Set the idle screw (thumb screw with spring)so that the slide raises to about 2.5 to 3mm.

The more you screw your air/fuel mixture screw in the less air you get thus drowning (riching) your motor.  You need to move the screw out, not in, to lean the mixture.

Make sure your float height is correct and that you needle and seat arent worn.

Jess
Carb basic is checked,
Float lever and the jets are brand new.
its the same problem, my petcock is also brand new.
but when i left the quad for a week in my garage,
 i have a little fuel leak under my quad!

Replace the needle and seat.