ad blue YAMAHA TTR90 2003 Owners Manual

4 - 18
ENGVALVES AND VALVE SPRINGS
Valve spring
1. Measure:
Valve spring free length a
Out of specification → Replace.
2. Measure:
Spring tilt a
Out of specification → Replace.
Free length (valve spring):
Intake:
32.45 mm (1.28 in)
: 26.9 mm (1.06 in)
Exhaust:
32.45 mm (1.28 in)
: 26.9 mm (1.06 in)
Spring tilt limit:
Intake:
2.5˚/1.4 mm (0.06 in)
Exhaust:
2.5˚/1.4 mm (0.06 in)
Valve seat
1. Measure:
Valve seat width a
Out of specification → Reface the valve
seat.
Valve seat width:
Intake:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
: 1.6 mm (0.0630 in)
Exhaust:
0.9 ~ 1.1 mm (0.0354 ~ 0.0433 in)
: 1.6 mm (0.0630 in)
Measurement steps:
Apply Mechanic’s blueing dye (Dykem) b
to the valve face.
Install the valve into the cylinder head.
Press the valve through the valve guide
and onto the valve seat to make a clear
pattern.
Measure the valve seat width. Where the
valve seat and valve face made contact,
blueing will have been removed.
If the valve seat is too wide, too narrow, or
the seat is not centered, the valve seat
must be refaced.

4 - 19
ENGVALVES AND VALVE SPRINGS
2. Lap:
Valve face
Valve seat
NOTE:
After refacing the valve seat or replacing the
valve and valve guide, the valve seat and
valve face should be lapped.
Lapping steps:
Apply a coarse lapping compound to the
valve face.
CAUTION:
Do not let the compound enter the gap
between the valve stem and the guide.
Apply molybdenum disulfide oil to the
valve stem.
Install the valve into the cylinder head.
Turn the valve until the valve face and
valve seat are evenly polished, then clean
off all of the compound.
NOTE:
For best lapping results, lightly tap the valve
seat while rotating the valve back and forth
between your hands.
Apply a fine lapping compound to the
valve face and repeat the above steps.
NOTE:
After every lapping operation be sure to
clean off all of the compound from the valve
face and valve seat.
Apply Mechanic’s blueing dye (Dykem) to
the valve face.
Install the valve into the cylinder head.
Press the valve through the valve guide
and onto the valve seat to make a clear
pattern.
Measure the valve seat width again. If the
valve seat width is out of specification,
reface and relap the valve seat.

4 - 25
ENG

CYLINDER AND PISTON
Piston pin
1. Inspect:

Piston pin
Blue discoloration/grooves
→

Replace, then inspect the lubrication
system.
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)

6 - 1
–+ELEC

12
3
456
7
0
98

A
B
F
EC
D

ELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC600000
ELECTRICAL
EC610000
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC611000
ELECTRICAL COMPONENTS
1
Main switch
2
“ENGINE STOP”
switch
3
Thermo switch
4
Ignition coil
5
CDI unit
6
Battery
7
Rectifier/regulator
8
Neutral switch
9
CDI magneto
0
Carburetor heater
A
Starter relay
B
Fuse
C
Start switch
D
Spark plug
E
Starter motor
F
Starting circuit cut-off
relay
COLOR CODE
B ...................... Black
Br .................... Brown
G ..................... Green
O ..................... Orange
R ..................... Red
Sb .................... Sky blue
W ..................... White
Y ...................... Yellow
EC612000
WIRING DIAGRAM
G/WB/RW/LW/RBr G
RW
B/WBr BRB/WBBrR
B/WB BB
BR/WBr B
GG/W
B/W
B/W
BrB/RWWOO
B
BW/LY/RR
W
B
B
R
W/RY/R
OFF RUNB
Y/R
Y
Y
OBO BY/RYB B
Sb
W W
Sb
ON OFF
OFFON
Y
BB
Y/R
Br
Br
B
B
R
RR
R
B
R/WR/W
R/WR/W
R/W
Sb
Sb
RB
R/WB R
Y/RRB W
B/WB
R/W
R/W
R/W
Sb
9
8
1 B5
4
D
2 3
=A
E 6
C
F 7

B/R ................... Black/Red
B/W .................. Black/White
G/W.................. Green/White
R/W .................. Red/White
W/L .................. White/Blue
W/R .................. White/Red
Y/R ................... Yellow/Red

6 - 8
–+ELEC
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
Couplers and leads connection
Rust/dust/looseness/short-circuit →
Repair or replace.
STARTER MOTOR OPERATION
1. Connect the positive battery terminal 1
and starter motor lead 2 with a jumper
lead 3.
Not operate → Repair or replace the
starter motor.
WARNING
A wire that is used as a jumper lead must
have at least the same capacity or more
as that of the a battery lead, otherwise the
jumper lead may burn.
This check is likely to produce sparks,
therefore make sure nothing flammable is
in the vicinity.
STARTING CIRCUIT CUT-OFF RELAY
INSPECTION
1. Remove:
Starting circuit cut-off relay
2. Inspect:
Starting circuit cut-off relay conduct
Use 12 V battery.
Battery (+) lead → Red/White lead 1
Battery (–) lead → Sky blue lead 2
Tester (+) lead → Red/White lead 3
Tester (–) lead → Red/White lead 4
R/W
3R/W
4Tester selec-
tor position
Connected
to battery
Ω × 1Not
connected
to battery
2 4
3
1
ELECTRIC STARTING SYSTEM

6 - 9
–+ELEC
STARTER RELAY INSPECTION
1. Remove:
Starter relay
2. Inspect:
Starter relay conduct
Use 12 V battery.
Continuous while not connected to the battery
→ Replace.
Not continuous while connected to the battery
→ Replace.Battery (+) lead →
Starter relay terminal 1
Battery (–) lead →
Starter relay terminal 2
Tester (+) lead →
Starter relay terminal 3
Tester (–) lead →
Starter relay terminal 4
Ter-
minal
3
Ter-
minal
4Tester selec-
tor position
Connected
to battery
Ω × 1Not
connected
to battery
NEUTRAL SWITCH INSPECTION
1. Inspect:
Neutral switch conduct
No continuous while in neutral → Replace.
Continuous while in gear → Replace. Tester (+) lead → Sky blue lead 1
Tester (–) lead → Black lead 2
Sb
1B
2Tester selec-
tor position
NEU-
TRAL
Ω × 1
IN
GEAR
WSb
YB
1
2
ELECTRIC STARTING SYSTEM