whoa whoa whoa... backup....
that pic is essentially this:
forgive the crude sketch.
I can see a host of problems with that, mainly a carb that's way too big for the intake, tuning that is not gonna be like tuning a 4 pedal setup with a phbg at all, there are gonna be eddys and air pockets all over the place. who knows what jets u need.
what I would guess is happening is that since the carb is too big for the intake and at low rpms the intake charge is not strong enough to move air fast enough thru the carb to get the idle or pilot circuits working properly, thus you need to open up the choke a small side passage to get it to idle, but its then idling off a jet that way too big, and also causing your extra rich looking plugs (depending on how u ride when u are testing this all out).
just a theory, what do u think?