Pilot Jet Adjustment; Jet Needle Adjustment - Yamaha YZ125 2022 Owner's Service Manual

EAM30596

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 can-
not be made by the pilot air screw alone.
A larger size jet results in a richer mixture at low
speeds, and a smaller size in a leaner mixture.
Standard pilot jet
EAM30597

JET NEEDLE ADJUSTMENT

On the carburetors used in the YZ125 the main
nozzle is a non disassembly type, so it can not
be replaced. Therefore, carburetor setting re-
quires the change of the jet needle.
1. The jet needle setting parts, having the same
taper angle, are available in different straight
portion diameters and in different taper start-
ing positions.
Standard jet needle
#75
A. Difference in straight portion diameter
B. Difference in taper starting position
a. Diameter of the straight portion
b. Taper starting position
c. Rich
d. Lean
2. Effects of changing the jet needle (reference)
• Diameter of straight portion
NYDF
Changing the diameter of the straight portion
adjusts the air-fuel mixture when the throttle
is 1/8 to 1/4 open.
• Taper starting position
Changing the taper starting position produc-
es the same effect as changing the clip posi-
tion by 0.5 groove.
Example:
In case of being 0.5 groove leaner in relation
to NYDF-3rd groove, choose NYEF-3rd
groove.
10-3
ENGINE
NYDD
NYDE
NYDF
NYDG
NYDH
NYFF
NYCF
NYDF
NYEF