2004 YAMAHA YZ85 oil

5 - 59
CHAS
HANDLING NOTE
WARNING
This rear shock absorber is provided with a
separate type tank filled with high-pressure
nitrogen gas. To prevent the danger of
explosion, read and understand the follow-
ing information before handling the shock
absorber.
The manufacturer can not be held respon-
sible for property damage or personal
injury that may result from improper han-
dling.
1. Never tamper or attempt to disassem-
ble the cylinder or the tank.
2. Never throw the rear shock absorber
into an open flame or other high heat.
The rear shock absorber may explode
as a result of nitrogen gas expansion
and/or damage to the hose.
3. Be careful not to damage any part of
the gas tank. A damaged gas tank will
impair the damping performance or
cause a malfunction.
4. Take care not to scratch the contact
surface of the piston rod with the cylin-
der; or oil could leak out.
5. Never attempt to remove the plug at
the bottom of the nitrogen gas tank. It
is very dangerous to remove the plug.
6. When scrapping the rear shock
absorber, follow the instructions on
disposal.
NOTES ON DISPOSAL (YAMAHA DEALERS
ONLY)
Before disposing the rear shock absorber, be
sure to extract the nitrogen gas from valve 1.
Wear eye protection to prevent eye damage
from escaping gas and/or metal chips.
WARNING
To dispose of a damaged or worn-out rear
shock absorber, take the unit to your
Yamaha dealer for this disposal procedure.
5PA51880
REAR SHOCK ABSORBER

5 - 60
CHAS
EC584000
INSPECTION
Rear shock absorber
1. Inspect:

Damper rod 1
Bends/damage → Replace rear shock
absorber assembly.

Shock absorber 2
Oil leaks → Replace rear shock absorber
assembly.
Gas leaks → Replace rear shock absorber
assembly.

Spring 3
Damage → Replace spring.
Fatigue → Replace spring.
Move spring up and down.

Spring guide 4
Wear/damage → Replace spring guide.
5PA51890
EC585000
ASSEMBLY AND INSTALLATION
Spring (rear shock absorber)
1. Install:

Spring 1

Spring guide 2
5PA51900
2. Tighten:

Adjuster 1
5PA51910
REAR SHOCK ABSORBER

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

6 - 4
–+ELECIGNITION SYSTEM
EC626002
IGNITION COIL INSPECTION
1. Inspect:

Primary coil resistance
Out of specification → Replace.
2. Inspect:

Secondary coil resistance
Out of specification → Replace.
NOTE:

Remove the spark plug cap by turning it
counterclockwise and inspect.

Install the spark plug cap by turning it clock-
wise until it is tight.
SPARK PLUG CAP INSPECTION
1. Inspect:

Spark plug cap
Loose connection → Tighten.
Deteriorated/Damaged → Replace.

Spark plug cap resistance
Out of specification → Replace. 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
Tester (+) lead
→ Spark plug lead
1
Tester (–) lead
→ Orange lead
2
Secondary coil
resistanceTester selector
position
6.3 ~ 9.5 k
Ω at
20 °C (68 °F)k
Ω
× 1
Tester (+) lead
→
Spark plug lead terminal
1
Tester (–) lead
→ Spark plug terminal
2
Spark plug cap
resistanceTester selector
position
4 ~ 6 k
Ω at
20 °C (68 °F)k
Ω
× 1
5PA60060
5PA60070
5PA60070
5PA60070
2
1

6 - 5
–+ELECIGNITION SYSTEM
CDI MAGNETO INSPECTION
1. Inspect:

Pickup coil resistance
Out of specification → Replace.
Tester (+) lead
→ White/Red lead
1
Tester (–) lead
→ White/Blue lead
2
Pickup coil
resistanceTester selector
position
248 ~ 372
Ω at
20 °C (68 °F)Ω
× 100
5PA60080
2. Inspect:

Charging coil 1 resistance
Out of specification → Replace.
3. Inspect:

Charging coil 2 resistance
Out of specification → Replace.
EC628000
CDI UNIT INSPECTION
Check all electrical components. If no fault is
found, replace the CDI unit. Then check the
electrical components again.Tester (+) lead
→ Black/Red lead
1
Tester (–) lead
→ Green/White lead
2
Charging coil 1
resistanceTester selector
position
720 ~ 1,080
Ω
at 20 °C (68 °F)Ω
× 100
Tester (+) lead
→ Green/Blue lead
1
Tester (–) lead
→ Black lead
2
Charging coil 2
resistanceTester selector
position
44 ~ 66
Ω at
20 °C (68 °F)Ω
× 10
5PA60090
5PA60100

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