2002 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 ....................................... 4-39
CRANKCASE AND CRANKSHAFT ....... 4-41
SHIFT FORK, SHIFT CAM AND
TRANSMISSION ..................................... 4-44
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
CARBURETOR HEATING SYSTEM ........ 6-6
MAINTENANCE RECORD ....................... 6-9

2 - 16
SPECCABLE ROUTING DIAGRAM
CABLE ROUTING DIAGRAM
1Crankcase breather hose
2Wire harness
3CDI magneto lead
4Starter cable
5Carburetor heating lead
6Engine stop switch lead
7Thermo switch
8Thermo switch lead
9Spark plug lead
0Throttle cableACable holder
BFuel tank breather hose
CBrake cable
After fastening the starter cable, CDI magneto lead, wire harness and
thermo switch lead, cut off any excess from the plastic locking tie end.
õPass the ignition coil lead through the lead guide.
‚Fasten the engine stop switch lead with the plastic bands.
ëPass the brake cable through the cable guides.
12345
9
0
B A
6
C 1
õ
‚
ë
ë
A
A
67
8
20 ~ 30 mm
(0.79 ~ 1.18 in)

–+ELEC
6 - 6
CARBURETOR HEATING SYSTEM
CARBURETOR HEATING SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning carburetor heating system.
NOTE:
lRemove the following parts before inspection.
1) Seat
2) Fuel tank
lUse 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. Source 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 - 7
–+ELECCARBURETOR HEATING SYSTEM
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
lCouplers and leads connection
Rust/dust/looseness/short-circuit ®
Repair or replace.
CDI MAGNETO INSPECTION
1. Inspect:
lSource coil resistance
Refer to “IGNITION SYSTEM” section.
THERMO SWITCH INSPECTION
1. Inspect:
lThermo switch operation
Faulty operation ® Replace.
Inspection steps:
lRemove the thermo switch.
lConnect the pocket tester to the thermo
switch coupler as shown.
Tester (+) lead ® Black 1
Tester (–) lead ® Black 2
lImmerse the thermo switch in a container
filled with water 3.
lPlace a thermometer 4 in the water.
lSlowly heat the water, and then let it cool to
the specified temperature as indicated in
the table.
lCheck the thermo switch for continuity at
the temperatures indicated in the table.

6 - 8
–+ELECCARBURETOR HEATING SYSTEM
The thermo switch circuit is open.
õThe thermo switch circuit is closed.
Test step Water temperature Continuity
1Less than 23 ± 3 ˚C
(73.4 ± 5.4 ˚F)YES
2More than 23 ± 3 ˚C
(73.4 ± 5.4 ˚F)NO
3More than 12 ± 4 ˚C
(53.6 ± 7.2 ˚F)NO
4Less than 12 ± 4 ˚C
(53.6 ± 7.2 ˚F)YES
Test steps 1 & 2: Heating phase
Test steps 3 & 4: Cooling phase
WARNING
lHandle the thermo switch with special
care.
lNever subject the thermo switch to
strong shocks. If the thermo switch is
dropped, replace it.
lCheck the thermo switch operation.
CARBURETOR HEATER INSPECTION
1. Inspect:
lCarburetor 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 W at
20˚C (68 ˚F)W ´ 1