Yamaha YZ250F(X) Owner's Service Manual page 106

REMOVING THE BALANCER
1. Straighten the lock washer tab.
2. Loosen:
• Nut (primary drive gear) "1"
• Nut (balancer shaft driven gear)
"2"
Place an aluminum plate "a" between
the teeth of the balancer shaft drive
gear "3" and driven gear "4".
3. Remove:
• Balancer shaft "1"
When removing the balancer shaft,
align the center "a" of the balancer
shaft weight along the line connecting
the centers of the crankshaft and bal-
ancer shaft.
CHECKING THE PRIMARY DRIVE
GEAR, BALANCER SHAFT DRIVE
GEAR AND BALANCER SHAFT
DRIVEN GEAR
1. Inspect:
• Primary drive gear "1"
• Balancer shaft drive gear "2"
• Balancer shaft driven gear "3"
→
Wear/damage Replace.
CHECKING THE BALANCER
SHAFT
1. Inspect:
• Balancer shaft
→
Cracks/damage Replace.
INSTALLING THE BALANCER
1. Install:
• Balancer shaft "1"
• Apply the engine oil on the bearing.
• When installing the balancer shaft,
align the center "a" of the balancer
shaft weight along the line connect-
ing the centers of the crankshaft
and balancer shaft.
2. Install:
• Balancer shaft driven gear "1"
Install the balancer shaft driven gear
onto the balancer shaft while aligning
the punch mark "a" on the balancer
shaft driven gear with the lower spline
"b" on the balancer shaft end.
3. Install:
• Balancer shaft drive gear "1"
• Align the punched mark "a" on the
balancer shaft drive gear with the
punched mark "b" on the balancer
shaft driven gear "2".
• Align the punched mark "c" on the
balancer shaft drive gear with the
lower spline "d" on the crankshaft
end.
4-39
BALANCER
4. Install:
• Lock washer "1"
• Nut (balancer shaft driven gear)
"2"
Nut (balancer shaft driv-
en gear):
50 Nm (5.0 m•kg, 36
ft•lb)
• Primary drive gear "3"
• Lock washer "4"
• Nut (primary drive gear) "5"
Nut (primary drive gear):
75 Nm (7.5 m•kg, 54
ft•lb)
• Install the primary drive gear with its
stepped side "a" facing the engine.
• Place an aluminum plate "b" be-
tween the teeth of the balancer
shaft drive gear "6" and driven gear
"7".
5. Bend the lock washer tab.