2006 YAMAHA TTR90 check engine

3 - 4
INSP
ADJENGINE/THROTTLE CABLE ADJUSTMENT/
AIR FILTER CLEANING
EC350000
ENGINE
THROTTLE CABLE ADJUSTMENT
1. Check:
Throttle grip free play a
Out of specification → Adjust.
Throttle grip free play
a:
3 ~ 5 mm (0.12 ~ 0.20 in)
2. Adjust:
Throttle grip free play
AIR FILTER CLEANING
NOTE:
Proper air filter maintenance is the biggest key
to preventing premature engine wear and
damage.
CAUTION:
Never run the engine without the air filter
element in place; this would allow dirt and
dust to enter the engine and cause rapid
wear and possible engine damage.Throttle grip free play adjustment steps:
NOTE:
Before adjusting the throttle cable free play,
the engine idle speed should be adjusted.
Loosen the locknut 1 on throttle cable.
Turn the adjuster 2 in or out until the
specified free play is obtained.
Turning in
→ Free play is increased.
Turning out
→ Free play is decreased.
Tighten the locknut.
WARNING
After adjusting, turn the handlebar to
right and left and make sure that the
engine idling does not run faster.

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 - 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 - 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 - 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)

4 - 50
ENGSHIFT FORK, SHIFT CAM AND TRANSMISSION
EC4H3000
REMOVAL POINTS
Shift fork, shift cam and transmission
1. Remove:
Shift forks
Shift cam
Drive axle assembly
Main axle assembly
NOTE:
Tap lightly on the transmission drive axle and
shift cam with a soft hammer to remove.
Remove assembly carefully. Note the posi-
tion of each part. Pay particular attention to
the location and direction of shift forks.
ASSEMBLY AND INSTALLATION
Transmission, shift cam shift fork
1. Install:
Main axle assembly 1
Drive axle assembly 2
2. Install:
Shift fork 1 “L” 1
Shift fork 2 “R” 2
Shift cam 3
Guide bar 4
NOTE:
The embossed marks on the shift forks should
face towards the right side of the engine and
be in the following sequence: “R”, “L”.
3. Check:
Shifter operation
Transmission operation
Unsmooth operation → Repair.

–+ELEC
6 - 3
IGNITION SYSTEM
EC620000
IGNITION SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to
ignition system failure and for checking the spark plug which will not spark.
NOTE:
Remove the following parts before inspection.
1) Seat
2) Fuel tank
Use the following special tools in this inspection.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754Pocket tester:
YU-3112-C/90890-03112
Spark gap testClean or replace
spark plug.
Check entire ignition
system for connection.Repair or replace.
Check main switch.
(TT-R90E only)Replace.
Check “ENGINE STOP”
switch.Replace.
Check ignition coil. Primary coil Replace.
Secondary coil Replace.
Check CDI magneto. Pickup coil Replace.
Source coil Replace.
Replace CDI unit.
No Spark
OK
OK
OK
OK
OK
Spark
No good
No good
No good
No good
No good
No good
No good