engine YAMAHA YBR125 2006 User Guide

INSTRUMENT AND CONTROL FUNCTIONS
3-8
3“ON” or “”
With the lever in this position, fuel flows
to the carburetor. Normal riding is done
with the lever in this position.
“RES” or “”This indicates reserve. If you run out of
fuel while riding, move the lever to this
position. Fill the tank at the first oppor-
tunity. Be sure to set the lever back to
“ON” or “” after refueling!
EAU13590
Starter (choke) lever “” Starting a cold engine requires a richer
air-fuel mixture, which is supplied by
the starter (choke).
Move the lever in direction (a) to turn on
the starter (choke).
Move the lever in direction (b) to turn off
the starter (choke).
1. Arrow mark pointing to “ON” or “”
1. Arrow mark pointing to “RES” or “”
1. Starter (choke) lever “”
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INSTRUMENT AND CONTROL FUNCTIONS
3-9
3
EAU13660
Kickstarter If the engine fails to start by pushing the
start switch, try to start it by using the
kickstarter. To start the engine, fold out
the kickstarter lever, move it down light-
ly with your foot until the gears engage,
and then push it down smoothly but
forcefully. This model is equipped with
a primary kickstarter, allowing the en-
gine to be started in any gear if the
clutch is disengaged. However, shifting
the transmission into the neutral posi-
tion before starting is recommended.
EAU14880
Adjusting the shock absorber
assemblies Each shock absorber assembly is
equipped with a spring preload adjust-
ing ring.CAUTION:
ECA10100
Never attempt to turn an adjusting
mechanism beyond the maximum orminimum settings.
WARNING
EWA10210
Always adjust both shock absorber
assemblies equally, otherwise poor
handling and loss of stability mayresult.
Adjust the spring preload as follows.
To increase the spring preload and
thereby harden the suspension, turn
the adjusting ring on each shock ab-
sorber assembly in direction (a). To de-
crease the spring preload and thereby
soften the suspension, turn the adjust-
ing ring on each shock absorber as-
sembly in direction (b).NOTE:Align the appropriate notch in the ad-
justing ring with the position indicatoron the shock absorber.
1. Kickstarter
1. Spring preload adjusting ring
2. Position indicator
Spring preload setting:
Minimum (soft):
1
Standard:
2
Maximum (hard):
5
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INSTRUMENT AND CONTROL FUNCTIONS
3-11
3
With the engine turned off:
1. Turn the key to “ON”.
2. Shift the transmission into the neutral position.
3. Push the start switch.
Does the engine start?
The neutral switch may be defective.
The motorcycle should not be ridden until
checked by a Yamaha dealer.
4. Turn the engine off.
5. Shift the transmission into gear.
6. Keep the clutch lever pulled.
7. Push the start switch.
Does the engine start?
The clutch switch may be defective.
The motorcycle should not be ridden until
checked by a Yamaha dealer.
NO
NOTE:
a warmed-up engine.
YES
The system is OK. The motorcycle can be ridden.
YES
NO
This check is most reliable if performed with
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PRE-OPERATION CHECKS
4-2
4
EAU15603
Pre-operation check list
ITEM CHECKS PAGE
FuelCheck fuel level in fuel tank.
Refuel if necessary.
Check fuel line for leakage.3-6
Engine oilCheck oil level in engine.
If necessary, add recommended oil to specified level.
Check vehicle for oil leakage.6-9
Front brakeCheck operation.
If soft or spongy, have Yamaha dealer bleed hydraulic system.
Check brake pads for wear.
Replace if necessary.
Check fluid level in reservoir.
If necessary, add recommended brake fluid to specified level.
Check hydraulic system for leakage.6-20, 6-20
Rear brakeCheck operation.
Check pedal free play.
Adjust if necessary.6-20
ClutchCheck operation.
Lubricate cable if necessary.
Check lever free play.
Adjust if necessary.6-17
Throttle gripMake sure that operation is smooth.
Check cable free play.
If necessary, have Yamaha dealer adjust cable free play and lubricate cable and
grip housing.6-13, 6-24
Control cablesMake sure that operation is smooth.
Lubricate if necessary.6-24
Drive chainCheck chain slack.
Adjust if necessary.
Check chain condition.
Lubricate if necessary.6-22, 6-23
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OPERATION AND IMPORTANT RIDING POINTS
5-1
5
EAU15950
WARNING
EWA10270


Become thoroughly familiar
with all operating controls and
their functions before riding.
Consult a Yamaha dealer re-
garding any control or function
that you do not thoroughly un-
derstand.


Never start the engine or oper-
ate it in a closed area for any
length of time. Exhaust fumes
are poisonous, and inhaling
them can cause loss of con-
sciousness and death within a
short time. Always make sure
that there is adequate ventila-
tion.


Before starting out, make sure
that the sidestand is up. If the
sidestand is not raised com-
pletely, it could contact the
ground and distract the opera-
tor, resulting in a possible lossof control.
EAU36991
Starting a cold engine In order for the starting 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 lever pulled.WARNING
EWA14160
Before starting the engine, check
the operation of the starting circuit
cut-off system according to the pro-cedure described on page 3-10.
1. Turn the fuel cock lever to “ON” or
“”.
2. Turn the key to “ON”.
3. Shift the transmission into the neu-
tral position.NOTE:When the transmission is in the neutral
position, the neutral indicator light
should be on, otherwise have a
Yamaha dealer check the electrical cir-cuit.4. Turn the starter (choke) on and
completely close the throttle. (See
page 3-8.)
5. Start the engine by pushing the
start switch or by pushing the kick-
starter lever down.
NOTE: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 usingthe kickstarter.CAUTION:
ECA11040
For maximum engine life, never ac-
celerate hard when the engine iscold!
6. When the engine is warm, turn the
starter (choke) off.
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OPERATION AND IMPORTANT RIDING POINTS
5-2
5
NOTE:The engine is warm when it responds
normally to the throttle with the starter(choke) turned off.
EAU16640
Starting a warm engine Follow the same procedure as for start-
ing a cold engine with the exception
that the starter (choke) is not required
when the engine is warm.
EAU16671
Shifting Shifting gears lets you control the
amount of engine power available for
starting off, accelerating, climbing hills,
etc.
The gear positions are shown in the il-
lustration.NOTE:To shift the transmission into the neu-
tral position, press the shift pedal down
repeatedly until it reaches the end of itstravel, and then slightly raise it.1. Shift pedal
2. Neutral position
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OPERATION AND IMPORTANT RIDING POINTS
5-3
5
CAUTION:
ECA10260


Even with the transmission in
the neutral position, do not
coast for long periods of time
with the engine off, and do not
tow the motorcycle for long dis-
tances. The transmission is
properly lubricated only when
the engine is running. Inade-
quate lubrication may damage
the transmission.


Always use the clutch while
changing gears to avoid damag-
ing the engine, transmission,
and drive train, which are not
designed to withstand theshock of forced shifting.
EAU16800
Tips for reducing fuel
consumption Fuel consumption depends largely on
your riding style. Consider the following
tips to reduce fuel consumption:

Turn the starter (choke) off as
soon as possible.


Shift up swiftly, and avoid high en-
gine speeds during acceleration.


Do not rev the engine while shifting
down, and avoid high engine
speeds with no load on the engine.


Turn the engine off instead of let-
ting it idle for an extended length of
time (e.g., in traffic jams, at traffic
lights or at railroad crossings).
EAU16841
Engine break-in There is never a more important period
in the life of your engine than the period
between 0 and 1600 km (1000 mi). For
this reason, you should read the follow-
ing material carefully.
Since the engine is brand new, do not
put an excessive load on it for the first
1600 km (1000 mi). The various parts in
the engine wear and polish themselves
to the correct operating clearances.
During this period, prolonged full-throt-
tle operation or any condition that might
result in engine overheating must be
avoided.
EAU37250
0–500 km (0–300 mi)
Avoid prolonged operation above 6000
r/min.
After every hour of operation, stop the
engine, and then let it cool for five to ten
minutes.
Vary the engine speed from time to
time. Do not operate the engine at one
set throttle position.
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OPERATION AND IMPORTANT RIDING POINTS
5-4
5500–1000 km (300–600 mi)
Avoid prolonged operation above 7500
r/min.
Rev the engine freely through the
gears, but do not use full throttle at any
time.
CAUTION:
ECA10280
After 1000 km (600 mi) of operation,the engine oil must be changed.
1000 km (600 mi) and beyond
The vehicle can now be operated nor-
mally.CAUTION:
ECA10310


Keep the engine speed out of
the tachometer red zone.


If any engine trouble should oc-
cur during the engine break-in
period, immediately have a
Yamaha dealer check the vehi-cle.
EAU37200
Parking When parking, stop the engine, remove
the key from the main switch, and then
turn the fuel cock lever to “OFF” or “”.
WARNING
EWA10310


Since the engine and exhaust
system can become very hot,
park in a place where pedestri-
ans or children are not likely to
touch them.


Do not park on a slope or on soft
ground, otherwise the vehiclemay overturn.
CAUTION:
ECA10380
Never park in an area where there
are fire hazards such as grass orother flammable materials.
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PERIODIC MAINTENANCE AND MINOR REPAIR
6-4
6
EAU18660
NOTE:

The air filter needs more frequent service if you are riding in unusually wet or dusty areas.


Hydraulic brake service
Regularly check and, if necessary, correct the brake fluid level.
Every two years replace the internal components of the brake master cylinder and caliper, and change the brake fluid.Replace the brake hoses every four years and if cracked or damaged.
21*CarburetorCheck starter (choke) operation.
Adjust engine idling speed.√√√√√ √
22 Engine oilChange.
Check oil level and vehicle for oil leakage.√√√√√ √
23*Front and rear brake
switchesCheck operation.√√√√√ √
24Moving parts and ca-
blesLubricate.√√√√ √
25*Throttle grip housing
and cableCheck operation and free play.
Adjust the throttle cable free play if necessary.
Lubricate the throttle grip housing and cable.√√√√ √
26*Air induction systemCheck the air cut-off valve, reed valve, and hose for dam-
age.
Replace any damaged parts if necessary.√√√√ √
27*Lights, signals and
switchesCheck operation.
Adjust headlight beam.√√√√√ √ NO. ITEM CHECK OR MAINTENANCE JOBODOMETER READING (× 1000 km)
ANNUAL
CHECK
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PERIODIC MAINTENANCE AND MINOR REPAIR
6-8
6
EAU19602
Checking the spark plug The spark plug is an important engine
component, which is easy to check.
Since heat and deposits will cause any
spark plug to slowly erode, the spark
plug should be removed and checked
in accordance with the periodic mainte-
nance and lubrication chart. In addition,
the condition of the spark plug can re-
veal the condition of the engine.
To remove the spark plug
1. Remove the spark plug cap.
2. Remove the spark plug as shown,
with the spark plug wrench includ-
ed in the owner’s tool kit.To check the spark plug
1. Check that the porcelain insulator
around the center electrode of the
spark plug is a medium-to-light tan
(the ideal color when the vehicle is
ridden normally).
NOTE:
If the spark plug shows a distinctly dif-
ferent color, the engine could be defec-
tive. Do not attempt to diagnose such
problems yourself. Instead, have aYamaha dealer check the vehicle.
2. Check the spark plug for electrode
erosion and excessive carbon or
other deposits, and replace it if
necessary.To install the spark plug
1. Measure the spark plug gap with a
wire thickness gauge and, if nec-
essary, adjust the gap to specifica-
tion.
2. Clean the surface of the spark plug
gasket and its mating surface, and
then wipe off any grime from the
spark plug threads.
1. Spark plug cap
1. Spark plug wrench
Specified spark plug:
NGK/CR6HSA1. Spark plug gapSpark plug gap:
0.6–0.7 mm (0.024–0.028 in)
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