2003 YAMAHA YBR125 Owners Manual

Valve clearance adjustment
The correct valve clearance changes with use, resulting in
improper fuel/air supply or engine noise. To prevent this,
valve clearance must be adjusted regularly. This adjustment,
however, should be left to a professional Yamaha service
technician.
Carburetor adjustment
The carburetor is a vital part of the engine. Adjusting should
be left to a Yamaha dealer who has the professional
knowledge, specialized data, and equipment to do so
properly. However, the following may be serviced by the
owner as part of routine maintenance.
The carburetor was set at Yamaha factory after many
tests. If the settings are changed, poor engine
performance and damage may result.
!
CAUTION:
Valve clearance adjustment
The correct valve clearance changes with use, resulting in
improper fuel/air supply or engine noise. To prevent this,
valve clearance must be adjusted regularly. This adjustment,
however, should be left to a professional Yamaha service
technician.
Carburetor adjustment
The carburetor is a vital part of the engine. Adjusting should
be left to a Yamaha dealer who has the professional
knowledge, specialized data, and equipment to do so
properly. However, the following may be serviced by the
owner as part of routine maintenance.
The carburetor was set at Yamaha factory after many
tests. If the settings are changed, poor engine
performance and damage may result.
!
CAUTION:

NOTE:
A diagnostic tachometer must be used for this procedure.
1. Attach the tachometer. Start the engine and warm it up
for a few minutes (normally, 1 or 2 minutes) at
approximately 1,000 to 2,000 r/min. Occasionally rev
the engine to 4,000 to 5,000 r/min. The engine is warm
when it quickly responds to the throttle.
2. Set the idle to the specified engine speed by adjusting
the throttle stop screw; turn the screw in to increase
engine speed and out to decrease engine speed.
NOTE:
If the specified idle speed cannot be obtained by performing
the above adjustment, consult a Yamaha dealer.
!

Standard idle speed:
1,300 ~ 1,400 r/min
1. Throttle stop screw
Idle speed adjustment
1
NOTE:
A diagnostic tachometer must be used for this procedure.
1. Attach the tachometer. Start the engine and warm it up
for a few minutes (normally, 1 or 2 minutes) at
approximately 1,000 to 2,000 r/min. Occasionally rev
the engine to 4,000 to 5,000 r/min. The engine is warm
when it quickly responds to the throttle.
2. Set the idle to the specified engine speed by adjusting
the throttle stop screw; turn the screw in to increase
engine speed and out to decrease engine speed.
NOTE:
If the specified idle speed cannot be obtained by performing
the above adjustment, consult a Yamaha dealer.
!

Standard idle speed:
1,300 ~ 1,400 r/min
1. Throttle stop screw
Idle speed adjustment
1

NOTE:
Before checking the throttle cable free play, the engine
idling speed should be adjusted.
The throttle cable should have an specified free play in the
turning direction at the grip flange. If the free play is incorrect,
follow the instructions below.
1. Loosen the locknut.
2. Turning the adjuster to:
Direction A : increase free play
Direction B: reduces free play
3. Tighten the locknut.
!
Free play: 3 ~ 7 mm (0.12 ~ 0.28 in)
Throttle cable adjustment
1. Free play
2. Locknut
3. Adjuster
NOTE:
Before checking the throttle cable free play, the engine
idling speed should be adjusted.
The throttle cable should have an specified free play in the
turning direction at the grip flange. If the free play is incorrect,
follow the instructions below.
1. Loosen the locknut.
2. Turning the adjuster to:
Direction A : increase free play
Direction B: reduces free play
3. Tighten the locknut.
!
Free play: 3 ~ 7 mm (0.12 ~ 0.28 in)
Throttle cable adjustment
1. Free play
2. Locknut
3. Adjuster

!
1. Spark plug gap
Spark plug inspection
The spark plug is an important engine component and is
easy to inspect. The condition of the spark plug can indicate
the condition of the engine.
The ideal color on the white porcelain insulator around the
center electrode is a medium to light tan color for a
motorcycle that is being ridden normally. Do not attempt to
diagnose any problems yourself. Instead, take the
motorcycle to a Yamaha dealer. You should periodically
remove and inspect the spark plug because heat and
deposits will cause the spark plug to slowly break down
and erode.
If electrode erosion becomes excessive, or if carbon and
other deposits are excessive, you should replace the spark
plug with the specified plug.Standard spark plug:
CR7HSA (NGK) and U22FSR-U (DENSO)
Before installing the spark plug, measure the electrode gap
with a wire thickness gauge and adjust the gap to
specification as necessary.
Spark plug gap:
0.7 mm ( 0.028 in)
When installing the plug, always clean the gasket surface
and use a new gasket. Wipe off any grime from the threads,
and torque the spark plug properly.
Spark plug torque:
12.5 N.m (1.25 Kgf.m, 9 lbf.ft)
NOTE:
If a torque wrench is not available when you are installing a
spark plug, a good estimate of the correct torque is 1/4 to
1/2 turn past finger tight. Have the spark plug torqued to
the correct value as soon as possible with a torque wrench.
!
1. Spark plug gap
Spark plug inspection
The spark plug is an important engine component and is
easy to inspect. The condition of the spark plug can indicate
the condition of the engine.
The ideal color on the white porcelain insulator around the
center electrode is a medium to light tan color for a
motorcycle that is being ridden normally. Do not attempt to
diagnose any problems yourself. Instead, take the
motorcycle to a Yamaha dealer. You should periodically
remove and inspect the spark plug because heat and
deposits will cause the spark plug to slowly break down
and erode.
If electrode erosion becomes excessive, or if carbon and
other deposits are excessive, you should replace the spark
plug with the specified plug.Standard spark plug:
CR7HSA (NGK) and U22FSR-U (DENSO)
Before installing the spark plug, measure the electrode gap
with a wire thickness gauge and adjust the gap to
specification as necessary.
Spark plug gap:
0.7 mm ( 0.028 in)
When installing the plug, always clean the gasket surface
and use a new gasket. Wipe off any grime from the threads,
and torque the spark plug properly.
Spark plug torque:
12.5 N.m (1.25 Kgf.m, 9 lbf.ft)
NOTE:
If a torque wrench is not available when you are installing a
spark plug, a good estimate of the correct torque is 1/4 to
1/2 turn past finger tight. Have the spark plug torqued to
the correct value as soon as possible with a torque wrench.

!!
Rear brake adjustment
A
a. Free play: 20 ~ 30 mm (0.8 ~ 1.2 in)
Check the free play the rear brake pedal free play should
be adjusted to 20 ~ 30 mm (0.8 ~ 1.2 in) at the brake pedal
end.
Turn the adjusting nut in direction  to increase free play
and in direction  to decrease free play.
Press the brake pedal several times and check if the wheel
turns free when the pedal is released.
For brake pedal adjustment, be sure to proceed as
follows (it is advisable to have a Yamaha dealer make
this adjustment.)
Check the operation of the brake light after adjusting
the rear brake.
1. Adjusting nut
CAUTION:
!!
Rear brake adjustment
A
a. Free play: 20 ~ 30 mm (0.8 ~ 1.2 in)
Check the free play the rear brake pedal free play should
be adjusted to 20 ~ 30 mm (0.8 ~ 1.2 in) at the brake pedal
end.
Turn the adjusting nut in direction  to increase free play
and in direction  to decrease free play.
Press the brake pedal several times and check if the wheel
turns free when the pedal is released.
For brake pedal adjustment, be sure to proceed as
follows (it is advisable to have a Yamaha dealer make
this adjustment.)
Check the operation of the brake light after adjusting
the rear brake.
1. Adjusting nut
CAUTION:

6-17
Brake light switch adjustment
The rear brake light switch is activated by the brake pedal
and is properly adjusted when the brake light comes on just
before braking takes effect. To adjust the rear brake light
switch, hold the switchbody so it does not rotate while turning
the adjusting nut.
Turn the adjusting nut in direction a to make the brake
light come on earlier.
Turn the adjusting nut in direction b to make the brake
light come on later.
1. Brake light switch 2. Adjusting nut
Checking the front brake pads and rear brake shoes
A wear indicator is provided on each brake. This indicator
allows checking of brake pad/shoe wear without
disassembling the brake.
6-17
Brake light switch adjustment
The rear brake light switch is activated by the brake pedal
and is properly adjusted when the brake light comes on just
before braking takes effect. To adjust the rear brake light
switch, hold the switchbody so it does not rotate while turning
the adjusting nut.
Turn the adjusting nut in direction a to make the brake
light come on earlier.
Turn the adjusting nut in direction b to make the brake
light come on later.
1. Brake light switch 2. Adjusting nut
Checking the front brake pads and rear brake shoes
A wear indicator is provided on each brake. This indicator
allows checking of brake pad/shoe wear without
disassembling the brake.

FRONT BRAKE
Apply the brake and inspect the wear indicator. If the wear
indicator is almost in contact with the disc plate, ask a
Yamaha dealer to replace the pads.!#REAR BRAKE
Apply the brake and inspect the wear indicator. If the
indicator reaches the wear limit line, ask a Yamaha dealer
to replace the shoes.
1. Wear indicator 2. Wear limit
1. Wear limit line 2. Wear indicator
FRONT BRAKE
Apply the brake and inspect the wear indicator. If the wear
indicator is almost in contact with the disc plate, ask a
Yamaha dealer to replace the pads.
!#REAR BRAKE
Apply the brake and inspect the wear indicator. If the
indicator reaches the wear limit line, ask a Yamaha dealer
to replace the shoes.
1. Wear indicator 2. Wear limit
1. Wear limit line 2. Wear indicator

!$
Inspecting the brake fluid level
Insufficient brake fluid may let air enter the brake system,
possibly causing the brakes to become ineffective. Before
riding, check that the brake fluid is above the lower level
and replenish when necessary. Observe these precautions:
1. When checking the fluid level, make sure the top of the
master cylinder is level by turning the handlebars.
2. Use only the designated quality brake fluid. Otherwise,
the rubber seals may deteriorate, causing leakage and
poor brake performance.
Recommended brake fluid:
DOT #4
NOTE:
If DOT #4 is not available, #3 can be used.
1. Lower level
3. Refill with the same type of brake fluid. Mixing fluids
may result in a harmful reaction and lead to poor brake
performance.
4. Be careful that water does not enter the master cylinder
when refilling. Water will significantly lower the boiling
point of the fluid and may result in vapor lock.
5. Brake fluid may deteriorate painted surfaces or plastic
parts. Always clean up spilled fluid immediately.
6. Have a Yamaha dealer check the cause if the brake
fluid level goes down.
!$
Inspecting the brake fluid level
Insufficient brake fluid may let air enter the brake system,
possibly causing the brakes to become ineffective. Before
riding, check that the brake fluid is above the lower level
and replenish when necessary. Observe these precautions:
1. When checking the fluid level, make sure the top of the
master cylinder is level by turning the handlebars.
2. Use only the designated quality brake fluid. Otherwise,
the rubber seals may deteriorate, causing leakage and
poor brake performance.
Recommended brake fluid:
DOT #4
NOTE:
If DOT #4 is not available, #3 can be used.
1. Lower level
3. Refill with the same type of brake fluid. Mixing fluids
may result in a harmful reaction and lead to poor brake
performance.
4. Be careful that water does not enter the master cylinder
when refilling. Water will significantly lower the boiling
point of the fluid and may result in vapor lock.
5. Brake fluid may deteriorate painted surfaces or plastic
parts. Always clean up spilled fluid immediately.
6. Have a Yamaha dealer check the cause if the brake
fluid level goes down.