Yamaha YZ250F(X) Owner's Service Manual page 61

CHECKING THE DRIVE CHAIN
1. Measure:
• Drive chain length (15 links) "a"
→
Out of specification
Drive chain length (15
links):
<Limit>: 242.9 mm
(9.563 in)
• While measuring the drive chain
length, push down on the drive
chain to increase its tension.
• Measure the length between drive
chain roller "1" and "16" as shown.
• Perform this measurement at two or
three different places.
2. Remove:
• Master link clip
• Joint "1"
• Drive chain "2"
3. Clean:
• Drive chain
Place it in kerosene, and brush off
as much dirt as possible. Then re-
move the drive chain from the ker-
osene and dry the drive chain.
4. Check:
• Drive chain stiffness "a"
Clean and oil the drive chain and
hold as illustrated.
→
Stiff
5. Install:
Replace. • Drive chain "1"
• Joint "2"
• Master link clip "3"
Be sure to install the master link
clip to the direction as shown.
a. Turning direction
6. Lubricate:
• Drive chain
Drive chain lubricant:
ADJUSTING THE DRIVE CHAIN
SLACK
1. Elevate the rear wheel by placing
the suitable stand under the en-
gine.
2. Check:
• Drive chain slack "a"
Above the seal guard installation
bolt.
Out of specification
Drive chain slack:
Before checking and/or adjusting, ro-
tate the rear wheel through several
revolutions and check the slack sev-
eral times to find the tightest point.
Check and/or adjust the drive chain
slack with the rear wheel in this "tight
Replace the drive chain.
SAE 10W-30 motor oil
or suitable chain lubri-
cants
→
Adjust.
48–58 mm (1.9–2.3 in)
3-17
CHASSIS
chain" position.
3. Adjust:
• Drive chain slack
Drive chain slack adjustment
steps:
a. Loosen the axle nut "1" and lock-
nuts "2".
b. Adjust the drive chain slack by
turning the adjusters "3".
→
To tighten Turn the adjuster "3"
counterclockwise.
→
To loosen Turn the adjuster "3"
clockwise and push wheel for-
ward.
c. Turn each adjuster exactly the
same amount to maintain correct
axle alignment. (There are marks
"a" on each side of the drive chain
puller alignment.)
Turn the adjuster so that the drive
chain is in line with the sprocket, as
viewed from the rear.
Too small drive chain slack will
overload the engine and other vital
parts; keep the slack within the
specified limits.
d. Tighten the axle nut while pushing
down the drive chain.
Axle nut:
125 Nm (12.5 m•kg, 90
ft•lb)
e. Tighten the locknuts.
Locknut:
19 Nm (1.9 m•kg, 13
ft•lb)