2008 YAMAHA WR 250F check engine

5-62
CRANKCASE AND CRANKSHAFT
5. Install:• Dowel pin "1"
• O-ring "2"
• Right crankcaseTo left crankcase.
• Apply the lithium soap base grease
on the O-ring.
• Fit the right crankcase onto the left crankcase. Tap lightly on the case
with soft hammer.
• When installing the crankcase, the connecting rod should be posi-
tioned at TDC (top dead center).
6. Tighten:
• Hose guide "1"
• Clutch cable holder "2"
• Bolt (crankcase) "3"
Tighten the crankcase tightening
bolts in stage, using a crisscross pat-
tern.
7. Install:• Oil delivery pipe 2 "1"
• O-ring "2"
• Bolt (oil delivery pipe 2) "3"
Apply the lithium soap base grease
on the Orings.
8. Install:• Timing chain "1"
• Timing chain guide (intake side)
"2"
• Bolt (timing chain guide) "3"
9. Remove: • Sealant
Forced out on the cylinder mating
surface.
10. Apply:
• Engine oilTo the crank pin, bearing and oil
delivery hole.
11. Check: • Crankshaft and transmission op-eration.
Unsmooth operation →Repair.
Bolt (crankcase):
12 Nm (1.2 m•kg, 8.7
ft•lb)
Bolt (oil delivery pipe 2): 10 Nm (1.0 m•kg, 7.2
ft•lb)
Bolt (timing chain guide):10 Nm (1.0 m•kg, 7.2
ft•lb)

5-65
TRANSMISSION, SHIFT CAM AND SHIFT FORK
4. Install:•Collar "1"
• Apply the lithium soap base grease on the oil seal lip.
• When installing the collar into the crankcase, pay careful attention to
the crankcase oil seal lip.
5. Install:• Shift fork 1 (L) "1"
• Shift fork 2 (C) "2"
• Shift fork 3 (R) "3"
• Shift cam "4"
To main axle and drive axle.
• Apply the molybdenum disulfide oil on the shift fork grooves.
• Mesh the shift fork #1 (L) with the
4th wheel gear "5" and #3 (R) with
the 5th wheel gear "7" on the drive
axle.
• Mesh the shift fork #2 (C) with the 3rd pinion gear "6" on the main ax-
le.
6. Install:
• Transmission assembly "1"To left crankcase "2".
Apply the engine oil on the bearings
and guide bars.
7. Check:• Shifter operation
• Transmission operation
Unsmooth operation →Repair.

6-25
HANDLEBAR
5. Install:• Right grip "1"
•Collar "2"Apply the adhesive on the tube
guide "3".
• Before applying the adhesive, wipe off grease or oil on the tube guide
surface "a" with a lacquer thinner.
• Install the grip to the tube guide so that the grip match mark "b" and
tube guide slot "c" form the angle as
shown.
6. Install:• Grip cap cover "1"
• Throttle grip "2"
Apply the lithium soap base grease
on the throttle grip sliding surface.
7. Install:
• Throttle cables "1"To tube guide "2".
Apply the lithium soap base grease
on the throttle cable end and tube
guide cable winding portion.
8. Install:
• Throttle cable cap "1"
• Screw (throttle cable cap) "2"
After tightening the screws, check
that the throttle grip "3" moves
smoothly. If it does not, retighten
the bolts for adjustment.
9. Install:• Grip cap cover "1"
• Cover (throttle cable cap) "2"
10. Install: • Start switch "1"
• Brake master cylinder "2"
• Brake master cylinder bracket "3"
• Bolt (brake master cylinder brack-
et) "4"
•Clamp "5"
• The start switch and brake master
cylinder bracket should be installed
according to the dimensions
shown.
• Install the bracket so that the arrow
mark "a" faces upward.
• First tighten the bolt on the upper side of the brake master cylinder
bracket, and then tighten the bolt on
the lower side.
11. Install:
• Engine stop switch "1"
• Clutch lever holder "2"
• Bolt (clutch lever holder) "3"
• Hot starter lever holder "4"
• Bolt (hot starter lever holder) "5"
• Clamp "6"
• The engine stop switch, clutch lever holder and clamp should be in-
stalled according to the dimensions
shown.
• Pass the engine stop switch lead in
the middle of the clutch lever hold-
er.
Screw (throttle cable
cap): 4 Nm (0.4 m•kg, 2.9
ft•lb)
Bolt (brake master cylin-
der bracket): 9 Nm (0.9 m•kg, 6.5
ft•lb)
Bolt (clutch lever holder): 4 Nm (0.4 m•kg, 2.9
ft•lb)
Bolt (hot starter lever
holder): 4 Nm (0.4 m•kg, 2.9
ft•lb)

6-36
REAR SHOCK ABSORBER
REAR SHOCK ABSORBER
REMOVING THE REAR SHOCK ABSORBEROrder Part name Q'ty Remarks Hold the machine by placing the suitable stand
under the engine. Refer to "HANDLING NOTE".
Seat and side cover Refer to "REMOVING THE SEAT, FUEL
TANK AND SIDE COVERS" section in the
CHAPTER 3.
Silencer Refer to "REMOVING THE EXHAUST PIPE
AND SILENCER" section in the CHAPTER 3.
Drain the coolant. Refer to "CHANGING
THE COOLANT" sec-
tion in the CHAPTER 3.
Catch tank breather hose Disconnect at the catch tank side.
Catch tank hose Disconnect at the catch tank side.
Air induction hose (air cut-off va lve-air filter case)Disconnect at the air filter case side.
Cylinder head breather hose Disconnect at the air filter case side.
Battery Refer to "CHECKING AND CHARGING THE
BATTERY" section in the CHAPTER 3.
Disconnect the starter relay coupler.
Starter motor lead Disconnect at the starter relay side.
1 Locking tie 4

7-3
IGNITION SYSTEM
IGNITION SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to ignition system failure
and for checking the spark plug which will not spark.
*1 marked: Refer to "CHECKING TH E FUSE" section in the CHAPTER 3.
*2 marked: Refer to "CHECKING AND CHARGIN G THE BATTERY" section in the CHAPTER 3.
*3 marked: Only when the ignition checker is used.
• Remove the following parts before inspection.
1. Seat
2. Fuel tank
• Use the following special tools in this inspection.
*1 Check fuse. No good→Replace fuse and check wire harness.
OK ↓
*2 Check battery. No good→Recharge or replace.
OK ↓
Spark gap test Spark→ *3 Clean or replace spark plug.
No spark ↓
Check entire ignition system for connection.
(couplers, leads and ignition coil) No good
→
Repair or replace.
OK ↓
Check engine stop switch. No good→Replace.
OK ↓
Check main switch. No good→Replace.
OK ↓
Check ignition coil. (primary coil and secondary
coil) No good
→
Replace.
OK ↓
Check AC magneto. (pickup coil) No good→Replace.
OK ↓
Check neutral switch. No good→Repair or replace.
OK ↓
Replace CDI unit.
Dynamic spark tester: YM-34487
Ignition checker: 90890-06754
Pocket tester: YU-3112-C/90890-03112

7-4
IGNITION SYSTEM
SPARK GAP TEST
1. Disconnect the ignition coil from spark plug.
2. Remove the ignition coil cap.
3. Connect the dynamic spark tester "1" (ignition ch ecker "2") as
shown.
• Ignition coil "3"
• Spark plug "4"
A. For USA and CDN
B. Except for USA and CDN
4. Kick the kickstarter crank.
5. Check the ignition spark gap.
6. Start engine, and increase spark gap until misfire occurs. (for USA
and CDN only)
CHECKING THE COUPLERS,
LEADS AND IGNITION COIL
CONNECTION
1. Check: • Couplers and leads connection
Rust/dust/looseness/short-circuit
→ Repair or replace.
• Ignition coil and spark plug as
they are fitted
Push in the ignition coil until it
closely contacts the spark plug
hole in the cylinder head cover.
CHECKING THE ENGINE STOP
SWITCH
1. Inspect: • Engine stop switch conduction Not conductive while it is pushed
→
Replace.
Conductive while it is freed →Re-
place.
Set the tester selection position to " Ω
× 1".
2. Inspect: • Rubber part "a"
Tears/damage → Replace.
CHECKING THE MAIN SWITCH
1. Inspect: • Main switch conduction
Not conductive while the main switch
is moved to "ON" →Replace.
Conductive while the main switch is
moved to "OFF" →Replace.
Set the tester selection position to
"Ω×1".
2. Inspect:
• Main switch indicator lightUse 12 V battery.
Indicator light does not come on →
Replace.
3. Inspect:
• Rubber part "a"Tears/damage →Replace.
CHECKING THE IGNITION COIL
1. Remove the ignition coil cap.
2. Inspect: • Primary coil resistance
Out of specification →Replace.
3. Inspect: • Secondary coil resistanceOut of specification →Replace.
Minimum spark gap:
6.0 mm (0.24 in)
Tester (+) lead →Black lead "1"
Tester (-) lead →Black lead "2"Result
Conductive (while the
engine stop switch is
pushed)
Tester (+) lead →Red lead "1"
Tester (-) lead →Brown lead "2"
Result Conductive (while the
main switch is moved
to "ON")
Battery (+) lead →Red/Black lead
"1"
Battery (-) lead →Black lead "2"
Tester (+) lead →Orange lead "1"
Tester (-) lead →Black lead "2"
Primary
coil resis-
tance Tester se-
lector posi-
tion
0.08–0.10
Ω at 20 °C (68 °F) Ω × 1
Tester (+) lead →Orange lead "1"
Tester (-) lead →Spark plug termi-
nal "2"

7-5
ELECTRIC STARTING SYSTEM
4. Inspect:• Sealed portion of ignition coil "a"
• Spark plug terminal pin "b"
• Threaded portion of spark plug "c"Wear →Replace.
CHECKING THE AC MAGNETO
1. Inspect: • Pickup coil resistanceOut of specification →Replace. CHECKING THE NEUTRAL
SWITCH
1. Inspect:
• Neutral switch conduction
Not conductive while it is in neutral →
Replace.
Conductive while it is engaged →Re-
place.Set the tester selection position to " Ω
× 1".
CHECKING THE CDI UNIT
Check all electrical components. If no
fault is found, replace the CDI unit.
Then check the electrical compo-
nents again.
ELECTRIC STARTING
SYSTEM
STARTING CIRCUIT CUT-OFF
SYSTEM OPERATION
If the main switch is set to "ON", the
starter motor can only operate if at
least one of the following conditions is
met:
• The transmission is in neutral (the neutral switch is closed).
• The clutch lever is pulled to the han- dlebar (the clutch switch is closed).
The starting circuit cut-off relay pre-
vents the starter motor from operating
when neither of these conditions has
been met. In this instance, the start-
ing circuit cut-off relay is open so cur-
rent cannot reach the starter motor.
When at least one of the above con-
ditions has been met the starting cir-
cuit cut-off relay is closed and the
engine can be started by pressing the
start switch.
WHEN THE TRANSMISSION IS IN
NEUTRAL
WHEN THE CLUTCH LEVER IS
PULLED TO THE HANDLEBAR 1. Battery
2. Main fuse
3. Main switch
4. Starting circuit cut-off relay
5. Start switch
6. Diode
7. Clutch switch
8. Neutral switch
9. Starter relay
10. Starter motor
Secondary
coil resis- tance Tester se-
lector posi- tion
4.6–6.8
k Ωat 20 °C
(68 °F) k
Ω × 1
Tester (+) lead →Red lead "1"
Tester (-) lead →White lead "2"
Pickup coil resistance Tester se-
lector posi- tion
248–372 Ω
at 20 °C (68
°F) Ω × 100
Tester (+) lead
→Sky blue lead "1"
Tester (-) lead →Ground "2"
Result Conductive (while gear
is in neutral)

7-14
CHARGING SYSTEM
CHECKING THE COUPLERS AND
LEADS CONNECTION
1. Check:• Couplers and leads connection
Rust/dust/looseness/short-circuit
→ Repair or replace.
CHECKING THE CHARGING
VOLTAGE
1. Start the engine.
2. Inspect: • Charging voltageOut of specification →If no failure
is found in checking the source
coil resistance, replace the rectifi-
er/regulator.
3. Inspect: • Charging coil resistanceOut of specification →Replace.
Tester (+) lead
→Red lead "1"
Tester (-) lead →Black lead "2"
Charging voltage Tester se-
lector posi- tion
14.0–15.0 V at 5,000 r/ min DCV-20
Tester (+) lead →White lead "1"
Tester (-) lead →Ground "2"
Charging
coil resis- tance Tester se-
lector posi- tion
0.288–0.432 Ω at 20 °C
(68 °F) Ω × 1