Yamaha YZ125(W)/W1 Owner's Service Manual page 520

SETTING
EC716001
Pilot air screw adjustment
The richness of air-fuel mixture with full closed to
1/4 throttle can be set by turning the pilot air
screw 1.
Turning in the pilot air screw will enrich the mix-
ture at low speeds, and turning out it will lean out
the mixture.
Standard pilot air
screw position
EC71R010
Pilot jet adjustment
The richness of air - fuel mixture with the throttle
fully closed to 1/2 open can be set by turning the
pilot jet 1.
It is changed when adjustment cannot be made
by the pilot air screw alone.
Standard pilot jet
*For EUROPE
7-4
TUN
2-1/4 turns out
#40
*#45