2004 YAMAHA TTR90 engine

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6 - 3
IGNITION SYSTEM
EC620000
IGNITION SYSTEM
INSPECTION STEPS
Use the following steps for checking the possibility of the malfunctioning engine being attributable to
ignition system failure and for checking the spark plug which will not spark.
NOTE:


Remove the following parts before inspection.
1) Seat
2) Fuel tank

Use the following special tools in this inspection.
Spark gap testClean or replace
spark plug.
Check entire ignition
system for connection.Repair or replace.
Check main switch.
(TT-R90E only)Replace.
Check “ENGINE STOP”
switch.Replace.
Check ignition coil. Primary coil Replace.
Secondary coil Replace.
Check CDI magneto. Pickup coil Replace.
Source coil Replace.
Replace CDI unit.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754
Pocket tester:
YU-3112-C/90890-03112
No Spark
OK
OK
OK
OK
Spark
No good
No good
No good
No good
No good
No good
OK
No good

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IGNITION SYSTEM
EC622001
SPARK GAP TEST
1. Disconnect the spark plug cap from spark
plug.
2. Connect the dynamic spark tester
1
(ignition checker
2
) as shown.

Spark plug cap
3


Spark plug
4

Å
For USA and CDN
ı
Except for USA and CDN
3. Kick the kick starter.
4. Check the ignition spark gap.
5. Start engine, and increase spark gap until
misfire occurs. (for USA and CDN only)
Minimum spark gap:
6.0 mm (0.24 in)
Å
ı
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
Couplers and leads connection
Rust/dust/looseness/short-circuit →
Repair or replace.
MAIN SWITCH INSPECTION (TT-R90E)
1. Inspect:
Main switch continuity
Check for continuity as follows:
Incorrect continuity → Replace. Tester (+) → Red lead 1
Tester (–) → Brown lead 2 Continuous
Tester (+) →
Black/White lead 3
Tester (–) → Black lead 4 Continuous
R
1Br
2B/W
3B
4Tester selec-
tor position
ON
Ω × 1
OFF
B/W
BrR
B
1
3
2
4

6 - 5
–+ELECIGNITION SYSTEM
“ENGINE STOP” SWITCH INSPECTION
TT-R90
1. Inspect:
“ENGINE STOP” switch continuity
No continuous while being pushed “” →
Replace.
Continuous while being pushed “” →
Replace.
TT-R90E
1. Inspect:
“ENGINE STOP” switch continuity
No continuous while being pushed → Replace.
Continuous while being free → Replace.
ÅTT-R90
ıTT-R90E
EC626002
IGNITION COIL INSPECTION
1. Inspect:
Primary coil resistance
Out of specification → Replace. Tester (+) lead → Black/White lead 1
Tester (–) lead → Black lead 2
B/W
1B
2Tester selec-
tor position
Ω × 1
Tester (+) lead → Black lead 1
Tester (–) lead → Black lead 2
B
1B
2Tester selec-
tor position
PUSH IN
Ω × 1
FREE
Tester (+) lead → Orange lead 1
Tester (–) lead → Black lead 2
Primary coil
resistanceTester selector
position
0.18 ~ 0.28 Ω at
20 ˚C (68 ˚F)Ω × 1
Å
B B
1
2ı

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ELECTRIC STARTING SYSTEM
(TT-R90E)
STARTING CIRCUIT CUT-OFF SYSTEM
OPERATION
If the main switch is set to “ON”, the starter
motor can only operate if the following condi-
tion is met:
The transmission is in neutral (the neutral
switch is closed).
The starting circuit cut-off relay prevents the
starter motor from operating when this condi-
tion has not been met. In this instance, the
starting circuit cut-off relay is open so current
cannot reach the starter motor. When the
above condition has been met the starting cir-
cuit cut-off relay is closed and the engine can
be started by pressing the start switch.
WHEN THE TRANSMISSION IS
IN NEUTRAL
1Battery
2Main fuse
3Main switch
4Start switch
5Starting circuit cut-off relay
6Neutral switch
7Starter relay
8Starter motor
12
M
3
7
54
6 8
ELECTRIC STARTING SYSTEM (TT-R90E)

6 - 12
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STARTER MOTOR
Extent of removal:1 Starter motor disassembly
Extent of removal Order Part name Q’ty Remarks
STARTER MOTOR REMOVAL
Preparation for removal Drain the engine oil Refer to “ENGINE OIL REPLACEMENT”
section in the CHAPTER 3.
1 Starter motor 1
STARTER MOTOR DISASSEM-
BLY
1Front bracket 1
2Ring 1
3Brush set 1
4Armature assembly 1
5Stator assembly 1
1
ELECTRIC STARTING SYSTEM (TT-R90E)

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6 - 15
CHARGING SYSTEM (TT-R90E)
EC680000
CHARGING SYSTEM (TT-R90E)
EC681001
INSPECTION STEPS
If the battery is not charged, use the following inspection steps.
*1 marked: Refer to “FUSE INSPECTION” section in the CHAPTER 3.
*2 marked: Refer to “CHECKING AND CHARGING THE BATTERY” section in the CHAPTER 3.
NOTE:
Remove the following parts before inspection.
1) Seat
2) Rear fender
3) Fuel tank
Use the following special tool in this inspection.
Pocket tester:
YU-3112-C/90890-03112Inductive tachometer:
YU-8036-B
Engine tachometer:
90890-03113
*1 Check fuse.Replace fuse and
check wire harness.
*2 Check battery. Recharge or replace.
Check each coupler and
wire connection.Repair or replace.
Check charging voltage.Charging system is
good.
Check CDI magneto. Lighting coil Replace.
Replace rectifier/regulator.
OK
OK
OK
No good
OK
No good
No good
No good
No good
OK

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–+ELECCHARGING SYSTEM (TT-R90E)
EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
Couplers and leads connection
Rust/dust/looseness/short-circuit →
Repair or replace.
CHARGING VOLTAGE INSPECTION
1. Start the engine.
2. Inspect:
Charging voltage
Out of specification → If no failure is
found in checking the source coil resis-
tance, replace the rectifier/regulator.
Tester (+) lead → Red lead 1
Tester (–) lead → Black lead 2
Charging
voltageTester selector
position
14.0 ~ 15.0 V at
5,000 r/minDCV-20
WB
R
Y/R
12
3. Inspect:
Lighting coil resistance
Out of specification → Replace.
Tester (+) lead → White lead 1
Tester (–) lead → Black lead 2
Lighting coil
resistanceTester selector
position
0.64 ~ 0.96 Ω at
20 ˚C (68 ˚F)Ω × 1
WSb
YB
1
2