engine YAMAHA TTR90 2006 Service Manual

3 - 6
INSP
ADJ
ENGINE OIL LEVEL INSPECTION
1. Start the engine, warm it up for several
minutes, and then turn off the engine 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 È:
Yamalube 4 (10W-30) or SAE
10W-30 type SE/SF/SG motor
oil
At 5 °C (40 °F) or higher É:
Yamalube 4 (20W-40) or SAE
20W-40 type SE/SF/SG motor
oil010 30 50 70
90110
130
-20
-10010
20 30 40
50
È
É
˚C ˚F
ENGINE OIL LEVEL INSPECTION

3 - 7
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 sev-
eral 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.
Recommended oil:
Refer to the following chart for
selection of oils which are
suited to the atmospheric
temperatures.
Recommended engine oil classifi-
cation:
API STANDARD:
API “SE/SF/SG” or higher grade
(Designed primarily for
motorcycles)
a
b
ENGINE OIL REPLACEMENT
1. Start the engine, warm it up for several
minutes, and then turn off the engine 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.

3 - 8
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 - 9
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 throt-
tle stop screw
1 in
a.
To decrease idle speed
→ Turn the throt-
tle 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 - 11
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 portion
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 - 14
INSP
ADJ
DRIVE CHAIN SLACK ADJUSTMENT
5. Install:
Drive chain 1
Joint 2
Master link clip 3
CAUTION:
Be sure to install the master link clip to the
direction as shown.
aTurning direction
New
6. Lubricate:
Drive chain
Drive chain lubricant:
SAE 10W-30 motor oil or
suitable chain lubricants
DRIVE CHAIN SLACK ADJUSTMENT
1. Elevate the rear wheel by placing the suit-
able 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 - 15
INSP
ADJ
FRONT FORK INSPECTION
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.
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)
13 a2
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.

3 - 16
INSP
ADJREAR SHOCK ABSORBER INSPECTION/
REAR SHOCK ABSORBER SPRING PRELOAD ADJUSTMENT
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 suit-
able 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.
4. To stiffen the spring preload, install the cir-
clip 1 into the groove a. To soften the
spring preload, install the circlip into the
groove b.
NOTE:
Do not spread the circlip too much.
Standard installation position:
Groove b
5. Install:
Spring guide 1
NOTE:
While compressing the spring, install the
spring guide.

3 - 18
INSP
ADJWHEEL INSPECTION/
STEERING HEAD INSPECTION AND ADJUSTMENT
EC36T000
WHEEL INSPECTION
1. Inspect:
Wheel runout
Elevate the wheel and turn it.
Abnormal runout → Replace.
2. Inspect:
Bearing free play
Exist play → Replace.
STEERING HEAD INSPECTION AND
ADJUSTMENT
1. Elevate the front wheel by placing a suit-
able stand under the engine.
2. Check:
Steering shaft
Grasp the bottom of the forks and gently
rock the fork assembly back and forth.
Free play → Adjust steering head.
3. Check:
Steering smooth action
Turn the handlebar lock to lock.
Unsmooth action → Adjust steering ring
nut.
4. Adjust:
TT-R90
Steering ring nut
Steering ring nut adjustment steps:
Remove the front fender 1.
Remove the handlebar and handle crown.
Loosen the ring nut 2 using the ring nut
wrench 3.

3 - 23
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)