2003 YAMAHA TTR90 engine

4 - 42
ENGCDI MAGNETO AND STARTER CLUTCH
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

4 - 43
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.

4 - 46
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
2 Shift 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
1
2

4 - 48
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.

5 - 1
CHAS

EC500000
CHASSIS
FRONT WHEEL AND REAR WHEEL
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
WARNING

Support the machine securely so there is no
danger of it falling over.
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”.
2
31
3

5 - 3
CHAS

FRONT WHEEL AND REAR WHEEL
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
WARNING

Support the machine securely so there is no
danger of it falling over.
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
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
WARNING

Support the machine securely so there is no
danger of it falling over.
Preparation for removal Hold the machine by placing the
suitable stand under the engine.
Front wheel Refer to “FRONT WHEEL AND REAR
WHEEL” 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
1

5 - 9
CHASHANDLEBAR
EC5B0000
HANDLEBAR
Extent of removal:1 Handlebar removal
Extent of removal Order Part name Q’ty Remarks
HANDLEBAR REMOVAL
1 Main switch 1
2 Start switch 1
3“ENGINE STOP” switch 1
4 Brake lever cable 1 Disconnect at the lever side.
5 Brake lever 1
6 Grip cap (lower) 1
7 Grip cap (upper) 1
8 Throttle cable 1 Disconnect at the throttle side.
9 Grip (right) 1
10 Tube guide 1
11 Grip (left) 1
12 Handlebar holder (upper) 2
13 Handlebar 1
14 Handlebar holder (lower) 2
1