2003 YAMAHA TTR90 heating

CHAPTER 4
ENGINE
CARBURETOR
..........................................4-1
CYLINDER HEAD
......................................4-8
CAMSHAFT AND ROCKER ARMS
........4-13
VALVES AND VALVE SPRINGS
............4-16
CYLINDER AND PISTON
........................4-21
CLUTCH
...................................................4-27
KICK AXLE
..............................................4-33
SHIFT SHAFT
..........................................4-34
OIL PUMP
................................................4-36
CDI MAGNETO
AND STARTER CLUTCH
........................4-39
CRANKCASE AND CRANKSHAFT
........4-43
SHIFT FORK, SHIFT CAM
AND TRANSMISSION
.............................4-46
CHAPTER 5
CHASSIS
FRONT WHEEL AND REAR WHEEL
.......5-1
FRONT FORK
............................................5-6
HANDLEBAR
.............................................5-9
STEERING
...............................................5-10
SWINGARM
.............................................5-11
CHAPTER 6
ELECTRICAL
ELECTRICAL COMPONENTS
AND WIRING DIAGRAM
...........................6-1
IGNITION SYSTEM
....................................6-2
ELECTRIC STARTING SYSTEM
..............6-6
CHARGING SYSTEM
..............................6-14
CARBURETOR HEATING SYSTEM
.......6-16
MAINTENANCE RECORD
......................6-19

3 - 22
INSP
ADJ
BATTERY INSPECTION AND CHARGING
5. Charge:
Battery
(refer to the appropriate charging
method illustration)
WARNING
Do not quick charge a battery.
CAUTION:
Never remove the MF battery sealing
caps.
Do not use a high-rate battery charger
since it forces a high-amperage current
into the battery quickly and can cause
battery overheating and battery plate
damage.
If it is impossible to regulate the charging
current on the battery charger, be careful
not to overcharge the battery.
When charging a battery, be sure to
remove it from the machine. (If charging
has to be done with the battery mounted
on the machine, disconnect the negative
battery lead from the battery terminal.)
To reduce the chance of sparks, do not
plug in the battery charger until the bat-
tery charger leads are connected to the
battery.
Before removing the battery charger lead
clips from the battery terminals, be sure
to turn off the battery charger.
Make sure the battery charger lead clips
are in full contact with the battery termi-
nal and that they are not shorted. A cor-
roded battery charger lead clip may
generate heat in the contact area and a
weak clip spring may cause sparks.
If the battery becomes hot to the touch at
any time during the charging process,
disconnect the battery charger and let the
battery cool before reconnecting it. Hot
batteries can explode!
As shown in the following illustration, the
open-circuit voltage of an MF battery sta-
bilizes about 30 minutes after charging
has been completed. Therefore, wait 30
minutes after charging is completed
before measuring the open-circuit volt-
age.

–+ELEC
6 - 16
CARBURETOR HEATING SYSTEM
CARBURETOR HEATING SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning carburetor heating system.
NOTE:
Remove the following parts before inspection.
1) Seat
2) Fuel tank
Use the following special tools in this inspection.
Check entire carburetor
heating system for connec-
tion.Repair or replace.
Check thermo switch. Replace.
Check carburetor heater. Replace.
Check CDI magneto. Lighting coil Replace.
Replace rectifier/regulator.
Pocket tester:
YU-3112-C/90890-03112
OK
OK
OK
No good
No good
No good
No good
OK

6 - 17
–+ELECCARBURETOR HEATING SYSTEM
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
Couplers and leads connection
Rust/dust/looseness/short-circuit →
Repair or replace.
THERMO SWITCH INSPECTION
1. Inspect:
Thermo switch operation
Faulty operation → Replace.
Inspection steps:
Remove the thermo switch.
Connect the pocket tester to the thermo
switch coupler as shown.
Tester (+) lead → Black 1
Tester (–) lead → Black 2
Immerse the thermo switch in a container
filled with water 3.
Place a thermometer 4 in the water.
Slowly heat the water, and then let it cool to
the specified temperature as indicated in
the table.
Check the thermo switch for continuity at
the temperatures indicated in the table.
ÅThe thermo switch circuit is open.
ıThe thermo switch circuit is closed.
Test step Water temperature Continuity
1Less than 16 ± 3 ˚C
(60.8 ± 5.4 ˚F)YES
2More than 16 ± 3 ˚C
(60.8 ± 5.4 ˚F)NO
3More than 11 ± 3 ˚C
(51.8 ± 5.4 ˚F)NO
4Less than 11 ± 3 ˚C
(51.8 ± 5.4 ˚F)YES
Test steps 1 & 2: Heating phase
Test steps 3 & 4: Cooling phase

6 - 18
–+ELECCARBURETOR HEATING SYSTEM
WARNING
Handle the thermo switch with special
care.
Never subject the thermo switch to
strong shocks. If the thermo switch is
dropped, replace it.
Check the thermo switch operation.
CARBURETOR HEATER INSPECTION
1. Inspect:
Carburetor heater resistance
Out of specification → Replace.
Tester (+) probe →
Carburetor heater terminal 1
Tester (–) probe →
Carburetor heater body 2
Carburetor
heater resistanceTester selector
position
6 ~ 10 Ω at
20 ˚C (68 ˚F)Ω × 1
CDI MAGNETO INSPECTION
1. Inspect:
Lighting coil resistance
Out of specification → Replace.
Tester (+) lead → Yellow lead 1
Tester (–) lead → Black lead 2
Lighting coil
resistanceTester selector
position
0.52 ~ 0.78 Ω at
20 ˚C (68 ˚F)Ω × 1
WSb
YB
1
2