2005 YAMAHA YZ250LC oil pressure

5-33
CHASFRONT FORK
4. After filling, pump the damper assembly 1
slowly up and down (about 200 mm (7.9 in)
stroke) several times to bleed the damper
assembly of air.
NOTE:
Be careful not to excessive full stroke. A
stroke of 200 mm (7.9 in) or more will cause
air to enter. In this case, repeat the steps 2 to
4.
5. Inspect:
9Oil amount
While keeping the damper assembly fully
stretched, check that the oil is above the
step aon the damper assembly.
Below the stepReplenish fork oil above
the step.
6. Tighten:
9Locknut 1
NOTE:
Fully finger tighten the locknut onto the
damper assembly.
7. Loosen:
9Compression damping adjuster 1
NOTE:
9Loosen the compression damping adjuster fin-
ger tight.
9Record the set position of the adjuster (the
amount of turning out the fully turned in posi-
tion).
8. Install:
9Base valve 1
To damper assembly 2.
NOTE:
First bring the damper rod pressure to a maxi-
mum. Then install the base valve while releas-
ing the damper rod pressure.
1P8-9-30-5B 20/5/04 2:11 PM Page 16

5-62
CHASREAR SHOCK ABSORBER
EC586000
HANDLING NOTE
w
This shock absorber is provided with a
separate type tank filled with high-pressure
nitrogen gas. To prevent the danger of ex-
plosion, read and understand the following
information before handling the shock ab-
sorber.
The manufacturer can not be held respon-
sible for property damage or personal in-
jury that may result from improper han-
dling.
1. Never tamper or attempt to disassemble
the cylinder or the tank.
2. Never throw the shock absorber into an
open flame or other high heat. The shock
absorber may explode as a result of ni-
trogen 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 sur-
face of the piston rod with the cylinder;
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 shock absorber, fol-
low the instructions on disposal.
EC587000
NOTES ON DISPOSAL (YAMAHA DEAL-
ERS ONLY)
Before disposing the 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.
w
To dispose of a damaged or worn-out
shock absorber, take the unit to your
Yamaha dealer for this disposal procedure.
1P8-9-30-5D 11/5/04 11:07 AM Page 20

7-1
SETTINGTUN
EC700000
TUNINGEC710000
ENGINEEC711001
Carburetor setting
9The 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. Accord-
ingly, 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.
9The richness of the air-fuel mixture required for
the engine will vary with atmospheric conditions
of the day and therefore, the settings of the car-
buretor must be properly suited to the atmos-
pheric conditions (air pressure, humidity and
temperature).
9Finally, the rider himself must make a test-run
and check his machine for conditions (pick-up
of engine speed, road surface conditions) 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 condition,
lap-time, etc. so that the memorandum can be
used as a reference useful for future.
EC712000
Atmospheric conditions and carburetor
setting
The reason for the above tendency is that the
richness or leanness of a fuel mixture depends
on the density of the air (i.e. the concentration of
oxygen in it).
Air
Air temp. Humidity pressure Mixture Setting
(altitude)
High HighLow
Richer Leaner
(high)
Low LowHigh
Leaner Richer
(low)
1P8-9-30-7 20/5/04 2:10 PM Page 2

7-2
SETTINGTUN
That is:
9Higher temperature expands the air with its
resultant reduced density.
9Higher humidity reduces the amount of oxygen
in the air by so much of the water vapor in the
same air.
9Lower atmospheric pressure (at a high altitude)
reduces the density of the air.
EC713001
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 discoloration
of spark plug(s).
åNormal
∫Over burned (too lean)
çOil fouled (too rich)
Discoloration Condition of spark plug
NormalInsulator is dry and
burnt brown.
Over burned
Insulator is whitish.
(too lean)
Oil fouled Insulator is sooty and
(too rich) wet.
A
B
C
1P8-9-30-7 20/5/04 2:10 PM Page 4

7-15
SETTINGTUN
A
EC722011
Front fork setting
The front fork setting should be made depending
on the rider’s feeling of an actual run and the cir-
cuit conditions.
The front fork setting includes the following three
factors:
1. Setting of air spring characteristics
9Change the fork oil amount.
2. Setting of spring preload
9Change the spring.
9Install the adjustment washer.
3. Setting of damping force
9Change the compression damping.
9Change the rebound damping.
The spring acts on the load and the damp-
ing force acts on the cushion travel speed.
EC723001
Change in amount and characteristics of fork
oil
Damping characteristic near the final stroke can
be changed by changing the fork oil amount.
cC
Adjust the oil amount in 5 cm3(0.2 Imp oz,
0.2 US oz) increments or decrements. Too
small oil amount causes the front fork to
produce a noise at full rebound or the rider
to feel some pressure on his hands or
body. Alternatively, too large oil amount
will develop unexpectedly early oil lock
with the consequent shorter front fork trav-
el and deteriorated performance and char-
acteristics. Therefore, adjust the front fork
within the specified range.
åAir spring characteristics in relation to oil amount
change
∫Load
çStroke
1Max. oil amount
2Standard oil amount
3Min. oil amount
Standard oil amount:
245 cm
3(8.62 Imp oz, 8.28 US oz)
Extent of adjustment:
200~300 cm
3(7.04~10.6 Imp oz,
6.76~10.1 US oz)
1P8-9-30-7 20/5/04 2:10 PM Page 34