2000 YAMAHA TTR90 engine

4 - 26
ENGCYLINDER AND PISTON
2. Position:
lTop ring
l2nd ring
lOil 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:
lPiston 1
lPiston pin 2
lPiston pin clips 3
NOTE:
lApply engine oil onto the piston pin, piston
ring and piston.
lBe sure that the arrow mark a on the piston
points to the exhaust side of the engine.
lBefore 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:
lPiston
lPiston rings
lCylinder
NOTE:
Apply a liberal coating of engine oil.
New
Cylinder
1. Install:
lCylinder 1
NOTE:
Install the cylinder with one hand while com-
pressing the piston rings with the other hand.
CAUTION:
lBe careful not to damage the timing chain
damper during installation.
lPass the timing chain through the timing
chain cavity.

4 - 27
ENGCLUTCH
CLUTCH
CRANKCASE COVER (LEFT AND RIGHT)
Extent of removal:1 Crankcase cover (left) removal2 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
1
2

4 - 41
ENGCRANKCASE AND CRANKSHAFT
CRANKCASE AND CRANKSHAFT
Extent of removal Order Part name Q’ty Remarks
CRANKCASE SEPARATION
AND CRANKSHAFT REMOVAL
Preparation for removal Seat and fuel tank
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
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.

4 - 44
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 disassembly3 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
Refer to “REMOVAL POINTS”. 2 Shift cam 1
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
1
2

4 - 46
ENG

SHIFT FORK, SHIFT CAM AND TRANSMISSION
EC4H3000
REMOVAL POINTS
Shift fork, shift cam and transmission
1. Remove:
l
Shift forks
l
Shift cam
l
Drive axle assembly
l
Main axle assembly
NOTE:

l
Tap lightly on the transmission drive axle and
shift cam with a soft hammer to remove.
l
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:
l
Main axle assembly
1

l
Drive axle assembly
2

2. Install:
l
Shift fork 1 “L”
1

l
Shift fork 2 “R”
2

l
Shift cam
3

l
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:
l
Shifter operation
l
Transmission operation
Unsmooth operation
®
Repair.

5 - 1
CHAS

EC500000
CHASSIS
FRONT WHEEL AND REAR WHEEL
EC598000
FRONT WHEEL AND FRONT BRAKE
FRONT WHEEL AND REAR WHEEL
Extent of removal:
1
Front wheel removal
2
Wheel bearing removal
3
Brake shoe plate assembly removal and disassembly
Extent of removal Order Part name Q’ty Remarks
FRONT WHEEL REMOVAL
Preparation for removal Hold the machine by placing the
suitable stand under the engine.
1 Bolt (brake cable holder) 1 Only loosening.
2 Brake cable 1 Disconnect at the lever side.
3 Wheel axle nut 1
4 Front wheel axle 1
5 Front wheel 1
6 Collar set 1
7 Brake shoe plate assembly 1
8 Oil seal 1
9Bearing
2Refer to “REMOVAL POINTS”.
WARNING
Support the machine securely so there is nodanger of it falling over.
2
31
3

5

5 - 3
CHAS

FRONT WHEEL AND REAR WHEEL
EC598100
REAR WHEEL AND REAR BRAKE
Extent of removal:
1
Rear wheel removal
2
Wheel bearing removal
3
Brake shoe plate assembly removal and disassembly
Extent of removal Order Part name Q’ty Remarks
REAR WHEEL REMOVAL
Preparation for removal Hold the machine by placing the
suitable stand under the engine.
1 Brake rod 1
2 Cotter pin 1
3 Nut (tension bar) 1
4 Bolt (tension bar) 1
5 Wheel axle nut 1
6 Rear wheel axle 1
7 Drive chain puller 2
8 Rear wheel 1
9 Collar (right) 1
10 Brake shoe plate assembly 1
WARNING
Support the machine securely so there is nodanger of it falling over.
231

5 - 6
CHAS

FRONT FORK
EC550000
FRONT FORK
Extent of removal:
1
Front fork removal
Extent of removal Order Part name Q’ty Remarks
FRONT FORK REMOVAL
Preparation for removal Hold the machine by placing the
suitable stand under the engine.
Front wheel Refer to “FRONT WHEEL AND FRONT
BRAKE” section.
Handlebar Refer to “HANDLEBAR” section.
Front fender
1 Brake cable holder 1
2 Cap bolt 1
3 Adjuster 1 Only loosening.
4 Pinch bolt (under bracket) 1 Only loosening.
5 Front fork 1
WARNING
Support the machine securely so there is nodanger of it falling over.
1