2003 YAMAHA TTR90 light

3 - 10
INSP
ADJ
SPARK ARRESTER CLEANING (For USA)
6. Install:
Tappet cover (intake side) 1
O-ring 2
NOTE:
Apply the lithium soap base grease on the O-ring.
7. Install:
Tappet cover (exhaust side)
O-ring
Spark plug
Timing plug
Crankshaft end cover
NOTE:
Apply the lithium soap base grease on the O-ring.
8. Install:
Air filter case
Air scoop (right)
SPARK ARRESTER CLEANING (For USA)
WARNING
Be sure the exhaust pipe and muffler are
cool before cleaning the spark arrester.
Do not start the engine when cleaning the
exhaust system.
1. Remove:
Bolt (tailpipe) 1
2. Remove:
Tailpipe 2
Pull the tailpipe out of the muffler.
3. Clean:
Spark arrester
Use a wire brush to remove any carbon
deposits from the spark arrester portion
of the muffler body 3 inner surface.
Tap the tailpipe lightly and remove the
carbon deposits from the outside por-
tion a of the tailpipe.
4. Install:
Tailpipe
Insert the tailpipe into the muffler and
align the bolt hole.
Bolt (tailpipe)
T R..18 Nm (1.8 m · kg, 13 ft · lb)
New
T R..18 Nm (1.8 m · kg, 13 ft · lb)
New
T R..13 Nm (1.3 m · kg, 9.4 ft · lb)
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)
2
1
3
a
T R..7 Nm (0.7 m · kg, 5.1 ft · lb)

3 - 18
INSP
ADJ
LUBRICATION
LUBRICATION
To ensure smooth operation of all compo-
nents, lubricate your machine during setup,
after break-in, and after every race.
1All control cable
2Brake lever pivot
3Shift pedal pivot
4Footrest pivot
5Throttle-to-handlebar contact
6Drive chain
7Tube guide cable winding portion
8Throttle cable end
9Brake cable endÅUse Yamaha cable lube or equivalent on these
areas.
ıUse SAE 10W-30 motor oil or suitable chain
lubricants.
ÇLubricate the following areas with high quality,
lightweight lithium-soap base grease.
AAA
AAB
CC
78

3 - 19
INSP
ADJ
ELECTRICAL/SPARK PLUG INSPECTION
EC370000
ELECTRICAL
EC371001
SPARK PLUG INSPECTION
1. Remove:
Spark plug
2. Inspect:
Electrode 1
Wear/damage → Replace.
Insulator color 2
Normal condition is a medium to light
tan color.
Distinctly different color → Check the
engine condition.
NOTE:
When the engine runs for many hours at low
speeds, the spark plug insulator will become
sooty, even if the engine and carburetor are in
good operating condition.
3. Measure:
Plug gap a
Use a wire gauge or thickness gauge.
Out of specification → Regap.
4. Clean the plug with a spark plug cleaner
if necessary.
Spark plug gap:
0.6 ~ 0.7 mm (0.02 ~ 0.03 in)
Standard spark plug:
CR6HSA (NGK)
U20FSR-U (DENSO)
5. Tighten:
Spark plug
NOTE:
Before installing a spark plug, clean the gas-
ket surface and plug surface.
Finger-tighten a the spark plug before torqu-
ing to specification b.
T R..13 Nm (1.3 m · kg, 9.4 ft · lb)

3 - 20
INSP
ADJ
BATTERY INSPECTION AND CHARGING
WARNING
Batteries generate explosive hydrogen gas
and contain electrolyte which is made of
poisonous and highly caustic sulfuric acid.
Therefore, always follow these preventive
measures:
Wear protective eye gear when handling
or working near batteries.
Charge batteries in a well-ventilated area.
Keep batteries away from fire, sparks or
open flames (e.g., welding equipment,
lighted cigarettes).
DO NOT SMOKE when charging or han-
dling batteries.
KEEP BATTERIES AND ELECTROLYTE
OUT OF REACH OF CHILDREN.
Avoid bodily contact with electrolyte as it
can cause severe burns or permanent eye
injury.
FIRST AID IN CASE OF BODILY CONTACT:
EXTERNAL
Skin — Wash with water.
Eyes — Flush with water for 15 minutes
and get immediate medical attention.
INTERNAL
Drink large quantities of water or milk fol-
lowed with milk of magnesia, beaten egg
or vegetable oil. Get immediate medical
attention.
CAUTION:
Charging time, charging amperage and
charging voltage for an MF battery are dif-
ferent from those of conventional batteries.
The MF battery should be charged as
explained in the charging method illustra-
tions. If the battery is overcharged, the
electrolyte level will drop considerably.
Therefore, take special care when charging
the battery.
BATTERY INSPECTION AND CHARGING

4 - 6
ENGCARBURETOR
EC464600
Float
1. Inspect:
Float 1
Damage → Replace.
ASSEMBLY AND INSTALLATION
Carburetor
1. Install:
Pilot air screw 1
Note the following installation points:
Screw in the pilot air screw until it is lightly
seated.
Back out it by the specified number of
turns.
Pilot air screw:
1-3/4 turns out
2. Install:
Throttle valve 1
Starter plunger 2
NOTE:
Align the slit a of the throttle valve with the tab
b of the carburetor top.
FUEL LEVEL ADJUSTMENT
WARNING
Gasoline (fuel) and its vapors are highly
flammable and explosive. Keep away from
sparks, cigarettes, flames or other sources
of ignition.

4 - 19
ENGVALVES AND VALVE SPRINGS
2. Lap:
Valve face
Valve seat
NOTE:
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and
valve face should be lapped.
Lapping steps:
Apply a coarse lapping compound to the
valve face.
CAUTION:
Do not let the compound enter the gap
between the valve stem and the guide.
Apply molybdenum disulfide oil to the
valve stem.
Install the valve into the cylinder head.
Turn the valve until the valve face and
valve seat are evenly polished, then clean
off all of the compound.
NOTE:
For best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands.
Apply a fine lapping compound to the
valve face and repeat the above steps.
NOTE:
After every lapping operation be sure to
clean off all of the compound from the valve
face and valve seat.
Apply Mechanic’s blueing dye (Dykem) to
the valve face.
Install the valve into the cylinder head.
Press the valve through the valve guide
and onto the valve seat to make a clear
pattern.
Measure the valve seat width again. If the
valve seat width is out of specification,
reface and relap the valve seat.

4 - 20
ENGVALVES AND VALVE SPRINGS
ASSEMBLY AND INSTALLATION
1. Apply:
Molybdenum disulfide oil
(onto the valve stem and valve stem
seal)
2. Install:
Valve stem seats
Valves
Valve springs
Valve spring retainers
NOTE:
Make sure that each valve is installed in its
original place, also referring to the embossed
mark as follows.
Intake: “G”
Exhaust: “L”
Install the valve springs with the larger pitch
a facing upwards.
bSmaller pitch
New
3. Install:
Valve cotters
NOTE:
While compressing the valve spring with a
valve spring compressor and attachment 1
install the valve cotters.
Valve spring compressor:
YM-4019/90890-04019
4. To secure the valve cotters onto the
valve stem, lightly tap the valve tip with a
piece of wood.
CAUTION:
Hitting the valve tip with excessive force
could damage the valve.

4 - 32
ENGCLUTCH
ASSEMBLY AND INSTALLATION
Primary clutch
1. Install:
Washer 1
Nut (primary clutch) 2
NOTE:
Tighten the nut while holding the magneto
rotor with the sheave holder 3.
Clutch
1. Install:
Lock washer 1
Nut (clutch boss) 2
NOTE:
Use the clutch holding tool 3 to hold the clutch
boss.
ÅFor USA and CDN
ıExcept for USA and CDN
2. Bend:
Lock washer tab
Sheave holder:
YS-1880-A/90890-01701
Clutch holding tool:
YM-91042/90890-04086
T R..50 Nm (5.0 m · kg, 36 ft · lb)
New
T R..70 Nm (7.0 m · kg, 50 ft · lb)
Åı
Clutch release adjustment
1. Adjust:
Clutch release
Adjustment steps:
Loosen the locknut 1.
Turn in the adjuster 2 until it is lightly
seated.
Turn out by 1/8 turn.
Tighten the locknut.
T R..
Locknut:
8 Nm (0.8 m • kg, 5.8 ft • lb)