ysrcflyer

From the original operating instructions:
The carb has 2 neddle valves fitted.
1- the high speed adjustment(high speed needle valve)
2- the low speed mixture control (idle needle valve) by throttle arm hookup

To set up this carb, it is useful to have a short piece of clean fuel line handy to blow thru.

The idle needle has been factory set and should only need minor adjustments for the correct setting. Don,'t lose the original setting before running.

The low speed setting is conntrolled mainly by the throttle stop and not the idle needle, which is only used to set the mixture.

It is best to adjust either the throttle stop or servo travel in the slow postion, so that the amount of opening is apprx. the dia. of a modeling pin. Now connect the fuel tubing to the fuel inlet nipple and set the high speed needle 1 1/2 turns open from the fully closed position. Now close the throttle and while gently blowing thru the tube, establish the setting of the idle needle where air just stars to escape. The correct idle setting will now be 1/2 turn open from this point. As a check on settings, if you, while still blowing thru the tube, open the throttle, you will find a rapid change in air flow when the arm has moved about 15 deg. from the slow postion. Don't use the idle needle to make a deliberately rich mixture in order to slow the idle. If you need to reduce the idle close the drum further and re-adjust the mixture by unscrewing the idle needle slightly

I hope this helps you, this is from the original setup inst. that I have.