I had a similar problem and I got so tired of it doing that, I accidentally figured something out.
Now I can't recommend you do it, but just like yourself I replaced the carburetor and hence had a spare...
That wasn't the only thing I had replaced but long story short I was a bit pissed, so one day I took a
needle nose vise grip and clamped it on to the HIGH adjustment screw, the plastic part.
Then I turned it up to where the plastic hits that stop and kept going until that POS
plastic sleeve broke and allowed the adjustment screw to go past the stop.
Once that was done it was easy to adjust it, and I got it running pretty good
with the high end screw somewhere past the manufactured stopping point.
Doesn't run 100% perfect but it's close enough for me.
As I said I can't tell you to do that, but when I asked about this at the dealership they said the procedure isn't unheard of.
I also heard other folks saying you just have to learn how to 'adjust' it...
Mine's an FS-80r, 2001 model.