2003 YAMAHA YZ85 oil

7 - 9
TUNSETTING
Change of the heat range of spark plugs
Judging from the discoloration of spark plugs,
if they are found improper, it can be corrected
by the following two methods; changing carbu-
retor settings and changing the heat range of
spark plug.

In principle, it is advisable to first use spark
plugs of standard heat range, and judging
from the discoloration of spark plugs, adjust
carburetor settings.

If the calibration No. of the main jet must be
changed by ±30, it is advisable to change the
heat range of spark plugs and newly select
the proper main jet.
NOTE:

When checking the discoloration of spark
plugs, be sure to stop the engine immedi-
ately after a run and check.

Avoid racing.

When changing the heat range of spark
plugs, never attempt to change it more than
±1 rank.

When using a spark plug other than stan-
dard, check its heat range against the stan-
dard and check that it is a resistance type.

Note that even if the discoloration seems
proper, it may slightly vary with the spark
plug maker and oil in use.Standard spark plugBR10EG/NGK
(resistance type)
5PA70110

7 - 12
TUN
Front fork setting
The front fork setting should be made depend-
ing on the rider’s feeling of an actual run and
the circuit conditions.
The front fork setting includes the following
three factors:
1. Setting of air spring characteristics

Change the fork oil level.
2. Setting of spring preload

Change the spring.
3. Setting of damping force

Change the compression damping.

Change the rebound damping.
The spring acts on the load and the damp-
ing force acts on the cushion travel speed.
EC723001
Change in level and characteristics of fork
oil
Damping characteristic near the final stroke
can be changed by changing the fork oil
amount.
CAUTION:
Adjust the oil level in 5 mm (0.2 in) incre-
ments or decrements. Too low oil level
causes the front fork to produce a noise at
full rebound or the rider to feel some pres-
sure on his hands or body. Alternatively,
too high oil level will develop unexpectedly
early oil lock with the consequent shorter
front fork travel and deteriorated perfor-
mance an characteristics. Therefore, adjust
the front fork within the specified range.
ÈAir spring characteristics in relation to oil level
change
ÉLoad
ÊStroke
1Max. oil level
2Standard oil level
3Min. oil level
Standard oil level:
90 mm (3.54 in)
Extent of adjustment:
80 ~ 120 mm (3.15 ~ 4.72 in)
From top of outer tube with
inner tube and damper rod fully
compressed without spring.
5PA70130
SETTING

7 - 18
TUNSETTING
Suspension setting

Front fork
NOTE:

If any of the following symptoms is experienced with the standard position as the base, make
resetting by reference to the adjustment procedure given in the same chart.

Before any change, set the rear shock absorber sunken length to the standard figure 75 ~ 85 mm
(3.0 ~ 3.3 in).
SymptomSection
Check Adjust
JumpLarge
gapMedium
gapSmall
gap
Stiff over entire range
{{{Compression damping
Oil level (oil amount)
SpringTurn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Decrease oil level by about 5 ~ 10 mm (0.2 ~ 0.4 in).
Replace with soft spring.
Unsmooth movement
over entire range{{{{Outer tube
Inner tube
Under bracket tightening
torqueCheck for any bends, dents, and other noticeable
scars, etc. If any, replace affected parts.
Retighten to specified torque.
Poor initial
movement{Rebound damping
Oil sealTurn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Apply grease in oil seal wall.
Soft over entire range,
bottoming out{{Compression damping
Oil level (oil amount)
SpringTurn adjuster clockwise (about 2 clicks) to increase
damping.
Increase oil level by about 5 ~ 10 mm (0.2 ~ 0.4 in).
Replace with stiff spring.
Stiff toward stroke end{Oil level (oil amount) Decrease oil level by about 5 mm (0.2 in).
Soft toward stroke end,
bottoming out{Oil level (oil amount) Increase oil level by about 5 mm (0.2 in).
Stiff initial movement{{{{Compression dampingTurn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Low front, tending to
lower front posture{{Compression damping
Rebound damping
Balance with rear end
Oil level (oil amount)Turn adjuster clockwise (about 2 clicks) to increase
damping.
Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Set sunken length for 80 ~ 85 mm (3.1 ~ 3.3 in) when
one passenger is astride seat (lower rear posture).
Increase oil level by about 5 mm (0.2 in).
“Obtrusive” front, tend-
ing to upper front pos-
ture{{Compression damping
Balance with rear end
Spring
Oil level (oil amount)Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Set sunken length for 75 ~ 80 mm (3.0 ~ 3.1 in) when
one passenger is astride seat (upper rear posture).
Replace with soft spring.
Decrease oil level by about 5 ~ 10 mm (0.2 ~ 0.4 in).