Another possibility, if the carbs have been sitting idle for a fair while, is that the idle circuit has got a slight build up of "petrol plaque" that is leaning out the idle circuit.
A bit like having a build up of fat on the walls of the arteries leading to the heart I guess? Or something like that.

I can vaguely remember a friend who put an old carb on a single 4 stroke, about 10 years ago, having a similar problem.
He cleaned out the carb to no effect, but after a few hundred miles the problem went away.

I think what happened is that the "petrol plaque" was too stubborn to be cleaned off, but slowly and surely dissolved away with use.
Hence, zero to 1/8th-ish throttle response was restored after riding the bike for a few hours.

Had your carbs been siting idle for a fair while?
If so, maybe just put a few hundred miles on it and see if it fixes itself??
Wishful thinking perhaps?
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[color=#808080][size=9]Yes,.. I too know how to waste Time and Money,...