ENGINE
10-5
EAM30601
ROAD CONDITION AND EXAMPLES OF CARBURETOR SETTING
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.
EAM30600
SPECIFICATIONS OF JET NEEDLE
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 30
C
(86
F)
(Summer)
Under 10
C
(50
F)
(Winter)
15–25
C
(59–77
F)
(Spring,
Autumn)
Over 30
C
(86
F)
(Summer)
Main jet
#440
#430
#420
#460
#450
#440
Jet needle
6BFY44-74-3 6BFY43-74-3 6BFY44-74-2 6BFY43-74-4 6BFY44-74-3 6BFY43-74-3
Pilot jet
#42.5
#40
#37.5
#45
#42.5
#40
Pilot air
screw
2-1/4
2-1/4
2-1/4
2-1/4
2-1/4
2-1/4
Diameter of straight portion
ø2.72 mm
(0.1071 in)
ø2.73 mm
(0.1075 in)
ø2.74 mm
(0.1079 in)
ø2.75 mm
(0.1083 in)
ø2.76 mm
(0.1087 in)
Rich
1 richer
6BFY43-72-4
6BFY43-73-4
6BFY43-74-4
6BFY43-75-4
6BFY43-76-4
0.5 richer
6BFY44-72-3
6BFY44-73-3
6BFY44-74-3
6BFY44-75-3
6BFY44-76-3
6BFY42-72-4
6BFY42-73-4
6BFY42-74-4
6BFY42-75-4
6BFY42-76-4
STD
6BFY43-72-3
6BFY43-73-3
6BFY43-74-3
6BFY43-75-3
6BFY43-76-3
0.5 leaner
6BFY44-72-2
6BFY44-73-2
6BFY44-74-2
6BFY44-75-2
6BFY44-76-2
6BFY42-72-3
6BFY42-73-3
6BFY42-74-3
6BFY42-75-3
6BFY42-76-3
Lean
1 leaner
6BFY43-72-2
6BFY43-73-2
6BFY43-74-2
6BFY43-75-2
6BFY43-76-2
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
Summary of Contents for YZ125X 2022
Page 5: ...EAM20162 YAMAHA MOTOR CORPORATION U S A YZ MOTORCYCLE LIMITED WARRANTY ...
Page 8: ......
Page 10: ......
Page 38: ...MOTORCYCLE CARE AND STORAGE 1 26 ...
Page 54: ...CABLE ROUTING DIAGRAM 2 15 EAM20152 CABLE ROUTING DIAGRAM Frame and engine left side view ...
Page 56: ...CABLE ROUTING DIAGRAM 2 17 Frame and engine right side view ...
Page 58: ...CABLE ROUTING DIAGRAM 2 19 Handlebar front view 0 in 0 mm 0 mm 0 in ...
Page 60: ...CABLE ROUTING DIAGRAM 2 21 Rear brake right side view ...
Page 62: ...CABLE ROUTING DIAGRAM 2 23 ...
Page 90: ...ELECTRICAL SYSTEM 3 26 ...
Page 158: ...CHAIN DRIVE 4 66 ...
Page 202: ...CRANKSHAFT 5 42 seal lip 4 1 2 3 M ...
Page 226: ...CARBURETOR 7 11 ...
Page 231: ...ELECTRICAL COMPONENTS 8 4 EAM30289 CHECKING THE SWITCHES 1 1 Engine stop switch ...
Page 236: ...ELECTRICAL COMPONENTS 8 9 ...
Page 250: ...TROUBLESHOOTING 9 13 ...
Page 268: ......