2003 YAMAHA TTR90 engine

3 - 4
INSP
ADJ

AIR FILTER CLEANING
1. Install:

Air scoop (right)
1

2. Install:

Air filter case cover
1

3. Clean:

Air filter element
Clean them with solvent.
NOTE:

After cleaning, remove the remaining solvent
by squeezing the element.
CAUTION:


Do not twist the element when squeezing
the element.

Leaving too much of solvent in the ele-
ment may result in poor starting.
4. Inspect:

Air filter element
Damage
→
Replace.
5. Apply:

Foam-air-filter oil or engine mixing oil
To the element.
NOTE:

Squeeze out the excess oil. Element should be
wet but not dripping.
6. Install:

Air filter element
1

NOTE:

Align the projection
a
on the air filter case with
the hole
b
in the air filter element.
7. Install:

Air filter case cover
8. Install:

Air scoop (right)

3 - 5
INSP
ADJ

ENGINE OIL LEVEL INSPECTION
1. Start the engine, warm it up for several
minutes and wait for five minutes.
2. Place the machine on a level place and
hold it up on upright position by placing
the suitable stand under the engine.
3. Remove:

Dipstick
1
4. Check:

Oil level
Oil level should be between maximum
a
and minimum
b
marks.
Oil level is low
→
Add oil to proper
level.
NOTE:

When inspecting the oil level, do not screw the
dipstick into the oil tank. Insert the gauge
lightly.
(For USA and CDN)
CAUTION:


Do not add any chemical additives.
Engine oil also lubricates the clutch and
additives could cause clutch slippage.

Do not allow foreign material to enter the
crankcase.
Recommended oil:
At –10 ˚C (10 ˚F) or higher
Å
:
Yamalube 4 (10W-30) or SAE
10W-30 type SE/SF motor oil
At 5 ˚C (40 ˚F) or higher
ı
:
Yamalube 4 (20W-40) or SAE
20W-40 type SE/SF motor oil
010 30 50 70
90110
130
-20
-10010
20 30 40
50
Å
ı
˚C ˚F

ENGINE OIL LEVEL INSPECTION

3 - 6
INSP
ADJ

ENGINE OIL REPLACEMENT
(Except for USA and CDN)
CAUTION:


Do not add any chemical additives or use
oils with a grade of CD a or higher.
Do not use oils labeled “ENERGY CON-
SERVING II” b or higher. Engine oil also
lubricates the clutch and additives could
cause clutch slippage.
Do not allow foreign materials to enter the
crankcase.
5. Install:
Dipstick
6. Start the engine and let it warm up for
several minutes.
7. Turn off the engine and inspect the oil
level once again.
NOTE:
Wait a few minutes until the oil settles before
inspecting the oil level.
ENGINE OIL REPLACEMENT
1. Start the engine and warm it up for sev-
eral minutes and wait for five minutes.
2. Place the machine on a level place and
hold it on upright position by placing the
suitable stand under the engine.
3. Place a suitable container under the
engine.
4. Remove:
Dipstick 1
Drain bolt (with gasket) 2
Drain the crankcase of its oil.
Recommended oil:
Refer to the following chart for
selection of oils which are suited
to the atmospheric temperatures.
Recommended engine oil classi-
fication:
API STANDARD:
API “SE/SF” or higher grade
(Designed primarily for motor-
cycles)
a
b

3 - 7
INSP
ADJ
PILOT AIR SCREW ADJUSTMENT
5. Install:
Gasket
Drain bolt
New
T R..20 Nm (2.0 m · kg, 14 ft · lb)
6. Fill:
Crankcase
Oil quantity:
Periodic oil change:
0.8 L (0.70 Imp qt, 0.85 US qt)
7. Install:
Dipstick
8. Inspect:
Engine (for oil leaks)
Oil level
Refer to “ENGINE OIL LEVEL INSPEC-
TION”.
PILOT AIR SCREW ADJUSTMENT
1. Adjust:
Pilot air screw 1
Adjusting steps:
Screw in the pilot air screw until it is lightly
seated.
Back out by the specified number of turns.
Pilot air screw:
1-3/4 turns out

3 - 8
INSP
ADJIDLE SPEED ADJUSTMENT/
VALVE CLEARANCE ADJUSTMENT
IDLE SPEED ADJUSTMENT
1. Start the engine and thoroughly warm it
up.
2. Attach:
Inductive tachometer
To spark plug lead.
3. Adjust:
Idle speed
VALVE CLEARANCE ADJUSTMENT
NOTE:
The valve clearance should be adjusted
when the engine is cool to the touch.
The piston must be at Top Dead Center
(T.D.C.) on compression stroke to check or
adjust the valve clearance.
1. Remove:
Air scoop (right) 1
Air filter case 2
2. Remove:
Spark plug
Tappet cover (intake side) 1
Tappet cover (exhaust side) 2 Adjustment steps:
Adjust the pilot screw.
Refer to “PILOT AIR SCREW ADJUST-
MENT” section.
Turn the throttle stop screw 1 until the
engine runs at the lowest possible speed.
To increase idle speed →
Turn the throttle stop screw 1 in a.
To decrease idle speed →
Turn the throttle stop screw 1 out b.
Inductive tachometer:
YU-8036-B/90890-03113
Engine idling speed:
1,400 ~ 1,600 r/min
3. Remove:
Timing plug 1
Crankshaft end cover 2
O-rings

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 - 12
INSP
ADJ
DRIVE CHAIN SLACK ADJUSTMENT
DRIVE CHAIN SLACK ADJUSTMENT
1. Elevate the rear wheel by placing the
suitable stand under the engine.
2. Check:
Drive chain slack a
In the center between the drive axle
and rear wheel axle.
Out of specification → Adjust.
NOTE:
Before checking and/or adjusting, rotate the
rear wheel through several revolutions and
check the slack several times to find the tight-
est point. Check and/or adjust chain slack with
rear wheel in this “tight chain” position.
Drive chain slack:
40 ~ 53 mm (1.6 ~ 2.1 in)
3. Adjust:
Drive chain slack
Drive chain slack adjustment steps:
Loosen the wheel axle nut 1 and locknuts
2.
Adjust chain slack by turning the adjusters
3.
To tighten →Turn adjuster 3 clockwise.
To loosen →Turn adjuster 3 counter-
clockwise and push wheel
forward.
Turn each adjuster exactly the same
amount to maintain correct axle alignment.
(There are marks a on each side of chain
puller alignment.)
NOTE:
Turn the adjuster so that the chain is in line
with the sprocket, as viewed from the rear.
CAUTION:
Too small chain slack will overload the
engine and other vital parts; keep the
slack within the specified limits.
13 a2

3 - 13
INSP
ADJFRONT FORK INSPECTION/REAR SHOCK ABSORBER INSPECTION/
REAR SHOCK ABSORBER SPRING PRELOAD ADJUSTMENT
Tighten the wheel axle nut while pushing
down the drive chain.
T R..
Axle nut:
60 Nm (6.0 m • kg, 43 ft • lb)
Tighten the locknuts.
T R..
Locknut:
7 Nm (0.7 m • kg, 5.1 ft • lb)
EC36C000
FRONT FORK INSPECTION
1. Inspect:
Front fork smooth action
Operate the front brake and stroke the
front fork.
Unsmooth action/oil leakage → Repair
or replace.
EC36K000
REAR SHOCK ABSORBER INSPECTION
1. Inspect:
Swingarm smooth action
Abnormal noise/unsmooth action →
Grease the pivoting points or repair the
pivoting points.
Damage/oil leakage → Replace.
REAR SHOCK ABSORBER SPRING
PRELOAD ADJUSTMENT
1. Elevate the rear wheel by placing the
suitable stand under the engine.
2. Remove:
Rear shock absorber
Refer to “SWINGARM” section in the
CHAPTER 5.
3. Remove:
Spring guide 1
NOTE:
While compressing the spring, remove the
spring guide.