Where is the FUEL MIXTURE Screw?

Not the idle screw on the Head but the fuel mixture screw. you see, since i cleaned flushed and replaced all filters etc shes running far to rich and i need less juice to the head? loads coming out the exhaust- not good!  :dontknow:

it's located between the fuel metering unit and the round rubber dome of the air intake

fairly long, round tube, need a 3mm long allen key

ill give it a try then cheers.