Yup, got a small flat-head screwdriver? Sounds like your problem may be easy to fix! I have never had an engine (new or used) that did NOT need the idle mixture adjusted.... I like to start also 1/8th of a turn at a time- I start it tune for full thr. quickly then go to idle, let it idle for 30 seconds (or as long as it will idle reasonably) then advance the throttle QUICKLY- if it sputters it is rich and you need to go another 1/8th lean (clockwise) if it just dies purty quick it was too lean- (probably not the case with yours-)

Start it up again and repeat- Keep doing that until your transition is as fast as you move the stick!

Keep us posted!