light YAMAHA WR 250F 2001 Owner's Guide

4 - 25
ENGCAMSHAFTS
Timing chain tensioner
1. Check:
lWhile pressing the tensioner rod lightly
with fingers, use a thin screwdriver 1
and wind the tensioner rod up fully
clockwise.
lWhen releasing the screwdriver by
pressing lightly with fingers, make sure
that the tensioner rod will come out
smoothly.
lIf not, replace the tensioner assembly.
ASSEMBLY AND INSTALLATION
Camshaft
1. Install:
lExhaust camshaft 1
lIntake camshaft 2
Installation steps:
lTurn the crankshaft counterclockwise with
a wrench.
NOTE:
Squeezing the decompression lever allows
the crankshaft to be turned easily.
lAlign the T.D.C. mark a on the rotor with
the align mark b on the crankcase cover
when piston is at T.D.C. on compression
stroke.
lFit the timing chain 3 onto both camshaft
sprockets and install the camshafts on the
cylinder head.
NOTE:
The camshafts should be installed onto the
cylinder head so that the punch mark c on
the exhaust camshaft and the punch mark
d on the intake camshaft must align with
the cylinder head surface, as shown in the
illustration.

4 - 26
ENGCAMSHAFTS
CAUTION:
Do not turn the crankshaft during the
camshaft installation. Damage or
improper valve timing will result.
lInstall the clips, camshaft caps 4 and
bolts (camshaft cap) 5.
T R..
Bolt (camshaft cap):
10 Nm (1.0 m • kg, 7.2 ft • lb)
NOTE:
lBefore removing the clips, cover the cylin-
der head with a clean rag to prevent the
clips from into the cylinder head cavity.
lApply the engine oil on the thread and con-
tact surface of the bolts (camshaft cap).
lTighten the bolts (camshaft cap) 5 in a
crisscross pattern.
CAUTION:
The bolts (camshaft cap) must be tight-
ened evenly or damage to the cylinder
head, camshaft caps and camshaft will
result.
2. Install:
lTiming chain tensioner
Installation steps:
lWhile pressing the tensioner rod lightly
with fingers, use a thin screwdriver and
wind the tensioner rod up fully clockwise.
lWith the rod fully wound and the chain
tensioner UP mark a facing upward,
install the gasket 1 and the timing chain
tensioner 2, and tighten the bolt 3 to the
specified torque.
T R..
Bolt (timing chain tensioner):
10 Nm (1.0 m • kg, 7.2 ft • lb)

4 - 38
ENGVALVES AND VALVE SPRINGS
9. Lap:
lValve face
lValve seat
NOTE:
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and
valve face should be lapped.
Lapping steps:
lApply a coarse lapping compound to the
valve face.
CAUTION:
Do not let the compound enter the gap
between the valve stem and the guide.
lApply molybdenum disulfide oil to the
valve stem.
lInstall the valve into the cylinder head.
lTurn the valve until the valve face and
valve seat are evenly polished, then clean
off all of the compound.
NOTE:
For best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands.
lApply a fine lapping compound to the
valve face and repeat the above steps.
NOTE:
After every lapping operation be sure to
clean off all of the compound from the valve
face and valve seat.
lApply Mechanic’s blueing dye (Dykem) to
the valve face.
lInstall the valve into the cylinder head.
lPress the valve through the valve guide
and onto the valve seat to make a clear
pattern.
lMeasure the valve seat width again. If the
valve seat width is out of specification,
reface and relap the valve seat.

4 - 41
ENGVALVES AND VALVE SPRINGS
3. Install:
lValve cotter
NOTE:
While compressing the valve spring with a
valve spring compressor 1 install the valve
cotters.
4. To secure the valve cotters onto the
valve stem, lightly tap the valve tip with a
piece of wood.
CAUTION:
Hitting the valve tip with excessive force
could damage the valve.
Valve spring compressor:
YM-04019/90890-04019
5. Install:
lAdjusting pad 1
lValve lifter 2
NOTE:
lApply the molybdenum disulfied oil on the
valve stem end.
lApply the engine oil on the valve lifters.
lValve lifter must turn smoothly when rotated
with a finger.
lBe careful to reinstall valve lifters and pads
in their original place.

4 - 90
ENGCRANKCASE AND CRANKSHAFT
REMOVAL POINTS
Crankcase
1. Separate:
lRight crankcase
lLeft crankcase
Separation steps:
lRemove the crankcase bolts 1, hose
guide 2 and clutch cable holder 3.
NOTE:
Loosen each bolt 1/4 of a turn at a time and
after all the bolts are loosened, remove
them.
lRemove the right crankcase 4.
NOTE:
lPlace the crankcase with its left side
downward and split it by inserting a screw-
driver tip into the splitting slit a in the
crankcase.
lLift the right crankcase horizontally while
lightly patting the case splitting slit and
engine mounting boss using a soft ham-
mer, and leave the crankshaft and trans-
mission with the left crankcase.
CAUTION:
Use soft hammer to tap on the case half.
Tap only on reinforced portions of case.
Do not tap on gasket mating surface.
Work slowly and carefully. Make sure the
case halves separate evenly. If one end
“hangs up”, take pressure off the push
screw, realign, and start over. If the
cases do not separate, check for a
remaining case screw or fitting. Do not
force.
lRemove the dowel pins and O-ring.
a
4

4 - 94
ENGCRANKCASE AND CRANKSHAFT
2. Check:
lShifter operation
lTransmission operation
Unsmooth operation ® Repair.
3. Install:
lOil strainer 1
lBolt (oil strainer) 2
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
4. Apply:
lSealant
On the right crankcase 1.
NOTE:
Clean the contacting surface of left and right
crankcase before applying the sealant.
5. Install:
lDowel pin 1
lO-ring 2
lRight crankcase
To left crankcase.
NOTE:
lFit the right crankcase onto the left crank-
case. Tap lightly on the case with soft ham-
mer.
lWhen installing the crankcase, the connect-
ing rod should be positioned at TDC (top
dead center).
Quick gasket®:
ACC-QUICK-GS-KT
YAMAHA Bond No. 1215:
90890-85505

4 - 97
ENGTRANSMISSION, SHIFT CAM AND SHIFT FORK
EC4H3000
REMOVAL POINTS
EC4H3230
Transmission
1. Remove:
lMain axle 1
lDrive axle 2
lShift cam
lShift fork 3
lShift fork 2
lShift fork 1
NOTE:
lRemove assembly with the collar 3 installed
to the crankcase.
lRemove assembly carefully. Note the posi-
tion of each part. Pay particular attention to
the location and direction of shift forks.
lRemove the main axle, drive axle, shift cam
and shift fork all together by tapping lightly
on the transmission drive axle with a soft
hammer.
EC4H4000
INSPECTION
EC4H4200
Gears
1. Inspect:
lMatching dog a
lGear teeth b
lShift fork groove c
Wear/damage ® Replace.
2. Inspect:
lO-ring 1
Damage ® Replace.
3. Check:
lGears movement
Unsmooth movement ® Repair or
replace.
EC4H4600
Bearing
1. Inspect:
lBearing 1
Rotate inner race with a finger.
Rough spot/seizure ® Replace.

5 - 19
CHASFRONT BRAKE AND REAR BRAKE
2. Install:
lCopper washer 1
lUnion bolt 2
WARNING
Always use new copper washers.
CAUTION:
Install the brake hose so that its pipe por-
tion a directs as show and lightly touches
the projection b on the brake caliper.
T R..30 Nm (3.0 m · kg, 22 ft · lb)
3. Install:
lBrake hose holder 1
lBrake caliper 2
lBolt (brake caliper) 3
NOTE:
Fit the brake hose holder cut a over the pro-
jection b on the front fork and clamp the brake
hose.
4. Tighten:
lPad pin 4
5. Install:
lPad pin plug 5
Rear brake caliper
1. Install:
lPad support 1
lBrake pad 2
lPad pin 3
NOTE:
lInstall the brake pads with their projections
a into the brake caliper recesses b.
lTemporarily tighten the pad pin at this point.
T R..23 Nm (2.3 m · kg, 17 ft · lb)
T R..18 Nm (1.8 m · kg, 13 ft · lb)
T R..3 Nm (0.3 m · kg, 2.2 ft · lb)

5 - 28
CHASFRONT FORK
EC550000
FRONT FORK
Extent of removal:1 Front fork removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removalFRONT FORK REMOVAL
Hold the machine by placing the
suitable stand under the engine.
WARNING
Support the machine securely so there is nodanger of it falling over.
Front wheel Refer to “FRONT WHEEL AND REAR
WHEEL” section.
Front brake caliper Refer to “FRONT BRAKE AND REAR
BRAKE” section.
Headlight
Handlebar Refer to “HANDLEBAR” section.
1 Protector 1
2 Brake hose holder 2
3 Pinch bolt (upper bracket) 2 Only loosening.
4 Cap bolt 1Loosen when disassembling the front fork.
5 Pinch bolt (lower bracket) 2 Only loosening.
6 Front fork 1
1

5 - 41
CHAS
EC5B0000
HANDLEBAR
Extent of removal:1 Handlebar removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removalHANDLEBAR REMOVAL
Headlight
1 Decompression cable 1 Disconnect at the lever side.
2 Decompression lever holder 1
3 Clutch cable 1 Disconnect at the lever side.
4 Clutch lever holder 1
5 Engine stop switch 1
6 Light switch 1
7 Brake master cylinder 1 Refer to “REMOVAL POINTS”.
8 Throttle cable cap 1
9 Throttle cable #2 (pushed) 1 Disconnect at the throttle side.
10 Throttle cable #1 (pulled) 1 Disconnect at the throttle side.
11 Right grip 1 Refer to “REMOVAL POINTS”.
12 Tube guide 1
13 Collar 1
14 Left grip 1 Refer to “REMOVAL POINTS”.
15 Handlebar upper holder 2
16 Handlebar 1
1
HANDLEBAR