60HP two stroke control puzzle

I have a rebuilt 60 HP 2 stroke using mix gas. when slowly reducing power from full to idle speed the motor responds to throttle slowing to about 2900 rpm and further reduction of the throttle lever causes an increase of speed to 3400 then comes back down to 2400 then at 1500 beginns to run ragged and rough till full idle at 800 where it smooths out.
New controls, new computer, coils, thermostat, head and exahust gaskets, new plugs, using ringfre.

Nothing helps. Any idea or similar experiences?

rsettineri1@mchsi.com

[99yam40]

go through the carbs and then make sure you do a link and sync like the manual says