engine YAMAHA YBR125 2003 User Guide

Fuel cock

$
ON
OFF
RES
FUEL
The fuel cock supplies fuel from the tank to the carburetor
while filtering it also.
The fuel cock has three positions:
OFF: With the fuel cock in this position, fuel will not flow.
Always set the fuel cock to this position when the
engine is not running.
ON: With the fuel cock in this position, fuel flows to the carburetor. Set the fuel cock to this position when
starting the engine and while riding.
RES: This indicates reserve. If you run out of fuel while
riding, set the fuel cock to this position.
Fill the tank at the first opportunity. be sure to set
fuel cock back to “ON” after refueling!
Fuel cock

$
ON
OFF
RES
FUEL
The fuel cock supplies fuel from the tank to the carburetor
while filtering it also.
The fuel cock has three positions:
OFF: With the fuel cock in this position, fuel will not flow.
Always set the fuel cock to this position when the
engine is not running.
ON: With the fuel cock in this position, fuel flows to the carburetor. Set the fuel cock to this position when
starting the engine and while riding.
RES: This indicates reserve. If you run out of fuel while
riding, set the fuel cock to this position.
Fill the tank at the first opportunity. be sure to set
fuel cock back to “ON” after refueling!

Starting a cold engine requires a richer air-fuel mixture. A
separate starter circuit supplies the mixture.
Pull the starter knob up to open the circuit for starting. When
the engine has warmed up, push the knob down to close
the circuit.

% Starter lever
1. Starter lever
1
Starting a cold engine requires a richer air-fuel mixture. A
separate starter circuit supplies the mixture.
Pull the starter knob up to open the circuit for starting. When
the engine has warmed up, push the knob down to close
the circuit.

% Starter lever
1. Starter lever
1

 If improper operation is noted, consult a Yamaha dealer
or other qualified mechanic immediately.
↓
↓ ↓
↓
↓
↓
↓ ↓
↓
↓↓
↓ ↓
↓
↓
Clutch switch operation check
Check the operation of the clutch switch against the
information below.
↓
↓ ↓
↓
↓
TURN MAIN SWITCH TO “ON” AND
ENGINE STOP SWITCH TO “ ”.
TRANSMISSION IS IN GEAR.
PULL IN CLUTCH LEVER AND PUSH STARTER SWITCH.
ENGINE WILL START
CLUTCH SWITCH IS OK
WARNING:

 If improper operation is noted, consult a Yamaha dealer
or other qualified mechanic immediately.
↓
↓ ↓
↓
↓
↓
↓ ↓
↓
↓↓
↓ ↓
↓
↓
Clutch switch operation check
Check the operation of the clutch switch against the
information below.
↓
↓ ↓
↓
↓
TURN MAIN SWITCH TO “ON” AND
ENGINE STOP SWITCH TO “ ”.
TRANSMISSION IS IN GEAR.
PULL IN CLUTCH LEVER AND PUSH STARTER SWITCH.
ENGINE WILL START
CLUTCH SWITCH IS OK
WARNING:

PRE-OPERATION CHECKS
Before using this motorcycle, check the following points:
ITEM ROUTINE
PAGE
Front brake
Check operation, condition and free play.
Adjust if necessary
Clutch
Throttle grip / cableCheck for smooth operation.
Lubricate / Adjust if necessary
Check oil level / add oil as necessary
Engine oil
Drive chainCheck chain slack and condition. Lubricate if necessary
Adjust if necessary.
Air filter
Control and meter cableCheck tire pressure, wear, damage and spoke tightness
Check for smooth operation.
Lubricate if necessary4-3 ~ 4-4
6-16 ~ 6-20
4-8 , 6-14 , 6-24
4-4 , 6-6 , 6-9
6-21 ~ 6-23
6-10 ~ 6-11
4-5 ~ 4-8 , 6-26
6-23 Check operation, condition and free play.
Adjust if necessary
Wheels / Tires
Clean and oil it frequently.4-8 , 6-20 Rear brakeCheck operation, free play, fluid level and fluid leakage.
Top-up with DOT #4 (or DOT #3) brake fluid if necessary.

PRE-OPERATION CHECKS
Before using this motorcycle, check the following points:
ITEM ROUTINE
PAGE
Front brake
Check operation, condition and free play.
Adjust if necessary
Clutch
Throttle grip / cableCheck for smooth operation.
Lubricate / Adjust if necessary
Check oil level / add oil as necessary
Engine oil
Drive chainCheck chain slack and condition. Lubricate if necessary
Adjust if necessary.
Air filter
Control and meter cableCheck tire pressure, wear, damage and spoke tightness
Check for smooth operation.
Lubricate if necessary4-3 ~ 4-4
6-16 ~ 6-20
4-8 , 6-14 , 6-24
4-4 , 6-6 , 6-9
6-21 ~ 6-23
6-10 ~ 6-11
4-5 ~ 4-8 , 6-26
6-23 Check operation, condition and free play.
Adjust if necessary
Wheels / Tires
Clean and oil it frequently.4-8 , 6-20 Rear brakeCheck operation, free play, fluid level and fluid leakage.
Top-up with DOT #4 (or DOT #3) brake fluid if necessary.



NOTE:
Pre-operation checks should be made each time the motorcycle is used. Su\
ch an inspection can be thoroughly accomplished
in a very short time; and the added safety it assures is more than worth\
the time involved. If any maintenance service or
adjustment is needed, consult the chart above to refer to the pages in w\
hich the service or adjustment is described.
1. The engine, exhaust pipe, and muffler will be very hot after the engine \
has been run.
Be careful not to touch them or to allow any clothing item to contact th\
em during inspection or repair.
2. If any item is not working properly, have it inspected and repaired before operating the motorcycle.
ITEM ROUTINE
PAGE
Sidestand
Fittings / Fasteners Check all chassi fittings and fasteners.
Tighten / Adjust, if necessary
Check fuel level / top up as required.
Fuel tank
Lights, signals and switches
Battery Check electrolyte level.
Replenish with “distilled water” if necessary. 6-24
4-8 , 6-5
4-8 , 6-30 ~ 6-32 6-27 ~ 6-296-24
4-9 ~ 4-10
Check for proper operation
Front brake and clutch lever pivots Check for smooth operation.
Lubricate if necessary
Check for smooth operation.
Lubricate if necessary
6-24
Check for smooth operation.
Lubricate if necessary
Rear brake and shift pedal
shafts
WARNING:

NOTE:
Pre-operation checks should be made each time the motorcycle is used. Su\
ch an inspection can be thoroughly accomplished
in a very short time; and the added safety it assures is more than worth\
the time involved. If any maintenance service or
adjustment is needed, consult the chart above to refer to the pages in w\
hich the service or adjustment is described.
1. The engine, exhaust pipe, and muffler will be very hot after the engine \
has been run.
Be careful not to touch them or to allow any clothing item to contact th\
em during inspection or repair.
2. If any item is not working properly, have it inspected and repaired before operating the motorcycle.
ITEM ROUTINE
PAGE
Sidestand
Fittings / Fasteners Check all chassi fittings and fasteners.
Tighten / Adjust, if necessary
Check fuel level / top up as required.
Fuel tank
Lights, signals and switches
Battery Check electrolyte level.
Replenish with “distilled water” if necessary. 6-24
4-8 , 6-5
4-8 , 6-30 ~ 6-32 6-27 ~ 6-296-24
4-9 ~ 4-10
Check for proper operation
Front brake and clutch lever pivots Check for smooth operation.
Lubricate if necessary
Check for smooth operation.
Lubricate if necessary
6-24
Check for smooth operation.
Lubricate if necessary
Rear brake and shift pedal
shafts
WARNING:

4-4
Brake fluid leakage
Apply the brake for several seconds. Check to see if any
brake fluid leaks out from the pipe joints or the master
cylinder.
Brake fluid may deteriorate painted surfaces or plastic parts.
Never spill any fluid. If spilled, clean it up immediately.
If brake fluid leakage is found, ask a Yamaha dealer or
other qualified mechanic for immediate repairs. Such
leakage could indicate a hazardous condition.
OIL QUANTITY:
Total amount:
1.2 L ( 0.264 Imp gal, 0.317 US gal)
Periodic oil change:
1.0 L ( 0.220 Imp gal, 0.264 US gal)
Engine oil
(See page 6-6 for details)
Make sure the engine oil is at the specified level. Add oil as
necessary.
Check the oil level in a daily manner and top it up if
necessary.
CAUTION:
WARNING:
CAUTION:
4-4
Brake fluid leakage
Apply the brake for several seconds. Check to see if any
brake fluid leaks out from the pipe joints or the master
cylinder.
Brake fluid may deteriorate painted surfaces or plastic parts.
Never spill any fluid. If spilled, clean it up immediately.
If brake fluid leakage is found, ask a Yamaha dealer or
other qualified mechanic for immediate repairs. Such
leakage could indicate a hazardous condition.
OIL QUANTITY:
Total amount:
1.2 L ( 0.264 Imp gal, 0.317 US gal)
Periodic oil change:
1.0 L ( 0.220 Imp gal, 0.264 US gal)
Engine oil
(See page 6-6 for details)
Make sure the engine oil is at the specified level. Add oil as
necessary.
Check the oil level in a daily manner and top it up if
necessary.
WARNING:
CAUTION:
CAUTION:

4-8Wheels
To ensure maximum performance, long service, and safe
operation, note the following:
1. Always inspect the wheels before a ride. Check for
cracks, bends, or warpage of the wheel; be sure the
spokes are tight and undamaged. If any abnormal
condition exists in a wheel, consult a Yamaha dealer or
other qualified mechanic. Do not attempt even small
repairs to the wheel. If a wheel is deformed or cracked,
it must be replaced.
2. Tires and wheels should be balanced whenever either one is changed or replaced. Failure to have a wheel
balanced can result in poor performance, adverse
handling characteristics, and shortened tire life.
3. After installing a tire, ride conservatively to allow the tire to seat itself on the rim properly. Failure to allow
proper seating may cause tire failure, resulting in
damage to the motorcycle and injury to the rider.
Clutch
( See page 6-20 for details)
Check the free play in the clutch lever, and make sure the
lever operates properly. If the free play is incorrect, adjust
it.
Throttle grip (See page 6-24 for details)
Turn the throttle grip to see if it operates properly, and check
the free play.
Make sure the grip returns by spring force when released.
Ask a Yamaha dealer or other qualified mechanic to make
any necessary adjustments.
Fitting/Fasteners
Alway check the tightness of chassis fittings and fasteners
before a ride. Use the chart on page 6-5 to find the correct
torque.
Switches
Check the operation of the starter switch, main switch, “
Engine Stop” switch.
4-8Wheels
To ensure maximum performance, long service, and safe
operation, note the following:
1. Always inspect the wheels before a ride. Check for
cracks, bends, or warpage of the wheel; be sure the
spokes are tight and undamaged. If any abnormal
condition exists in a wheel, consult a Yamaha dealer or
other qualified mechanic. Do not attempt even small
repairs to the wheel. If a wheel is deformed or cracked,
it must be replaced.
2. Tires and wheels should be balanced whenever either one is changed or replaced. Failure to have a wheel
balanced can result in poor performance, adverse
handling characteristics, and shortened tire life.
3. After installing a tire, ride conservatively to allow the tire to seat itself on the rim properly. Failure to allow
proper seating may cause tire failure, resulting in
damage to the motorcycle and injury to the rider.
Clutch
( See page 6-20 for details)
Check the free play in the clutch lever, and make sure the
lever operates properly. If the free play is incorrect, adjust
it.
Throttle grip (See page 6-24 for details)
Turn the throttle grip to see if it operates properly, and check
the free play.
Make sure the grip returns by spring force when released.
Ask a Yamaha dealer or other qualified mechanic to make
any necessary adjustments.
Fitting/Fasteners
Alway check the tightness of chassis fittings and fasteners
before a ride. Use the chart on page 6-5 to find the correct
torque.
Switches
Check the operation of the starter switch, main switch, “
Engine Stop” switch.

$Always wipe off spilled fuel immediately with a dry and clean
soft cloth. Fuel may deteriorate painted surfaces or plastic
parts. Fuel
1. Fuel level 2. Filler tube
Make sure there is sufficient fuel in the tank.
Do not overfill the fuel tank. Avoid spilling fuel on the
hot engine. Do not fill the fuel tank above the bottom of
the filler tube as shown in the illustration or it may
overflow when the fuel heats up later and expands.
Recommended fuel:
UNLEADED FUEL
Fuel tank capacity:
Total:
13.0 L ( 2.860 Imp gal, 3.434 US gal)
Reserve:
1.7 L ( 0.374 Imp gal, 0.450 Us gal)
WARNING:
CAUTION:
Your Yamaha engine has been designed to use regular
unleaded gasoline with a pump octane number ([R+m]/2)
of 86 or higher, or research octane number of 91 or higher.
If knocking or pinging occurs, use a different brand of
gasoline or premium unleaded fuel. Unleaded fuel will give
you longer spark plug life and reduced maintenance cost.
If unleaded gasoline is not available, then leaded regular
gasoline can be used.
Gasohol
There are two types of gasohol; gasohol containing ethanol
and that containing methanol. Gasohol containing ethanol
can be used if ethanol content does not exceed 10%.
Gasohol containing methanol is not recommended by
Yamaha because it can cause fuel system damage or
vehicle performance problems.
$Always wipe off spilled fuel immediately with a dry and clean
soft cloth. Fuel may deteriorate painted surfaces or plastic
parts. Fuel
1. Fuel level 2. Filler tube
Make sure there is sufficient fuel in the tank.
Do not overfill the fuel tank. Avoid spilling fuel on the
hot engine. Do not fill the fuel tank above the bottom of
the filler tube as shown in the illustration or it may
overflow when the fuel heats up later and expands.
Recommended fuel:
UNLEADED FUEL
Fuel tank capacity:
Total:
13.0 L ( 2.860 Imp gal, 3.434 US gal)
Reserve:
1.7 L ( 0.374 Imp gal, 0.450 Us gal)
WARNING:
CAUTION:
Your Yamaha engine has been designed to use regular
unleaded gasoline with a pump octane number ([R+m]/2)
of 86 or higher, or research octane number of 91 or higher.
If knocking or pinging occurs, use a different brand of
gasoline or premium unleaded fuel. Unleaded fuel will give
you longer spark plug life and reduced maintenance cost.
If unleaded gasoline is not available, then leaded regular
gasoline can be used.
Gasohol
There are two types of gasohol; gasohol containing ethanol
and that containing methanol. Gasohol containing ethanol
can be used if ethanol content does not exceed 10%.
Gasohol containing methanol is not recommended by
Yamaha because it can cause fuel system damage or
vehicle performance problems.

1. Be very careful if you are carrying object while riding
the motorcycle
2. Be vareful not to put any object near battery terminals.
Electrical failure or acid corrosion may occur.
OPERATION AND IMPORTANT RIDING POINTS
Before riding this motorcycle, become thoroughly
familiar with all operating controls and their functions.
Consult a Yamaha dealer regarding any control or
function that you do not thoroughly understand.
Never start your engine or let it run for any
length of time in a closed area.
The exhaust fumes are poisonous and can cause loss
of consciousness and death within a short time. Always
operate your machine in an area with adequate
ventilation.
Before starting out, always be sure the sidestand is up.
Failure to retract the sidestand completely can result
in a serious accident when you try to turn a corner.
CAUTION:
CAUTION:
 1. Be very careful if you are carrying object while riding
the motorcycle
2. Be vareful not to put any object near battery terminals.
Electrical failure or acid corrosion may occur.
OPERATION AND IMPORTANT RIDING POINTS
Before riding this motorcycle, become thoroughly
familiar with all operating controls and their functions.
Consult a Yamaha dealer regarding any control or
function that you do not thoroughly understand.
Never start your engine or let it run for any
length of time in a closed area.
The exhaust fumes are poisonous and can cause loss
of consciousness and death within a short time. Always
operate your machine in an area with adequate
ventilation.
Before starting out, always be sure the sidestand is up.
Failure to retract the sidestand completely can result
in a serious accident when you try to turn a corner.
CAUTION:
CAUTION:

5-2
Starting a cold engine
1. Turn the fuel cock to “ON”.
2. Turn the main switch to “ON” and the engine stop switch
to “ “.
3. Shift transmission into neutral.
NOTE:
When the transmission is in neutral, the neutral indicator
light should be on. If the light does not come on, ask a
Yamaha dealer to inspect it.
4. Fully open the starter (CHOKE) and completely close the throttle grip.
5. Start the engine by pushing the starter switch.
NOTE:
This motorcycle is equipped with a starting and an ignition
circuit cut-off switch.
1. The engine can be started only under the following conditions:
a. The transmission is in neutral.
b. The transmission is in gear and the clutch is disengaged.
2. The motorcycle must not be ridden when the sidestand is down. NOTE:
If the engine fails to start, release the starter switch, wait a
few seconds, then try again. Each attempt should be as
short as possible to preseve the battery. Do not crank the
engine more than 10 seconds on any one attempt.
6. After starting the engine, turn back the starter to an
intermediate position.
NOTE:
To obtain maximum engine life and service, do not ever
thoroughly accelerate it while the engine is cold.
7. After warming up the engine, turn back the starter (CHOKE) completely.
NOTE:
The engine is warm when it responds normally to the throttle
with the starter turned off.
5-2
Starting a cold engine
1. Turn the fuel cock to “ON”.
2. Turn the main switch to “ON” and the engine stop switch
to “ “.
3. Shift transmission into neutral.
NOTE:
When the transmission is in neutral, the neutral indicator
light should be on. If the light does not come on, ask a
Yamaha dealer to inspect it.
4. Fully open the starter (CHOKE) and completely close the throttle grip.
5. Start the engine by pushing the starter switch.
NOTE:
This motorcycle is equipped with a starting and an ignition
circuit cut-off switch.
1. The engine can be started only under the following conditions:
a. The transmission is in neutral.
b. The transmission is in gear and the clutch is disengaged.
2. The motorcycle must not be ridden when the sidestand is down. NOTE:
If the engine fails to start, release the starter switch, wait a
few seconds, then try again. Each attempt should be as
short as possible to preseve the battery. Do not crank the
engine more than 10 seconds on any one attempt.
6. After starting the engine, turn back the starter to an
intermediate position.
NOTE:
To obtain maximum engine life and service, do not ever
thoroughly accelerate it while the engine is cold.
7. After warming up the engine, turn back the starter (CHOKE) completely.
NOTE:
The engine is warm when it responds normally to the throttle
with the starter turned off.