engine oil YAMAHA YZ85 2003 Owner's Manual

4 - 40
ENG
6. Install:

Right crankcase cover 1
NOTE:
Mesh the impeller shaft gear 2 with primary
drive gear 3.
5PA41200
7. Install:

Bolt (right crankcase cover) 1

Copper washer (oil drain bolt) 2

Oil drain bolt 3

Copper washer (coolant drain bolt)
4

Coolant drain bolt 5
NOTE:
Tighten the bolts in stage, using a crisscross
pattern.
5PA41210
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
8. Install:

Kickstarter crank 1

Washer 2

Bolt (kickstarter crank) 3
NOTE:
Install the kickstarter crank closest to but not con-
tacting the pillar tube 4 and exhaust pipe 5.
5PA41220
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
9. Install:

Shift pedal 1

Bolt (shift pedal) 2
NOTE:
Install the shift pedal with the bottom of the
pedal outer diameter a as close to the center
of the engine mounting bolt 3 as possible.
5PA41230
T R..10 Nm (1.0 m · kg, 7.2 ft · lb)
KICK SHAFT, SHIFT SHAFT AND PRIMARY DRIVE GEAR

4 - 53
ENG
CRANKCASE AND CRANKSHAFT
5PAR0009
Extent of removal:
1 Crankcase separation
2 Crankshaft removal
3 Crankshaft bearing removal
Extent of removal Order Part name Q’ty Remarks
CRANKCASE AND CRANK-
SHAFT REMOVAL
Preparation for removal Engine Refer to “ENGINE REMOVAL” section.
Piston Refer to “CYLINDER HEAD, CYLINDER
AND PISTON” section.
Primary drive gear
Refer to “KICK SHAFT, SHIFT SHAFT
AND PRIMARY DRIVE GEAR” section. Kick idle gear
Stopper lever assembly
Rotor and stator Refer to “CDI MAGNETO” section.
1 Screw (crankcase) 11
2 Crankcase oil seal holder 1
3 Right crankcase 1
Use special tool.
Refer to “REMOVAL POINTS”.
4 Left crankcase 1
5 Crankshaft 1 Use special tool.
Refer to “REMOVAL POINTS”.
6 Oil seal 2
7 Bearing 2 Refer to “REMOVAL POINTS”.
2
1
3
CRANKCASE AND CRANKSHAFT

4 - 55
ENG
EC4N3401
Crankshaft bearing
1. Remove:

Bearing 1
NOTE:

Remove the bearing from the crankcase by
pressing its inner race as shown in È.

If the bearing is removed together with the
crankshaft, remove the bearing using a gen-
eral bearing puller 2 as shown in É.

Do not use the removed bearing.
5PA41630
EC4N4000
INSPECTION
Crankcase
1. Inspect:

Contacting surface a
Scratches → Replace.

Engine mounting boss b, crankcase
Cracks/damage → Replace.
5PA41650
2. Inspect:

Bearing 1
Rotate inner race with a finger.
Rough spot/seizure → Replace.
5PA41660
3. Inspect:

Oil seal 1
Damage → Replace.
5PA41670
È
É
CRANKCASE AND CRANKSHAFT

4 - 58
ENG
4. Install:

Dowel pin 1

Right crankcase 2
To left crankcase 3.
NOTE:

Turn the shift cam 4 to the position shown in
the figure so that it does not contact the
crankcase when installing the crankcase.

Fit the right crankcase onto the left crank-
case. Tap lightly on the case with soft ham-
mer.

When installing the crankcase, the connect-
ing rod should be positioned at TDC (top
dead center).
5PA41760
5PA41770
5. Install:

Clamp 1

Screw (crankcase) 2
NOTE:
Tighten the crankcase tightening screws in
stage, using a crisscross pattern.
5PA41780
T R..8 Nm (0.8 m · kg, 5.8 ft · lb)
6. Install:

Crankcase oil seal holder 1

Bolt (crankcase oil seal holder) 2
7. Remove:

Sealant
Forced out on the cylinder mating surface.
8. Apply:

Engine oil
To the crank pin, bearing, oil delivery hole
and connecting rod end washer.
9. Check:

Crankshaft and transmission operation
Unsmooth operation → Repair.
5PAR0010
T R..20 Nm (2.0 m · kg, 14 ft · lb)
CRANKCASE AND CRANKSHAFT

5 - 1
CHAS
EC500000
CHASSIS
EC590000
FRONT WHEEL AND REAR WHEEL
EC598000
FRONT WHEEL
FRONT WHEEL AND REAR WHEEL
Extent of removal:
1 Front wheel removal
2 Wheel bearing removal
3 Brake disc removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removalFRONT WHEEL REMOVAL
Hold the machine by placing the
suitable stand under the engine.
WARNING
Support the machine securely so there is no
danger of it falling over.
1 Nut (front wheel axle) 1
2 Front wheel axle 1
3 Front wheel 1
4 Collar 2
5 Oil seal 2
6 Bearing 2 Refer to “REMOVAL POINTS”.
7 Brake disc 1
2
31
3
5PA50010

5 - 2
CHAS
EC598100
REAR WHEEL
5PAR0012
Extent of removal:
1 Rear wheel removal
2 Wheel bearing removal
3 Brake disc removal
Extent of removal Order Part name Q’ty Remarks
Preparation for removalREAR WHEEL REMOVAL
Hold the machine by placing the
suitable stand under the engine.
WARNING
Support the machine securely so there is no
danger of it falling over.
1 Nut (rear wheel axle) 1
2 Rear wheel axle 1
3 Drive chain puller 2
4 Rear wheel 1 Refer to “REMOVAL POINTS”.
5 Collar 2
6 Rear wheel sprocket 1
7 Oil seal 2
8 Circlip 1
9 Bearing 2 Refer to “REMOVAL POINTS”.
10Brake disc
1
2
31
3
FRONT WHEEL AND REAR WHEEL

6 - 1
–+ELECELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC600000
ELECTRICAL
EC610000
ELECTRICAL COMPONENTS AND WIRING DIAGRAM
EC611000
ELECTRICAL COMPONENTS
1Engine stop switch
2Ignition coil
3CDI unit
4CDI magneto
5Spark plugCOLOR CODE
B ...................... Black
O ..................... Orange
B/R .................. Black/Red
B/W ................. Black/WhiteG/L................... Green/Blue
G/W ................. Green/White
W/L .................. White/Blue
W/R ................. White/Red
EC612000
WIRING DIAGRAM
5PA60010
5PA60020

6 - 2
–+ELECIGNITION 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.
*marked: Only when the ignition checker is used.
NOTE:

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

Use the following special tools in this inspection.
Dynamic spark tester:
YM-34487
Ignition checker:
90890-06754Pocket tester:
YU-3112-C/90890-03112
Spark gap test*Clean or replace
spark plug.
Check entire ignition
system for connection.Repair or replace.
Check engine stop switch. Replace.
Check ignition coil. Primary coil Replace.
Secondary coil Replace.
Check spark plug cap. Replace.
Check CDI magneto. Pickup coil Replace.
Charging coil Replace.
Replace CDI unit.
No spark
OK
OK
OK
OK
OK
Spark
No good
No good
No good
No good
No good
No good
No good

7 - 1
TUN
EC700000
TUNING
EC710000
ENGINE
Carburetor setting

The role of fuel is to cool the engine, and in
the case of a 2-stroke engine, to lubricate the
engine in addition to power generation.
Accordingly, if a mixture of air and fuel is too
lean, abnormal combustion will occur, and
engine seizure may result. If the mixture is
too rich, spark plugs will get wet with oil, thus
making it impossible to bring the engine into
full play or if the worst comes to the worst,
the engine may stall.

The richness of the air-fuel mixture required
for the engine will vary with atmospheric con-
ditions of the day and therefore, the settings
of the carburetor must be properly suited to
the atmospheric conditions (air pressure,
humidity and temperature).

Finally, the rider himself must make a test
run and check his machine for conditions
(pick-up of engine speed, road surface con-
ditions) and for the discoloration of the spark
plug(s).
After taking these into consideration, he must
select the best possible carburetor settings.
* It is advisable to make a note of settings,
atmospheric conditions, road surface condi-
tion, lap-time, etc. so that the memorandum
can be used as a reference useful for future.
Atmospheric conditions and carburetor
settings
The air density (i.e., concentration of oxygen
in the air) determines the richness or lean-
ness of the air/fuel mixture. Therefore, refer
to the above table for mixture settings.
Air temp. HumidityAir
pressure
(altitude)Mixture Setting
High High Low (high) Richer Leaner
Low Low High (low) Leaner Richer
SETTING

7 - 2
TUN
That is:

Higher temperature expands the air with its
resultant reduced density.

Higher humidity reduces the amount of oxy-
gen in the air by so much of the water vapor
in the same air.

Lower atmospheric pressure (at a high alti-
tude) reduces the density of the air.
Test run
After warming up the engine equipped with the
standard type carburetor(s) and spark plug(s),
run two or three laps of the circuit and check
the smooth operation of the engine and discol-
oration of spark plug(s).
ÈNormal
ÉOver burned (too lean)
ÊOil fouled (too rich)
Discoloration Condition of spark plug
NormalInsulator is dry and burnt
brown.
Over burned
(too lean)Insulator is whitish.
Oil fouled
(too rich)Insulator is sooty and wet.
5PA70010
È
É
Ê
SETTING