engine YAMAHA WR 250F 2015 User Guide

IMPORTANT INFORMATION
1-10
EAS2GB2024GASKETS, OIL SEALS AND O-RINGS
1. When overhauling the engine, replace all
gaskets and O-rings. All gasket surfaces, oil
seal lips, and O-rings must be cleaned so
that there may be no dust on them.
2. During assembly, always apply proper oil to
bearings and proper grease to oil seal lips
before installation.
EAS2GB2025LOCK WASHERS/PLATES AND COTTER
PINS
After removal, replace lock washers/plates “1”
and cotter pins with new ones. After the bolt or
nut has been tightened to specification, firmly
bend the lock tabs along a flat of the bolt or nut.
EAS2GB2026BEARINGS AND OIL SEALS
Install bearings “1” and oil seals “2” with their
manufacturer’s marks or size symbols facing
outward. During installation of an oil seal, make
sure that its main lip faces the oil chamber (the
target to be sealed). Before installation, always
apply a light coat of grease to the oil seal lip.
ECA
NOTICE
Do not spin the bearing with compressed air
because this will damage the bearing sur-
faces.
EAS2GB2027CIRCLIPS
When assembling parts, always use new cir-
clips. During installation of a circlip, make sure
that the edge “2” of the circlip “1” is positioned
opposite to the force “3” that the circlip re-
ceives. Install the circlip with its end aligned
with the center of the spline, without opening
the circlip more than necessary.
1. Oil
2. Lip
3. Spring
4. Grease

BASIC SERVICE INFORMATION
1-11
EAS2GB2028
BASIC SERVICE INFORMATION
EAS2GB2029ELECTRICAL SYSTEM
Electrical parts handling
ECA
NOTICE
Never disconnect a battery lead while the
engine is running; otherwise, the electrical
components could be damaged.
ECA
NOTICE
When disconnecting the battery leads from
the battery, be sure to disconnect the nega-
tive battery lead first, then the positive bat-
tery lead. If the positive battery lead is
disconnected first and a tool or similar item
contacts the vehicle, a spark could be gen-
erated, which is extremely dangerous.
TIP
If a battery lead is difficult to disconnect due to
rust on the battery terminal, remove the rust us-
ing hot water.
ECA
NOTICE
Be sure to connect the battery leads to the
correct battery terminals. Reversing the
battery lead connections could damage the
electrical components.
ECA
NOTICE
When connecting the battery leads to the
battery, be sure to connect the positive bat-
tery lead first, then the negative battery
lead. If the negative battery lead is connect-
ed first and a tool or similar item contacts
the vehicle while the positive battery lead is
being connected, a spark could be generat-
ed, which is extremely dangerous.
ECA
NOTICE
Make sure that the multi-function display
goes off after pushing and holding the en-
gine stop switch before disconnecting or
connecting any electrical components.

BASIC SERVICE INFORMATION
1-12
ECA
NOTICE
Handle electrical components with special
care, and do not subject them to strong
shocks.
ECA
NOTICE
Electrical components are very sensitive to
and can be damaged by static electricity.
Therefore, never touch the terminals and be
sure to keep the contacts clean.
TIP
Push and hold the engine stop switch to turn off
the multi-function display when resetting the
ECU (Electronic Control Unit). Disconnect the
starter motor lead of the starter relay, and then
push the starter switch. Be sure to wait for five
seconds or longer before pushing the start
switch after the multi-function display goes off.Checking the electrical system
TIP
Before checking the electrical system, make
sure that the battery voltage is at least 12 V.
ECA
NOTICE
Never insert the tester probes into the cou-
pler terminal slots. Always insert the probes
from the opposite end “a” of the coupler,
taking care not to loosen or damage the
leads.
ECA
NOTICE
For waterproof couplers, never insert the
tester probes directly into the coupler.
When performing any checks using a water-
proof coupler, use the specified test har-
ness or a suitable commercially available
test harness.
a

SPECIAL TOOLS
1-20
Digital tachometer
90890-06760
Digital tachometer
YU-39951-BThis tool is used to measure
the engine speed.
Yamaha bond No. 1215
90890-85505
(Three bond No.1215®)This sealant (Bond) is used
for crankcase mating sur-
face, etc. Tool name/Part number How to use Illustration

CONTROL FUNCTIONS
1-21
EAS2GB2031
CONTROL FUNCTIONS
EAS2GB2032INDICATOR LIGHTS AND WARNING
LIGHTS
1. Engine trouble warning light “ ”
2. Fuel level warning light “ ”
Fuel level warning light “ ”
This warning light comes on when the fuel level
drops below approximately 1.6 L (0.42 US gal,
0.35 Imp.gal). When this occurs, refuel as soon
as possible.
The electrical circuit of the warning light can be
checked by pushing the start switch. The warn-
ing light should come on for a few seconds, and
then go off.
If the warning light does not come on initially
when the start switch is pushed, or if the warn-
ing light remains on, have a Yamaha dealer
check the electrical circuit.
Engine trouble warning light “ ”
This warning light comes on or flashes if a prob-
lem is detected in the electrical circuit monitor-
ing the engine. If this occurs, have a Yamaha
dealer check the vehicle.
The electrical circuit of the warning light can be
checked by pushing the start switch. The warn-
ing light should come on for a few seconds, and
then go off.
If the warning light does not come on initially
when the start switch is pushed, or if the warn-
ing light remains on, have a Yamaha dealer
check the electrical circuit.
EAS2GB2033ENGINE STOP SWITCH
The engine stop switch “1” is located on the left
handlebar. Continue pushing the engine stop
switch till the engine comes to a stop.
After the engine stops, the multi-function dis-
play will go off and the power supply to the ECU
(Electronic Control Unit) will be cut off if the en-
gine stop switch is pushed and held.
TIP
The multi-function display will go off after one
minute if the engine stop switch is not pushed.
EAS2GB2034START SWITCH
The start switch “1” is located on the right han-
dlebar. Push this switch to crank the engine
with the starter.
EAS2GB2035CLUTCH LEVER
The clutch lever “1” is located on the left han-
dlebar. The clutch lever disengages or engag-
es the clutch.
Pull the clutch lever toward the handlebar to
disengage the clutch, and release the lever to
engage the clutch.
12

CONTROL FUNCTIONS
1-22
EAS2GB2036SHIFT PEDAL
The shift pedal “1” has adopted a method of 1
down & 5 ups (press-down & kick-ups).
Press it down for N (neutral) to 1st, and kick it
up for 2nd to 6th.
Recommended shift points
The recommended shift points during accelera-
tion and deceleration are shown in the table be-
low.
EAS2GB2037KICKSTARTER LEVER
The kickstarter lever “1” is in the right of the
chassis.
To start the engine, pull out and push down the
kickstarter lever with your foot.
EAS2GB2038
THROTTLE GRIP
The throttle grip “1” is located on the right han-
dlebar. The throttle grip accelerates or deceler-
ates the engine. For acceleration, turn the grip
toward you; for deceleration, turn it away from
you.
EAS2GB2039FRONT BRAKE LEVER
The front brake lever “1” is located on the right
handlebar. Pull it toward the handlebar to acti-
vate the front brake.
EAS2GB2040REAR BRAKE PEDAL
The rear brake pedal “1” is in the right of the
chassis. Press down on the brake pedal to ac-
tivate the rear brake. Shift up points
1st  2nd: 20 km/h (12 mi/h)
2nd  3rd: 30 km/h (19 mi/h)
3rd  4th: 40 km/h (25 mi/h)
4th  5th: 50 km/h (31 mi/h)
5th  6th: 60 km/h (37 mi/h)
Shift down points
6th  5th: 45 km/h (28 mi/h)
5th  4th: 35 km/h (22 mi/h)
4th  3rd: 25 km/h (16 mi/h)
3rd  2nd: 25 km/h (16 mi/h)
2nd  1st: 25 km/h (16 mi/h)
1
1
1

CONTROL FUNCTIONS
1-23
EAS2GB2041SIDESTAND
This sidestand “1” is used to support only the
machine when standing or transporting it.
EWA
WARNING
• Never apply additional force to the sides-
tand.
• Hold up the sidestand before starting out.
EAS2GB2042STARTER KNOB/IDLE ADJUSTING SCREW
Starting a cold engine requires a larger amount
of intake air, which is supplied by the starter
knob/idle screw “1”.
Pulling the knob toward “a” turns ON the start-
er, resulting in a larger amount of intake air.
Pushing the knob toward “b” turns OFF the
starter.
EWA
WARNING
While handling the starter knob/idle screw,
take care not to burn yourself on exhaust
pipes.
EAS2GB2043
FUEL TANK CAP
Fuel tank cap “1” is located under the fuel tank
cap cover “2”.
Remove the fuel tank cap cover to open the fuel
tank cap.
TIP
• To remove the fuel tank cap cover, insert fin-
gers under part “a”, and then use both hands
to lift it up towards the rear of the vehicle.
• Install the fuel tank cap cover after placing the
bands “3” all the way in under the seat.
1
ab1
1
23
a
2

STARTING AND BREAK-IN
1-32
EAS2GB2050
STARTING AND BREAK-IN
EAS2GB2051FUEL
Always use the recommended fuel as stated
below. Also, be sure to use new gasoline the
day of a race.
ECA
NOTICE
Use only unleaded gasoline. The use of
leaded gasoline will cause severe damage
to the engine internal parts such as valves,
piston rings, and exhaust system, etc.
TIP
Your Yamaha engine has been designed to use
premium unleaded gasoline with a pump oc-
tane number [(R+M)/2] of 91 or higher, or a re-
search octane number of 95 or higher. If
knocking (or pinging) occurs, use a gasoline of
a different brand.
EWA
WARNING
• For refueling, be sure to stop the engine
and use enough care not to spill any fuel.
Also be sure to avoid refueling close to a
fire.
• Refuel after the engine, exhaust pipe, etc.
have cooled off.
Gasohol (For USA and Canada)
There are two types of gasohol: gasohol con-
taining ethanol and that containing methanol.
Gasohol containing ethanol can be used if the
ethanol content does not exceed 10%. Gasohol
containing methanol is not recommended by
Yamaha because it can cause damage to the
fuel system or vehicle performance problems.
EAS2GB2052HANDLING NOTEEWA
WARNING
Never start or run the engine in a closed ar-
ea. The exhaust fumes are poisonous; they
can cause loss of consciousness and death
in a very short time. Always operate the ma-
chine in a well-ventilated area.
ECA
NOTICE
• Unlike a two-stroke engine, this engine
cannot be kick started when the throttle is
open because the kickstarter may kick
back. Also, if the throttle is open the air/
fuel mixture may be too lean for the engine
to start.
• Before starting the machine, perform the
checks in the pre-operation check list.
EAS2GB2053AIR FILTER MAINTENANCE
According to “CLEANING THE AIR FILTER
ELEMENT” section in the CHAPTER 3, apply
the foam-air-filter oil or its equivalent to the ele-
ment. (Excess oil in the element may adversely
affect engine starting.)
EAS2GB2054STARTING A COLD ENGINEECA
NOTICE
For maximum engine life, never accelerate
hard when the engine is cold!
In order for the ignition circuit cut-off system to
enable starting, one of the following conditions
must be met:
• The transmission is in the neutral position.
• The transmission is in gear with the clutch le-
ver pulled.
1. Pull the starter knob/idle screw “1” to its full
length.
TIP
When the ambient temperature is 15°C (59°F)
or below, use the starter knob/idle screw.
2. Completely close the throttle.
3. Start the engine by pushing the start switch.
If the engine fails to start when using the
start switch, release it, wait a few seconds,
and then try again.
Each starting attempt should be as short as
possible to preserve the battery. Do not
crank the engine more than 10 seconds on
any one attempt. If the engine does not start
with the starter motor, try using the kickstart-
er. Recommended fuel
Premium unleaded gasoline
Fuel tank capacity
7.5 L (1.98 US gal, 1.65 lmp.gal)
Fuel reserve amount
1.6 L (0.42 US gal, 0.35 lmp.gal)
1

STARTING AND BREAK-IN
1-33
ECA
NOTICE
If the starter motor will not turn when the
start switch is pushed, stop pushing it im-
mediately in order to avoid placing extra
load on the starter motor, and start the en-
gine by using the kickstarter.
TIP
If the engine fails to start, push the engine stop
switch and give the kickstarter 10 to 20 slow
kicks at full throttle in order to clear the engine
of the rich air-fuel mixture retained in it.
4. When the engine starts running, warm this
up one or two minutes at a steady speed (of
3000 to 5000 r/min), and then return the
starter knob/idle screw to its original posi-
tion.
EWA
WARNING
Since exhaust gas contains harmful ingre-
dients, do not start or warm it up at an ill-
ventilated place or a closed narrow place.
5. To stop the engine, push the engine stop
switch “1”.
TIP
Continue pushing the engine stop switch till the
engine comes to a full stop.Starting with the kickstarter
When using the kickstarter to start the engine,
follow the procedures as described below.
1. Fold out the kickstarter lever, push it down
lightly with your foot until resistance is felt.
2. With the throttle fully closed,push the kick-
starter down lightly until the gears engage,
and then push it down smoothly but forceful-
ly.
EWA
WARNING
Do not open the throttle while kicking the
kickstarter lever. Otherwise, the kickstarter
lever may kick back.
TIP
If the engine fails to start, push the engine stop
switch and give the kickstarter 10 to 20 slow
kicks at full throttle in order to clear the engine
of the rich air-fuel mixture retained in it.
EAS2GB2055STARTING A WARM ENGINE
Follow the same procedure as for starting a
cold engine with the exception that the starter is
not required when the engine is warm.
TIP
If it fails to start, fully open the throttle grip and
give 10 to 20 slow kicks to clear the engine of
the rich air-fuel mixture retained in it.

STARTING AND BREAK-IN
1-34
EAS2GB2056BREAK-IN PROCEDURES
A break-in is important so that rotating portion,
sliding surfaces, and mounted areas may fit
one another, and that the rider may become ac-
customed to the machine.
ECA
NOTICE
Before running, do maintenance on the air
filter element.
Refer to “CLEANING THE AIR FILTER ELE-
MENT” on page 3-14.
1. After warming up the engine, drive it for
about 20 minutes at a throttle opening of 1/2
or less.
2. Make a pit stop, and check mounted areas
for looseness, oil leaks, or other problems.
3. Then, drive it for about 40 minutes at a throt-
tle opening of 3/4 or less.
4. Make a pit stop again, and thoroughly check
mounted areas for looseness, oil leaks, or
other problems. Thorough checks and ad-
justments are required in particular for
stretch of cables, free play of the brake,
stretch of the drive chain, looseness of the
spoke, and so on.
ECA
NOTICE
After a break-in or after each race, always
check the points shown in “TORQUE-
CHECK POINTS” for tightening torques and
retighten them. (Refer to “TORQUE-CHECK
POINTS” on page 1-36.)
Also when the following parts are replaced,
a break-in is required.
• Cylinder and Crankshaft: A break-in is re-
quired for about an hour.
• Piston, Piston ring, Valve, Camshaft, and
Gear: A break-in is required for about 30
minutes at a throttle opening of 1/2 or less.
Observe the condition of the engine careful-
ly during a break-in.
For checkpoints for a break-in, see “MAIN-
TENANCE AFTER BREAK-IN”. If any prob-
lem is found, immediately stop the engine
and make a checkup.