engine YAMAHA TTR90 2006 Workshop Manual

4 - 1
ENG
ENGINE
CARBURETOR
Extent of removal:
1 Carburetor removal
Extent of removal Order Part name Q’ty Remarks
CARBURETOR REMOVAL
Preparation for removal Fuel tank
1 Clamp (air filter joint) 1 Loosen the screw (air filter joint).
2 Carburetor heater lead 1
3 Air vent hose 1
4 Fuel hose 1
5Bolt 2
6 Carburetor assembly 1
7O-ring 2
8Spacer 1
9 Carburetor top 1
10 Starter plunger assembly 1
1
CARBURETOR

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ENGCYLINDER HEAD
4. Remove:
Cylinder head
NOTE:
Loosen the bolts and nuts in their proper
loosening sequence.
Start by loosening each bolt and nut 1/2 turn
until all are loose.
ASSEMBLY AND INSTALLATION
1. Install:
Cylinder head
2. Tighten:
Nuts
Bolts
NOTE:
Apply the engine oil on the contact surfaces
of the nuts, bolts and copper washers.
Follow the numerical order shown in the illus-
tration. Tighten the bolts and nuts in two
stages.
T R..22 Nm (2.2 m · kg, 16 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
3. Install:
Camshaft sprocket 1
Installation steps:
Turn the crankshaft counterclockwise until
the “I” mark a on the rotor is aligned with
the stationary pointer b on the crankcase
cover.
Align the “I” mark c on the camshaft
sprocket with the stationary pointer d on
the cylinder head.
Fit the timing chain 2 onto camshaft
sprocket and install the camshaft sprocket
on the camshaft.
NOTE:
When installing the camshaft sprocket, keep
the timing chain as tense as possible on the
exhaust side.

4 - 14
ENGCAMSHAFT AND ROCKER ARMS
REMOVAL POINTS
Rocker arm shaft
1. Remove:
Rocker arm shafts
NOTE:
Use a slide hammer bolt 1 and weight 2 to
slide out the rocker arm shafts.
Slide hammer set:
YU-1083-A
Slide hammer bolt:
90890-01085
Weight:
90890-01084
INSPECTION
Camshaft
1. Measure:
Cam lobes length a and b
Out of specification → Replace.
Cam lobes length limit:
Intake:
a 25.398 mm (0.9999 in)
b 21.004 mm (0.8269 in)
Exhaust:
a 25.256 mm (0.9943 in)
b 21.017 mm (0.8274 in)
ASSEMBLY AND INSTALLATION
1. Apply:
Molybdenum disulfide oil
(onto the camshaft cam lobe)
Engine oil
(onto the camshaft bearing)
2. Install:
Camshaft 1

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ENGCYLINDER AND PISTON
Piston pin
1. Inspect:
Piston pin
Blue discoloration/grooves →
Replace, then inspect the lubrication sys-
tem.
2. Measure:
Piston pin outside diameter
Piston pin bore inside diameter
ASSEMBLY AND INSTALLATION
Piston
1. Install:
Piston rings
(onto the piston)
NOTE:
Be sure to install the piston rings so that the
manufacturer’s marks or numbers are
located on the upper side of the rings.
Lubricate the piston and piston rings liberally
with engine oil. Measurement steps:
Measure the piston pin outside diameter
a.
If out of specification, replace the piston
pin.
Outside diameter (piston pin):
12.996 ~ 13.000 mm
(0.5117 ~ 0.5118 in)
:12.976 mm (0.5109 in)
Measure the piston inside diameter b.
If out of specification, replace the piston.
Inside diameter (piston):
13.002 ~ 13.013 mm
(0.5119 ~ 0.5123 in)
: 13.045 mm (0.5136 in)

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ENGCYLINDER AND PISTON
2. Position:
Top ring
2nd ring
Oil ring
Offset the piston ring end gaps as shown.
aTop ring end
bOil ring end (lower)
cOil ring end (upper)
d2nd ring end
3. Install:
Piston 1
Piston pin 2
Piston pin clips 3
NOTE:
Apply engine oil onto the piston pin, piston
ring and piston.
Be sure that the arrow mark
a on the piston
points to the exhaust side of the engine.
Before installing the piston pin clip, cover the
crankcase with a clean rag to prevent the
piston pin clip from falling into the crankcase.
4. Lubricate:
Piston
Piston rings
Cylinder
NOTE:
Apply a liberal coating of engine oil.
New
Cylinder
1. Install:
Dowel pins
Gasket
Cylinder 1
NOTE:
Install the cylinder with one hand while com-
pressing the piston rings with the other hand.
CAUTION:
Be careful not to damage the timing chain
damper during installation.
Pass the timing chain through the timing
chain cavity.
New

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ENGCLUTCH
CLUTCH
CRANKCASE COVER (LEFT AND RIGHT)
Extent of removal:
1 Crankcase cover (left) removal
2 Crankcase cover (right) removal
Extent of removal Order Part name Q’ty Remarks
CRANKCASE COVER (LEFT
AND RIGHT) REMOVAL
Preparation for removal Drain the engine oil. Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
1 Shift pedal 1
2 Drive sprocket cover 1
3 Crankcase cover (left) 1
4 Gasket 1
5 Dowel pin 2
6 Clutch adjusting screw 1
7 Kick crank 1
8 Crankcase cover (right) 1
9 Gasket 1
10 Dowel pin 2
2
1

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ENGCDI MAGNETO AND STARTER CLUTCH (TT-R90E)
3. Install:
Spring 1
Spring cap 2
Pin 3
4. Install:
Shim 1
Starter wheel gear 2
Starter idle gear 3
Shaft 4
NOTE:
Apply the molybdenum disulfide oil on the
starter wheel gear inner circumference.
Apply the engine oil on the starter idle gear
inner circumference and on the shaft outer
circumference.
12
3
123
5. Install:
Woodruff key 1
Rotor 2
NOTE:
Clean the tapered portion of the crankshaft
and the magneto hub.
When installing the magneto rotor, make
sure the woodruff key is properly seated in
the key way of the crankshaft.
6. Tighten:
Nut (magneto) 1
NOTE:
Tighten the nut (magneto) 1 while holding the
magneto 2 with a sheave holder 3.
7. Install:
Crankcase cover (left)
NOTE:
Pass the starter motor lead 1 and neutral
switch lead 2 into the crankcase cover
groove as shown.
Fasten the starter motor lead with the clamp
3.
Sheave holder:
YS-1880-A/90890-01701
T R..48 Nm (4.8 m · kg, 35 ft · lb)
2
1
1
3

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ENGCRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
Extent of removal Order Part name Q’ty Remarks
CRANKCASE SEPARATION
AND CRANKSHAFT REMOVAL
Preparation for removal Seat, fuel tank and rear fender
Exhaust pipe
Air filter case
Carburetor Refer to “CARBURETOR” section.
Drain the engine oil Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
Engine guard and drive sprocket
Engine assembly From the chassis.
Cylinder head Refer to “CYLINDER HEAD” section.
Cylinder and piston Refer to “CYLINDER AND PISTON” sec-
tion.
Clutch housing and clutch carrier Refer to “CLUTCH” section.
Kick axle assembly Refer to “KICK AXLE” section.

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ENGSHIFT FORK, SHIFT CAM AND TRANSMISSION
SHIFT FORK, SHIFT CAM AND TRANSMISSION
Extent of removal:
1 Shift fork, shift cam, main axle and drive axle removal
2 Main axle disassembly
3 Drive axle disassembly
Extent of removal Order Part name Q’ty Remarks
SHIFT FORK, SHIFT CAM
TRANSMISSION REMOVAL
Preparation for removal Engine assembly
Separate the crankcase. Refer to “CRANKCASE AND CRANK-
SHAFT”section.
1 Guide bar 1
2Shift cam 1
Refer to “REMOVAL POINTS”. 3 Shift fork 2 “R”1
4 Shift fork 1 “L”1
5 Drive axle assembly 1
6 Main axle assembly 1
7 2nd pinion gear 1
8 Circlip 1
9 Washer 1
2
1

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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.