda's ubiquitous keihins
look at the way a starting lever raises the barrel
(but not opening the effective venturi size )
to get the needle lifted for a slightly richer mixture for cold cranking.
just gonna be a pain to work around the engineering/manufacturing efforts
that are in place to prevent us from it.
If the barrel types are set up correctly,
It's just seat of pants anecdote here,
but I think they give better response and running
than our well known and loved shaft & plate type carbs.
just wish they weren't being morphed into a modern analog (correct term?)
of a Tecumseh fixed jet/body orifice,
no choke gotta use the damn punch-bubbles carb
of the later Craftsman products before Tecuseh went under.
Hopefully I've stirred some helpful contemplation of the little buggers
with my missives here.