With motor idling, adjust carburetors one at a time.
First locate the adjustment screw just in front of the accelerator
pump on the right side of each carburetor. There is no preset mixture adjustment
(1 turn out or 2 turns out) That would be impossible. Every motor is different in so many ways.
With the motor running turn the mixture screw in clockwise until the motor starts to stumble or wants to die.
Back the screw out in 1/4 turn increments, pausing after each 1/4 turn and listening for the RPM of the motor to increase. This increase will be vary small and faint.
Repeat step 2 until you reach the highest idle. Do not keep turning thinking it will help. If you keep turning out the screw than you will have a rich mixture.
(see chart above) If you do not turn the screw out as needed than you will have a lean mixture. (see chart above)
If you have turned out the screw last 1/4 turn and there is no increase in RPM than turn the screw back in 1/4 turn to the last point were you reached the highest rpm. This is the best mixture adjust or at the point were your motor is burning the fuel and air mixture correctly.
Repeat this step with the other carburetor.
I will sometimes do 1and 2 side then 3 and 4 side then do 1 and 2 again over and over. Do not pinch off the crossover tube. Each time you do the steps over and over the motor will run better. One carb will make changes to the other.
Now you will need to re-adjust the idle. (See Idle Adjustment)
Rich (poor gas mileage)
Max RPM at idle from