Removing The Transmission; Checking The Gears; Checking The Bearing; Installing The Transmission - Yamaha YZ250F 2008 Owner's Service Manual

REMOVING THE TRANSMISSION

1. Remove:
• Main axle "1"
• Drive axle "2"
• Shift cam
• Shift fork 3
• Shift fork 2
• Shift fork 1
• Remove assembly with the collar
"3" installed to the crankcase.
• Remove assembly carefully. Note
the position of each part. Pay partic-
ular attention to the location and di-
rection of shift forks.
• Remove the main axle, drive axle,
shift cam and shift fork all together
by tapping lightly on the transmis-
sion drive axle with a soft hammer.

CHECKING THE GEARS

1. Inspect:
• Matching dog "a"
• Gear teeth "b"
• Shift fork groove "c"
→
Wear/damage Replace.
2. Inspect:
• O-ring "1"
→
Damage Replace.
3. Check:
• Gears movement
→
Unsmooth movement
replace.

CHECKING THE BEARING

1. Inspect:
• Bearing "1"
Rotate inner race with a finger.
→
Rough spot/seizure
TRANSMISSION, SHIFT CAM AND SHIFT FORK
CHECKING THE SHIFT FORK,
SHIFT CAM AND SEGMENT
1. Inspect:
• Shift fork "1"
Wear/damage/scratches
place.
2. Inspect:
• Shift cam "1"
• Segment "2"
Wear/damage
3. Check:
• Shift fork movement
Unsmooth operation
shift fork.
For a malfunctioning shift fork, re-
place not only the shift fork itself but
the two gears each adjacent to the
shift fork.

INSTALLING THE TRANSMISSION

1. Install:
• 5th pinion gear (24T) "1"
Repair or
• 3rd pinion gear (20T) "2"
• Collar "3"
• 4th pinion gear (22T) "4"
• 2nd pinion gear (16T) "5"
To main axle "6".
Replace.
Apply the molybdenum disulfide oil
on the inner and end surface of the
→
Re-
→
Replace.
→
Replace
4-62
idler gear and on the inner surface of
the sliding gear, then install.
2. Install:
• 2nd wheel gear (28T) "1"
• 4th wheel gear (27T) "2"
• 3rd wheel gear (29T) "3"
• 5th wheel gear (25T) "4"
• 1st wheel gear (30T) "5"
• O-ring "6"
To drive axle "7".
• Apply the molybdenum disulfide oil
on the inner and end surface of the
idler gear and on the inner surface
of the sliding gear, then install.
• Apply the lithium soap base grease
on the O-ring.
3. Install:
• Washer "1"
• Circlip "2"
• Be sure the circlip sharp-edged cor-
ner "a" is positioned opposite side
to the washer and gear "b".
• Install the circlip with its ends "c"
settled evenly on the spline crests.