2015 YAMAHA YZ250F checking oil

CRANKCASE
5-64
EAS1SM5279DISASSEMBLING THE CRANKCASE
1. Separate:
• Right crankcase
• Left crankcase
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a. Remove the crankcase bolts.
TIP
Loosen each bolt 1/4 of a turn at a time and af-
ter all the bolts are loosened, remove them.
b. Remove the right crankcase “1”.
TIP
• Place the crankcase with its left side down-
ward and split it by inserting a screwdriver tip
into the splitting slit “a” in the crankcase.
• Lift the right crankcase horizontally while light-
ly patting the crankcase splitting slit and the
engine mounting boss using a soft hammer,
and leave the crankshaft and the transmission
with the left crankcase.
ECA33DD041
NOTICE
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 the cases do not
separate, check for a remaining case bolt or
fitting. Do not force.c. Remove the dowel pins and O-ring.
▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲▲EAS1SM5280REMOVING THE CRANKCASE BEARING
1. Remove:
• Bearing “1”
TIP
• Remove the bearing from the crankcase by
pressing its inner race.
• Do not use the removed bearing.
EAS1SM5281CHECKING THE TIMING CHAIN, TIMING
CHAIN GUIDE, OIL STRAINER
1. Check:
• Timing chain
Stiffness  Replace the camshaft sprocket,
timing chain and crankshaft sprocket as a
set.
2. Check:
• Timing chain guide
Damage/wear  Replace
EAS1SM5282CHECKING THE CRANKCASE
1. Wash:
• Crankcase
TIP
• Wash the crankcase in a mild solvent.
• Remove any remaining gasket from the
crankcase mating surface.
2. Check:
• Crankcase
Crack/damage  Replace.
• Oil delivery passages
Obstruction  Blow out with compressed
air.
1
a

CRANKSHAFT ASSEMBLY AND BALANCER SHAFT
5-67
EAS1SM5286REMOVING THE CRANKSHAFT ASSEMBLY
1. Remove:
• Crankshaft assembly “1”
TIP
Remove the crankshaft assembly by using the
crankcase separating tool “2”.
EAS1SM5287CHECKING THE CRANKSHAFT ASSEMBLY
1. Measure:
• Crankshaft runout
Out of specification  Replace the crank-
shaft, bearing or both.
TIP
Turn the crankshaft slowly.2. Measure:
• Big end side clearance D “a”
Out of specification  Replace the big end
bearing, crankshaft pin, or connecting rod.
3. Measure:
• Crankshaft width A “a”
Out of specification  Replace the crank-
shaft.
4. Check:
• Crankshaft sprocket “1”
Damage  Replace the crankshaft.
5. Check:
• Crankshaft journal oil passage
Obstruction  Blow out with compressed
air. Crankcase separating tool
90890-04152
YU-A9642
Runout limit C
0.030 mm (0.0012 in)
2
1
Big end side clearance D
0.150–0.450 mm (0.0059–0.0177
in)
Width A
55.95–56.00 mm (2.203–2.205 in)
1

TRANSMISSION
5-71
EAS1SM5293CHECKING THE SHIFT DRUM ASSEMBLY
1. Check:
• Shift drum groove
Damage/scratches/wear  Replace the
shift drum assembly.
• Shift drum segment “1”
Damage/wear  Replace the shift drum as-
sembly.
EAS1SM5294CHECKING THE TRANSMISSION
1. Measure:
• Main axle runout
(with a centering device and dial gauge “1”)
Out of specification  Replace the main ax-
le.
2. Measure:
• Drive axle runout
(with a centering device and dial gauge “1”)
Out of specification  Replace the drive ax-
le.3. Check:
• Transmission gears
Blue discoloration/pitting/wear  Replace
the defective gear (s).
• Transmission gear dogs
Cracks/damage/rounded edges  Replace
the defective gear (s).
4. Check:
• Transmission gear movement
Rough movement  Replace the defective
gear (s).
EAS1SM5295INSTALLING THE TRANSMISSION
1. Install:
• 5th pinion gear (24T) “1”
• 3rd pinion gear (18T) “2”
• Collar “3”
• 4th pinion gear (18T) “4”
• 2nd pinion gear (16T) “5”
(to the main axle “6”)
TIP
Before installation, apply molybdenum disulfide
oil to the inner and end surface of the idler gear
and to the inner surface of the sliding gear, then
install. Main axle runout limit
0.08 mm (0.0032 in)
Drive axle runout limit
0.08 mm (0.0032 in)
34
2
1
6
5
M

6
COOLING SYSTEM
RADIATOR....................................................................................................... 6-1
HANDLING NOTE ...................................................................................... 6-3
CHECKING THE RADIATOR ..................................................................... 6-3
WATER PUMP.................................................................................................. 6-4
REMOVING THE OIL SEAL ....................................................................... 6-6
CHECKING THE WATER PUMP ............................................................... 6-6
CHECKING THE BEARING....................................................................... 6-6
INSTALLING THE OIL SEAL..................................................................... 6-6
ASSEMBLING THE WATER PUMP........................................................... 6-6

WATER PUMP
6-6
EAS1SM5301REMOVING THE OIL SEAL
TIP
• Remove the oil seal when the coolant level
changes frequently more than usual, coolant
has discolored, or engine oil has become
milky.
• Do not use the removed oil seal.
1. Remove:
• Oil seals “1”
EAS1SM5302CHECKING THE WATER PUMP
1. Check:
• Water pump housing cover
• Impeller shaft
Cracks/damage/wear  Replace.
EAS1SM5303CHECKING THE BEARING
1. Check:
• Bearing
Rotate the inner race with your finger.
Rough spot/seizure  Replace.
EAS1SM5304INSTALLING THE OIL SEAL
1. Install:
• Oil seals “1”
TIP
• Apply the lithium soap base grease on the oil
seal lip.
• Install the oil seal with its manufacture’s
marks or numbers facing the right crankcase
cover “2”.2. Install:
• Bearing “1”
TIP
Install the bearing by pressing its outer race
parallel.
EAS1SM5305ASSEMBLING THE WATER PUMP
1. Install:
• Impeller shaft assembly “1”
• Washer “2”
•Pin “3”
• Gear “4”
• Collar “5”
• Circlip “6”
TIP
• Take care so that the oil seal lip is not dam-
aged or the spring does not slip off its posi-
tion.
• When installing the impeller shaft, apply the
engine oil to the oil seal lip, the bearing, and
the impeller shaft.
1 1
New
1 1New
New
LS
LS
New
1
2
52346
New
E

8
ELECTRICAL SYSTEM
IGNITION SYSTEM.......................................................................................... 8-2
CIRCUIT DIAGRAM ................................................................................... 8-2
TROUBLESHOOTING ............................................................................... 8-4
CHARGING SYSTEM....................................................................................... 8-6
CIRCUIT DIAGRAM ................................................................................... 8-6
TROUBLESHOOTING ............................................................................... 8-8
FUEL INJECTION SYSTEM........................................................................... 8-10
CIRCUIT DIAGRAM ................................................................................. 8-10
YAMAHA DIAGNOSTIC TOOL ................................................................ 8-12
TROUBLESHOOTING DETAILS ............................................................. 8-13
FUEL PUMP SYSTEM.................................................................................... 8-32
CIRCUIT DIAGRAM ................................................................................. 8-32
TROUBLESHOOTING ............................................................................. 8-34
ELECTRICAL COMPONENTS....................................................................... 8-36
CHECKING THE SWITCHES .................................................................. 8-38
CHECKING THE IGNITION SPARK GAP................................................ 8-41
CHECKING THE SPARK PLUG CAP ...................................................... 8-41
CHECKING THE IGNITION COIL ............................................................ 8-41
CHECKING THE CRANKSHAFT POSITION SENSOR........................... 8-42
CHECKING THE ECU .............................................................................. 8-43
CHECKING THE STATOR COIL ............................................................. 8-43
CHECKING THE RECTIFIER/REGULATOR ........................................... 8-43
CHECKING THE COOLANT TEMPERATURE SENSOR........................ 8-44
CHECKING THE THROTTLE POSITION SENSOR ................................ 8-44
CHECKING THE THROTTLE POSITION SENSOR
INPUT VOLTAGE .................................................................................... 8-45
CHECKING THE INTAKE AIR PRESSURE SENSOR ............................ 8-46
CHECKING THE INTAKE AIR TEMPERATURE SENSOR ..................... 8-46
CHECKING THE NEUTRAL SWITCH ..................................................... 8-46
CHECKING THE FUEL INJECTOR ......................................................... 8-47

IGNITION SYSTEM
8-4
EAS1SM5324TROUBLESHOOTING
The ignition system fails to operate (no spark or intermittent spark).
TIP
Before troubleshooting, remove the following part(s):
1. Side cover (left/right)
2. Seat
3. Fuel tank
4. Air scoop (left/right)
5. Air filter case cover
1. Check the ignition system wire har-
ness connections.NG 
Reconnect.
OK 
2. Check the spark plug.
Refer to “CHECKING THE SPARK
PLUG” on page 3-35.NG 
Correct or replace the spark plug.
OK 
3. Check the ignition spark gap.
Refer to “CHECKING THE IGNI-
TION SPARK GAP” on page 8-41.OK 
The ignition system circuit is OK.
NG 
4. Check the ignition coil.
Refer to “CHECKING THE IGNI-
TION COIL” on page 8-41.NG 
Replace the ignition coil.
OK 
5. Check the engine stop switch.
Refer to “CHECKING THE
SWITCHES” on page 8-38.NG 
Replace the engine stop switch.
OK 
6. Check the crankshaft position sen-
sor.
Refer to “CHECKING THE CRANK-
SHAFT POSITION SENSOR” on
page 8-42.NG 
Replace the crankshaft position sensor.
OK 
7. Check the stator coil.
Refer to “CHECKING THE STA-
TOR COIL” on page 8-43.NG 
Replace the stator coil.
OK 

CHARGING SYSTEM
8-8
EAS1SM5326TROUBLESHOOTING
The condenser is not being charged.
TIP
Before troubleshooting, remove the following part (s):
1. Seat
2. Air scoop (left)
1. Check the entire charging system’s
wiring.NG 
Reconnect.
OK 
2. Check the rectifier/regulator.
Refer to “CHECKING THE RECTI-
FIER/REGULATOR” on page 8-43.NG 
Replace the rectifier/regulator.
OK 
3. Check the stator coil.
Refer to “CHECKING THE STA-
TOR COIL” on page 8-43.NG 
Replace the stator coil.
OK 
4. Check the charging system wire
harness.
Refer to “CIRCUIT DIAGRAM” on
page 8-6.NG 
Repair or replace the wire harness.
OK 
Replace the condenser.