2000 YAMAHA YZ426F ignition

3 - 4
INSP
ADJ

PRE-OPERATION INSPECTION AND MAINTENANCE
EC320000
PRE-OPERATION INSPECTION AND MAINTENANCE
Before riding for break-in operation, practice or a race, make sure the machine is in good operating
condition.
Before using this machine, check the following points.
EC321000
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
CoolantCheck that coolant is filled up to the radiator filler cap.
Check the cooling system for leakage.P.3-5 ~ 9
FuelCheck that a fresh gasoline is filled in the fuel tank. Check the
fuel line for leakage.P.1-12
Engine oilCheck that the oil level is correct. Check the crankcase and
frame oil line for leakage.P.3-13 ~ 17
Gear shifter and clutchCheck that gears can be shifted correctly in order and that the
clutch operates smoothly.P.3-9
Throttle grip/HousingCheck that the throttle grip operation and free play are correctly
adjusted. Lubricate the throttle grip and housing, if necessary.P.3-10 ~ 11
Brakes Check the play of front brake and effect of front and rear brake. P.3-24 ~ 30
ChainCheck chain slack and alignment. Check that the chain is lubri-
cated properly.P.3-31 ~ 33
WheelsCheck for excessive wear and tire pressure. Check for loose
spokes and have no excessive play.P.3-41 ~ 42
SteeringCheck that the handlebar can be turned smoothly and have no
excessive play.P.3-42 ~ 43
Front forks and rear shock
absorberCheck that they operate smoothly and there is no oil leakage. P.3-33 ~ 40
Cables (wires)Check that the clutch and throttle cables move smoothly. Check
that they are not caught when the handlebars are turned or
when the front forks travel up and down.—
Muffler Check that the muffler is tightly mounted and has no cracks. P.4-3
Sprocket Check that the driven sprocket tightening bolt is not loose. P.3-31
Lubrication Check for smooth operation. Lubricate if necessary. P.3-44
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P.1-17
Lead connectorsCheck that the CDI magneto, CDI unit, and ignition coil are con-
nected tightly.P.1-5
SettingsIs the machine set suitably for the condition of the racing course
and weather or by taking into account the results of test runs
before racing? Are inspection and maintenance completely
done?P.7-1 ~ 21

3 - 46
INSP
ADJ
IGNITION TIMING CHECK
IGNITION TIMING CHECK
1. Remove:
lTiming plug 1
2. Attach:
lTiming light
lInductive tachometer
To the spark plug lead.
3. Check:
lIgnition timing
Timing light:
YM-33277-A/90890-03141
Inductive tachometer
YU-8036-1
Engine tachometer:
90890-03113
Checking steps:
lStart the engine and let it warm up. Let the
engine run at the specified speed.
Engine speed:
1,700 ~ 1,900 r/min
lVisually check the stationary pointer a is
within the firing range b on the rotor.
Incorrect firing range ® Check rotor and
pickup assembly.
4. Install:
lTiming plug

4 - 69
ENGCDI MAGNETO
2. Install:
lWoodruff key 1
lRotor 2
NOTE:
lClean the tapered portions of the crankshaft
and rotor.
lWhen installing the woodruff key, make sure
that its flat surface a is in parallel with the
crankshaft center line b.
lWhen installing the rotor, align the keyway c
of the rotor with the woodruff key.
3. Install:
lPlain washer
lNut (rotor) 1
Use the rotor holding tool 2.
Rotor holding tool:
YU-01235/90890-01235
T R..48 Nm (4.8 m · kg, 35 ft · lb)
4. Check:
lIgnition timing
Re-check the ignition timing.
5. Connect:
lCDI magneto lead
Refer to “CABLE ROUTING DIA-
GRAM” section in the CHAPTER 2.
6. Install:
lGasket [crankcase cover (left)]
lCrankcase cover (left) 1
lHose holder (cylinder head breather
hose) 2
lScrew [crankcase cover (left)]
NOTE:
Tighten the screws in stage, using a crisscross
pattern.
New
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)

6 - 1
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ELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC600000
ELECTRICAL
EC610000
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC611000
ELECTRICAL COMPONENTS
1
“ENGINE STOP” button
2
TPS (throttle position sensor)
3
Neutral switch
4
CDI magneto
5
Ignition coil
6
Spark plug
7
CDI unit
COLOR CODE
B...................... Black
Br .................... Brown
G ..................... Green
L ...................... Blue
O ..................... Orange
P...................... Pink
R ..................... Red
EC612000
WIRING DIAGRAM
7
15
6
2 3 4
LY
BYL
B/LL
G
P
W
R
Y
B
G
BR PBrWG
RB Br WP
R/W WL/W SbW R/W Sb L/WY
B/LL Sb B OY
LB/L B OSbSb
L/WR/W
WSb
B/L
B/WB/W
B/WB/W
Br
BB
LBBY
O
N
13
4
5 2

Sb .................... Sky blue
W ..................... White
Y ...................... Yellow
B/L ................... Black/Blue
B/W .................. Black/White
L/W .................. Blue/White
R/W .................. Red/White
6

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MAP-CONTROLLED CDI UNIT
MAP-CONTROLLED CDI UNIT
A map-controlled, CDI ignition system is used in the YZ426F.
The microcomputer in the CDI unit detects the engine speed and throttle position, thus determining
the optimum ignition timing through the entire operating range. In this way, quick throttle response
can be achieved according to various riding conditions.
CDI unit
Throttle position sensor
Pickup coil AC magneto rotorIgnition coil

n
Function of Component

Component Function
TPS
(throttle position sensor)Detects throttle valve opening and inputs it into the computer in the
CDI unit as a throttle opening signal.
Pickup coil Detects signal rotor revolutions and inputs them into the computer in
the CDI unit as engine revolution signals.
CDI unit The signals of the TPS and pickup coil sensor are analyzed by the
computer in the CDI unit, which then adjusts ignition timing for the
operation requirements.
n
Principal of 3-Dimensional Control
Conventionally, ignition timing was controlled only
by engine revolutions (2-dimensional control).
However, ignition timing needs advancement also
by engine load. Thus, accurate ignition timing can
be determined by adding throttle opening to deter-
mine ignition timing (3-dimensional control).
Revolutions
Ignition timing
Throttle opening

3-D Image Map of Ignition Timing
(different from actual characteristics)

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IGNITION SYSTEM
EC620000
IGNITION SYSTEM
EC621001
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.
*marked: Only when the ignition checker is used.
NOTE:

l
Remove the following parts before inspection.
1) Seat
2) Fuel tank
l
Use the following special tools in this inspection.
Spark gap test*Clean or replace
spark plug.
Check entire ignition
system for connection.Repair or replace.
Check “ENGINE STOP”
button.Replace.
Check ignition coil. Primary coil Replace.
Secondary coilReplace.
Check CDI magneto. Pick-up coil Replace.
Source coil Replace.
Check neutral switch. Repair or replace.
Replace CDI unit.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754
Pocket tester:
YU-03112/90890-03112
No Spark
OK
OK
OK
OK
Spark
No good
No good
No good
No good
No good
No good
No good
OK

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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.
l
Spark plug cap
3

l
Spark plug
4


For USA and CDN
õ
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)

õ

EC624000
COUPLERS AND LEADS CONNECTION
INSPECTION
1. Check:
l
Couplers and leads connection
Rust/dust/looseness/short-circuit
®

Repair or replace.
EC625001
“ENGINE STOP” BUTTON INSPECTION
1. Inspect:
l
“ENGINE STOP” button conduct
No continuity while being pushed
®
Replace.
Continuity while being freed
®
Replace.
Tester (+) lead
®
Black/White lead
1

Tester (–) lead
®
Black lead
2

B/W
1
B
2
Tester selec-
tor position
PUSH IN
W

´
1
FREE

6 - 5
–+ELEC

IGNITION SYSTEM
EC626002
IGNITION COIL INSPECTION
1. Inspect:
l
Primary coil resistance
Out of specification
®
Replace.
Tester (+) lead
®
Orange lead
1

Tester (–) lead
®
Black lead
2

Primary coil
resistanceTester selector
position
0.20 ~ 0.30
W
at
20 ˚C (68 ˚F)
W

´
1
2. Inspect:
l
Secondary coil resistance
Out of specification
®
Replace.
NOTE:

When inspecting the secondary coil resis-
tance, remove the spark plug cap.
EC627011
CDI MAGNETO INSPECTION
1. Inspect:
lPick-up coil resistance
Out of specification ® Replace. Tester (+) lead ® Spark plug lead 1
Tester (–) lead ® Orange lead 2
Secondary coil
resistanceTester selector
position
9.5 ~ 14.3 kW at
20 ˚C (68 ˚F)kW ´ 1
Tester (+) lead ® Red lead 1
Tester (–) lead ® White lead 2
Pick-up coil
resistanceTester selector
position
248 ~ 372 W at
20 ˚C (68 ˚F)W ´ 100