engine YAMAHA YBR125 2003 Service Manual

6-37Never check the fuel system while smoking or in the
vicinity of an open flame.
Check if there is
fuel in the fuel tank
Use electric
starter
Remove spark
plug and check
electrode
Use electric starter 1. Fuel
2. Compression
3. Ignition
4. BatteryEnough fuel
No fuel
There is compression
No compression
Wet
Dry
Engine turns
over quickly
Engine turns
over slowlySupply fuel
Go to ignition check
Ask Yamaha dealer to inspect
Wipe clean with dry cloth and correct
spark plug gap or replace spark plugs
Ask Yamaha dealer to inspect
Battery good
Check fluid,
recharge and check
connections
Troubleshooting chart
Go to compression
check
Engine doesn’t start, go
to compression check
Open the throttle hal-way
and start the engine
Engine doesn’t start, ask
Yamaha dealer to inspect.Engine doesn’t start,
go to battery check
WARNING:
6-37Never check the fuel system while smoking or in the
vicinity of an open flame.
Check if there is
fuel in the fuel tank
Use electric
starter
Remove spark
plug and check
electrode
Use electric starter 1. Fuel
2. Compression
3. Ignition
4. BatteryEnough fuel
No fuel
There is compression
No compression
Wet
Dry
Engine turns
over quickly
Engine turns
over slowlySupply fuel
Go to ignition check
Ask Yamaha dealer to inspect
Wipe clean with dry cloth and correct
spark plug gap or replace spark plugs
Ask Yamaha dealer to inspect
Battery good
Check fluid,
recharge and check
connections
Troubleshooting chart
Go to compression
check
Engine doesn’t start, go
to compression check
Open the throttle hal-way
and start the engine
Engine doesn’t start, ask
Yamaha dealer to inspect.Engine doesn’t start,
go to battery check
WARNING:

7-1
CLEANING AND STORAGE
A. CLEANING
Frequent, thorough cleaning of your motorcycle will not only
enhance its appearance but will improve its general
performance and extend the useful life of many components.
1. Before cleaning the motorcycle:
a. Block off the end of the exhaust pipe to prevent water entry; a plastic bag and strong rubber band may be
used.
b. Make sure the spark plug and all filler caps are properly
installed.
2. If the engine case is excessively greasy, apply degreaser with a paint brush. Do not apply degreaser
to the chain, sprockets, or wheel axles.
3. Rinse the dirt and degreaser off with a garden hose, Use only enough pressure to do the job.
Excessive hose pressure may cause water seepage and
deterioration of wheel bearings, front fork, brakes,
transmission seals and electrical parts. Many expensive repair bills have resulted from improper
high pressure detergent applications such as those
available in coin-operated car washers.
4. Once the majority of the dirt has been hosed off, wash
all surfaces with warm water and mild, detergent-type
soap. An old toothbrush or bottle brush is handy for
hard-to-get-at places.
5. Rinse the motorcycle off immediately with clean water
and dry all surfaces with a chamois, clean towel, or
soft absorbent cloth.
6. Dry the chain and lubricate it to prevent rust.
7. Clean the seat with a vinyl upholstery cleaner to keep the cover pliable and glossy.
8. Automotive-type wax may be applied to all painted and
chrome-plated surfaces. Avoid combination cleaner-
waxes. Many contain abrasives which may mar the paint
or protective finish. When finished, start the engine and
let it idle for several minutes.
CAUTION:
CAUTION:
7-1
CLEANING AND STORAGE
A. CLEANING
Frequent, thorough cleaning of your motorcycle will not only
enhance its appearance but will improve its general
performance and extend the useful life of many components.
1. Before cleaning the motorcycle:
a. Block off the end of the exhaust pipe to prevent water entry; a plastic bag and strong rubber band may be
used.
b. Make sure the spark plug and all filler caps are properly
installed.
2. If the engine case is excessively greasy, apply degreaser with a paint brush. Do not apply degreaser
to the chain, sprockets, or wheel axles.
3. Rinse the dirt and degreaser off with a garden hose, Use only enough pressure to do the job.
Excessive hose pressure may cause water seepage and
deterioration of wheel bearings, front fork, brakes,
transmission seals and electrical parts. Many expensive repair bills have resulted from improper
high pressure detergent applications such as those
available in coin-operated car washers.
4. Once the majority of the dirt has been hosed off, wash
all surfaces with warm water and mild, detergent-type
soap. An old toothbrush or bottle brush is handy for
hard-to-get-at places.
5. Rinse the motorcycle off immediately with clean water
and dry all surfaces with a chamois, clean towel, or
soft absorbent cloth.
6. Dry the chain and lubricate it to prevent rust.
7. Clean the seat with a vinyl upholstery cleaner to keep the cover pliable and glossy.
8. Automotive-type wax may be applied to all painted and
chrome-plated surfaces. Avoid combination cleaner-
waxes. Many contain abrasives which may mar the paint
or protective finish. When finished, start the engine and
let it idle for several minutes.
CAUTION:
CAUTION:

7-2 B. STORAGE
Long term storage (30 days or more) of your machine will
require some preventive procedures to guard against
deterioration. After thoroughly cleaning the machine,
prepare for storage as follows:
1. Drain the fuel tank, fuel lines, and carburetor float
bowl(s).
2. Remove the spark plug(s), pour about one tablespoon
of SAE 20W50 motor oil in the spark plug hole(s) and
reinstall the spark plug(s).
Crank the engine over several times (with the
ignition off) to coat the cylinder walls with oil.
3. Remove the drive chain. Clean it thoroughly with
solvent and lubricate it.
Reinstall the chain or store it in a plastic bag
(tied to frame for safe-keeping).
4. Lubricate all control cables.
5. Block up the frame to raise both wheels off the
ground.
6. Tie a plastic bag over the exhaust pipe outlet to
prevent moisture from entering.7. If storing in a humid or salt-air atmosphere, coat
all exposed metal surfaces with a light film of
oil. Do not apply oil to any rubber parts or the
seat cover.
8. Remove the battery and charge it. Store it in a dry place
and recharge it once a month. Do not store the battery
in an excessively warm or cold place (less than 0ºC
(30ºF) or more than 30ºC (90ºF).
NOTE:
Make any necessary repairs before storing the machine.
7-2 B. STORAGE
Long term storage (30 days or more) of your machine will
require some preventive procedures to guard against
deterioration. After thoroughly cleaning the machine,
prepare for storage as follows:
1. Drain the fuel tank, fuel lines, and carburetor float
bowl(s).
2. Remove the spark plug(s), pour about one tablespoon
of SAE 20W50 motor oil in the spark plug hole(s) and
reinstall the spark plug(s).
Crank the engine over several times (with the
ignition off) to coat the cylinder walls with oil.
3. Remove the drive chain. Clean it thoroughly with
solvent and lubricate it.
Reinstall the chain or store it in a plastic bag
(tied to frame for safe-keeping).
4. Lubricate all control cables.
5. Block up the frame to raise both wheels off the
ground.
6. Tie a plastic bag over the exhaust pipe outlet to
prevent moisture from entering.7. If storing in a humid or salt-air atmosphere, coat
all exposed metal surfaces with a light film of
oil. Do not apply oil to any rubber parts or the
seat cover.
8. Remove the battery and charge it. Store it in a dry place
and recharge it once a month. Do not store the battery
in an excessively warm or cold place (less than 0ºC
(30ºF) or more than 30ºC (90ºF).
NOTE:
Make any necessary repairs before storing the machine.

8-1
SPECIFICATIONS
MODEL YBR 125 ED
Dimension: Overall length 1,980 mm ( 78 in)
Overall width 745 mm ( 29 in)
Overall height 1,050 mm ( 41 in)
Seat height 780 mm ( 31 in)
Wheel base 1,290 mm ( 51 in)
Minimum ground clearance 175 mm ( 7 in)
Basic weight: 108 Kg ( 238 lb)
With oil and without fuel: 119 Kg ( 262 lb)
Minimum turning radius: 1,750 mm ( 70 in)
Engine: Type Air cooled, 4-stroke gasoline, SOHC
Cylinder arrangement Single cylinder, Forward inclined
Displacement 123.7 cm
3
Bore x Stroke 54 x 54 mm ( 2.13 x 2.13 in)
Compression rate 10.0 : 1
Starting system Electric starter
Lubrication system Wet sump
8-1
SPECIFICATIONS
MODEL YBR 125 ED
Dimension: Overall length 1,980 mm ( 78 in)
Overall width 745 mm ( 29 in)
Overall height 1,050 mm ( 41 in)
Seat height 780 mm ( 31 in)
Wheel base 1,290 mm ( 51 in)
Minimum ground clearance 175 mm ( 7 in)
Basic weight: 108 Kg ( 238 lb)
With oil and without fuel: 119 Kg ( 262 lb)
Minimum turning radius: 1,750 mm ( 70 in)
Engine: Type Air cooled, 4-stroke gasoline, SOHC
Cylinder arrangement Single cylinder, Forward inclined
Displacement 123.7 cm
3
Bore x Stroke 54 x 54 mm ( 2.13 x 2.13 in)
Compression rate 10.0 : 1
Starting system Electric starter
Lubrication system Wet sump

MODEL YBR 125ED
Engine oil: Type Yamalube 4 or SAE 20W50 type SH
Capacity: Periodic oil change 1.0 L ( 0.220 Imp galt, 0.264 US gal)
Total amount 1.2 L ( 0.264 Imp gal, 0.317 US gal)
Air filter: Wet type element
Fuel: Type Regular unleaded gasoline
Tank capacity 13 L ( 2.860 Imp gal, 3.434 US gal)
Reserve amount 1.7 L ( 0.374 Imp gal, 0.450 US gal)
Carburetor: Type/manufacturer VM 20 / MIKUNI
Spark plug: Type/manufacturer CR7HSA / NGK or U22FSR-U / DENSO
Gap 0.7 mm (0.028 in)
Clutch type: Wet, multi-disc
8-2
MODEL YBR 125ED
Engine oil: Type Yamalube 4 or SAE 20W50 type SH
Capacity: Periodic oil change 1.0 L ( 0.220 Imp galt, 0.264 US gal)
Total amount 1.2 L ( 0.264 Imp gal, 0.317 US gal)
Air filter: Wet type element
Fuel: Type Regular unleaded gasoline
Tank capacity 13 L ( 2.860 Imp gal, 3.434 US gal)
Reserve amount 1.7 L ( 0.374 Imp gal, 0.450 US gal)
Carburetor: Type/manufacturer VM 20 / MIKUNI
Spark plug: Type/manufacturer CR7HSA / NGK or U22FSR-U / DENSO
Gap 0.7 mm (0.028 in)
Clutch type: Wet, multi-disc
8-2