Yamaha YZ125X 2023, Owner'S Manual

Page: 131 / 146

ENGINE
8-6
EAM30601
ROAD CONDITION AND EXAMPLES OF CARBURETOR SETTING
A. Except for AUS/NZL
B. For AUS/NZL
TIP
Optimum pilot air screw setting can be obtained by adding the ex-factory number of the same screw
back-out turns to any required value provided in the chart. For example, if the ex-factory number is “1”,
add “1” to the value chosen in the chart.
EAM30602
EXAMPLES OF CARBURETOR SETTING DEPENDING ON SYMPTOM
General condition Sandy condition
Under 10

C
(50

F)
(Winter)
15–25  C
(59–77  F)
(Spring,
Autumn)
Over 25

C
(77

F)
(Summer)
Under 10

C
(50

F)
(Winter)
15–25  C
(59–77  F)
(Spring,
Autumn)
Over 25

C
(77

F)
(Summer)
Main jet
A #162 #160 #158 #168 #165 #162
B #165 #162 #160 #170 #168 #165
Jet needle
A NYDF-3 NYCF-2 NYDF-2 NYCF-3 NYDF-3 NYCF-2
B NYDE-2 NYEE-2 NYDE-1 NYEE-3 NYDE-2 NYEE-2
Pilot jet
A #68 #65 #62 #70 #68 #65
B #62 #60 #58 #65 #62 #60
Pilot air
screw
A 0 0 0 0 0 0
B 0 0 0 0 0 0
Symptom Setting Checking
•
At full throttle
Stall at high speeds
*Hard breathing
Shearing noise
Whitish spark plug

Lean mixture
Increase main jet calibration no.
(Gradually)
•
Discoloration of spark plug

If tan color, it is in good condition.
•
If cannot be corrected:
Clogged float valve seat
Clogged fuel hose
Clogged fuel cock
•
At full throttle
Speed pick-up stops
Slow speed pick-up
Slow response
Sooty spark plug

Rich mixture
Decrease main jet calibration no.
(Gradually)
*In case of racing slight enrichment of
mixture reduces engine trouble.
•
Discoloration of spark plug

If tan color, it is in good condition.
•
If cannot be corrected:
Clogged air filter
Fuel overflow from carburetor
Clogged main air passage or
clogged filter