2003 YAMAHA YZ85 low oil pressure

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.
GENERAL INSPECTION AND MAINTENANCE
Item Routine Page
CoolantCheck that coolant is filled up to the radiator cap.
Check the cooling system for leakage.P.3-5 ~ 9
FuelCheck that a fresh mixture of oil and gasoline is filled in the fuel
tank. Check the fuel line for leakage.P.1-12
Transmission oilCheck that the oil level is correct. Check the crankcase for leak-
age.P.3-12 ~ 13
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
Brakes Check the play of front brake and effect of front and rear brake. P.3-16 ~ 21
Drive chainCheck drive chain slack and alignment. Check that the drive
chain is lubricated properly.P.3-22 ~ 24
WheelsCheck for excessive wear and tire pressure. Check for loose
spokes and have no excessive play.P.3-31 ~ 32
SteeringCheck that the handlebar can be turned smoothly and have no
excessive play.P.3-32 ~ 34
Front forks and rear shock
absorberCheck that they operate smoothly and there is no oil leakage. P.3-24 ~ 30
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.—
Exhaust pipe and silencerCheck that the exhaust pipe is tightly mounted and has no
cracks.P.4-2
Rear wheel sprocket Check that the rear wheel sprocket tightening bolt is not loose. P.3-22
Lubrication Check for smooth operation. Lubricate if necessary. P.3-35
Bolts and nuts Check the chassis and engine for loose bolts and nuts. P.1-16
Lead connectorsCheck that the CDI magneto, CDI unit, and ignition coil are con-
nected tightly.P.1-6
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 ~ 19

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

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