YAMAHA YZ250F 2008 Owners Manual

7-1
ENGINE
TUNING
ENGINE
CARBURETOR SETTING
• The air/fuel mixture will vary de-pending on atmospheric conditions.
Therefore, it is necessary to take
into consideration the air pressure,
ambient temperature, humidity,
etc., when adjusting the carburetor.
• Perform a test run to check for prop- er engine performance (e.g., throt-
tle response) and spark plug(-s)
discoloration or fouling. Use these
readings to determine the best pos-
sible carburetor setting.
It is recommended to keep a record of
all carburetor settings and external
conditions (e.g., atmospheric condi-
tions, track/surface conditions, lap
times) to make future carburetor set-
ting easier.
• The carburetor is a part of the fuel line. Therefore, be sure to in-
stall it in a wellventilated area,
away from flammable objects
and any sources of fire.
• Never look into the carburetor in- take. Flames may shoot out from
the pipe if the engine backfires
while it is being started. Gasoline
may be discharged from the ac-
celerator pump nozzle when the
carburetor has been removed.
• The carburetor is extremely sen-sitive to foreign matter (dirt,
sand, water, etc.). During instal-
lation, do not allow foreign mat-
ter to get into the carburetor.
• Always handle the carburetor and its components carefully.
Even slight scratches, bends or
damage to carburetor parts may
prevent the carburetor from
functioning correctly. Carefully
perform all servicing with the ap-
propriate tools and without ap-
plying excessive force.
• When the engine is stopped or when riding at no load, do not
open and close the throttle un-
necessarily. Otherwise, too
much fuel may be discharged,
starting may become difficult or
the engine may not run well.
• After installing the carburetor,
check that the throttle operates correctly and opens and closes
smoothly.
ATMOSPHERIC CONDITIONS AND
CARBURETOR SETTINGS
The air density (i.e., concentration of
oxygen in the air) determines the rich-
ness or leanness of the air/fuel mix-
ture.
• Higher temperature expands the air
with its resultant reduced density.
• Higher humidity reduces the amount of oxygen in the air by so
much of the water vapor in the
same air.
• Lower atmospheric pressure (at a high altitude) reduces the density of
the air.
EFFECT OF SETTING PARTS IN
RELATION TO THROTTLE VALVE
OPENING
A. Closed
B. Fully open
1. Pilot screw/pilot jet
2. Throttle valve cutaway
3. Jet needle
4. Main jet CONSTRUCTION OF
CARBURETOR AND SETTING
PARTS
The FLATCR carburetor has a prima-
ry main jet. This type of main jet is
perfect for racing machines since it
supplies an even flow of fuel, even at
full load. Use the main jet and the jet
needle to set the carburetor.
The FLATCR carburetor is manufac-
tured with a pilot screw. The pilot
screw adjustment ranges from fully
closed throttle to 1/4 open throttle.
1. Jet needle
2. Pilot air jet
3. Needle jet
4. Main jet
5. Pilot jet
6. Pilot screw
ADJUSTING THE MAIN JET
The richness of the air-fuel mixture at
full throttle can be set by changing the
main jet "1".
If the air-fuel mixture is too rich or too
lean, the engine power will drop, re-
sulting in poor acceleration.
Effects of changing the main jet
(reference)
A. Idle
B. Fully open
1. #180
2. #175
3. #178
Air
tem p. Hu-
midi- ty Air
pres-
sure
(alti-
tude) Mix-
ture Set-
ting
High High Low
(high) Rich-
er Lean-
er
Low Low High
(low) Lean-
er Rich-
er
Standard main jet #178
7

7-2
ENGINE
ADJUSTING THE PILOT SCREW
The richness of the air-fuel mixture
with the throttle fully closed to 1/4
open can be set by turning the pilot
screw "1". Turning in the pilot screw
will make the mixture lean at low
speeds, and turning it out will enrich
it.
• If the engine idling speed fluctuates, turn the pilot screw only 1/2 of a turn
in either direction.
• To optimize the fuel flow at a small- er throttle opening, each machine's
pilot screw has been individually set
at the factory. Before adjusting the
pilot screw, turn it in fully and count
the number of turns. Record this
number as the factory-set number
of turns out.
Effects of adjusting the pilot screw
(reference)
A. Idle
B. Fully open
1. 2-7/8 turns out
2. 1-7/8 turns out
3. 2-3/8 turns out
ADJUSTING THE PILOT JET
The richness of the air-fuel mixture
with the throttle open 1/4 or less can
be set by adjusting the pilot jet "1".
Effects of adjusting the pilot jet
(reference) A. Idle
B. Fully open
1. #45
2. #40
3. #42
ADJUSTING THE JET NEEDLE
GROOVE POSITION
Adjusting the jet needle "1" position
affects the acceleration when the
throttle is 1/8 to 3/4 open.
1. Too rich at intermediate speeds • Rough engine operation is felt
and the engine will not pick up
speed smoothly.
Step up the jet needle clip by one
groove and move down the nee-
dle to lean out the mixture.
2. Too lean at intermediate speeds
• The engine breathes hard and will not pick up speed quickly.
Step down the jet needle clip by
one groove and move up the nee-
dle to enrich the mixture.
Effects of changing the jet needle
groove position (reference) A. Idle
B. Fully open
1. No.6 groove
2. No.4 groove
3. No.5 groove
ADJUSTING THE JET NEEDLE
The jet needle is adjusted by chang-
ing it.
The jet needle setting parts, having
the same taper angle, are available in
different straight portion diameters
and in different taper starting posi-
tions. a. Diameter of the straight por- tion
b. Reference needle
c. 0.5 leaner
Changing from NFPR-5 to NFLR-5
has the same effect as a lowering of
0.5 clip position. Effects of changing the jet needle
(reference)
(Diameter of the straight portion)
Changing the diameter of the straight
portion adjusts the air-fuel mixture
when the throttle is 1/8 to 1/4 open.
A. Idle
B. Fully open
RELATIONSHIP WITH THROTTLE
OPENING
The flow of the fuel through the car-
buretor main system is controlled by
the main jet and then, it is further reg-
ulated by the area between the main
nozzle and the jet needle.
The fuel flow relates to the diameter
of the straight portion of the jet needle
with the throttle 1/8 to 1/4 open and
relates to the clip position with the
throttle 1/8 to 3/4 open.
Therefore, the fuel flow is balanced at
each stage of throttle opening by the
combination of the jet needle straight
portion diameter and clip position.
ADJUSTING THE LEAK JET
(ADJUSTING THE ACCELERATOR
PUMP)
The leak jet "1" is a setting part that
adjusts the flow of fuel discharged by
the accelerator pump. Since the ac-
celerator pump operates only when
throttle is open, the leak jet is used to
adjust a fuel mixture ratio for quick
throttle opening and is therefore dif-
ferent from other setting parts that ad-
just a fuel mixture for each throttle
opening (each engine speed).
1. When the engine breathes hard in quick throttle opening, select a
leak jet having lower calibrating
No. than standard to enrich the
mixture. #70
→#60
Standard pilot screw
position (example) 2-3/8
Standard pilot jet #42
Standard clip posi- tion No.5
groove
Standard jet needle NFPR

7-3
ENGINE
2. When rough engine operation is felt in quick throttle opening, se-
lect a leak jet having higher cali-
brating No. than standard to lean
out the mixture. #70
→#80 CARBURETOR SETTING PARTS
Standard leak jet #70
Main jet Size Part number Rich #188 4MX-14943-95 #185 4MX-14943-44
#182 4MX-14943-94
#180 4MX-14943-43
(STD) #178 4MX-14943-93 #175 4MX-14943-42
#172 4MX-14943-92
#170 4MX-14943-41
Lean #168 4MX-14943-91
Pilot jet Size Part number Rich #48 4MX-14948-06 #45 4MX-14948-05
(STD) #42 4MX-14948-04 #40 4MX-14948-03
Lean #38 4MX-14948-02
Jet needle Size Part number Rich NFPN 5TA-14916-PN NFPP 5TA-14916-PP
NFPQ 5TA-14916-P1
(STD) NFPR 5TA-14916-PR NFPS 5TA-14916-PSNFPT 5TA-14916-PT
Lean NFPU 5TA-14916-PU Rich NFLN 5TA-14916-LN NFLP 5TA-14916-LP
NFLQ 5TA-14916-L1
NFLR 5TA-14916-LRNFLS 5TA-14916-LSNFLT 5TA-14916-LT
Lean NFLU 5TA-14916-LU
Leak jet Size Part number Rich #40 4JT-1494F-03 #50 4JT-1494F-07
#60 4JT-1494F-11
(STD) #70 4JT-1494F-15 #80 4JT-1494F-19
#90 4JT-1494F-23
Lean #100 4JT-1494F-27

7-4
ENGINE
SPECIFICATIONS OF JET NEEDLE
EXAMPLES OF CARBURETOR SETTING DEPENDING ON SYMPTOMDiameter of straight portion
Rich Lean
NPQRS TU
Rich 1 richer NFPN-6 NFPP-6 NFPQ-6 NFPR-6 NFPS-6 NFPT-6 NFPU-6 0.5 richer NFLN-6 NFLP-6 NFLQ-6 NFLR-6 NFLS-6 NFLT-6 NFLU-6STD NFPN-5 NFPP-5 NFPQ-5 NFPR-5 NFPS-5 NFPT-5 NFPU-5
0.5 leaner NFLN-5 NFLP-5 NFLQ-5 NFLR-5 NFLS-5 NFLT-5 NFLU-5
Lean 1 leaner NFPN-4 NFPP-4 NFPQ-4 NFPR-4 NFPS-4 NFPT-4 NFPU-4
Symptom Setting Checking
At full throttle Hard breathing
Shearing noise
Whitish spark plug
↓
Lean mixture Increase main jet calibration no. (Gradual-
ly)
Discoloration of spark plug
→If tan color, it
is in good condition.
If cannot be corrected: Clogged float valve seat
Clogged fuel hose
Clogged fuel cock
Check that the accelerator pump operates
smoothly.
At full throttle Speed pick-up stops
Slow speed pick-up
Slow response
Sooty spark plug
↓
Rich mixture Decrease main jet calibration no. (Gradual-
ly)
Discoloration of spark plug
→If tan color, it
is in good condition.
If cannot be corrected:
Clogged air filter
Fuel overflow from carburetor
Lean mixture Lower jet needle clip position. (1 groove
down)
The clip position is the jet needle groove on
which the clip is installed.
The positions are numbered from the top.
Check that the accelerator pump operates
smoothly. (except for rich mixture symp-
tom).
Rich mixture
Raise jet needle clip position. (1 groove up)
1/4–3/4 throttle Hard breathing
Lack of speed Lower jet needle clip position. (1 groove
down)
1/4–1/2 throttle Slow speed pick-up
Poor acceleration Raise jet needle clip position. (1 groove up)
Closed to 1/4 throttle Hard breathing
Speed down Use jet needle with a smaller diameter. Slow-speed-circuit passage
Clogged
→Clean.
Overflow from carburetor
Closed to 1/4 throttle Poor acceleration Use jet needle with a larger diameter.
Raise jet needle clip position. (1 groove up)
Poor response in the low to in-
termediate speeds Raise jet needle clip position.
If this has no effect, lower the jet needle clip
position.
Poor response when throttle is
opened quickly Check overall settings.
Use main jet with a lower calibration no.
Raise jet needle clip position. (1 groove up)
If these have no effect, use a main jet with
a higher calibration no. and lower the jet
needle clip position. Check air filter for fouling.
Check that the accelerator pump operates
smoothly.
Jet needleClip
Groove 7 Groove 6
Groove 5
Groove 4
Groove 3
Groove 2
Groove 1
Leaner
(Standard) Richer

7-5
ENGINE
* This should be taken simply for an example. It is necessary to set the carburetor while checking the operating conditions
of the engine.

7-6
CHASSIS
CHASSIS
SELECTION OF THE SECONDARY
REDUCTION RATIO (SPROCKET)
ondary gear reduction ratio>
• It is generally said that the second-ary gear ratio should be reduced for
a longer straight portion of a speed
course and should be increased for
a course with many corners. Actual-
ly, however, as the speed depends
on the ground condition of the day
of the race, be sure to run through
the circuit to set the machine suit-
able for the entire course.
• In actuality, it is very difficult to achieve settings suitable for the en-
tire course and some settings may
be sacrificed. Thus, the settings
should be matched to the portion of
the course that has the greatest ef-
fect on the race result. In such a
case, run through the entire course
while making notes of lap times to
find the best balance; then, deter-
mine the secondary reduction ratio.
• If a course has a long straight por-
tion where a machine can run at
maximum speed, the machine is
generally set such that it can devel-
op its maximum revolutions toward
the end of the straight line, with care
taken to avoid the engine over-rev-
ving.
Riding technique varies from rider to
rider and the performance of a ma-
chine also vary from machine to ma-
chine. Therefore, do not imitate other
rider's settings from the beginning but
choose your own setting according to
the level of your riding technique.
DRIVE AND REAR WHEEL
SPROCKETS SETTING PARTS
TIRE PRESSURE
Tire pressure should be adjust to suit
the road surface condition of the cir-
cuit.
• Under a rainy, muddy, sandy, or slippery condition, the tire pressure
should be lower for a larger area of
contact with the road surface.
• Under a stony or hard road condi- tion, the tire pressure should be
higher to prevent a flat tire.
FRONT FORK SETTING
The front fork setting should be made
depending on the rider's feeling of an
actual run and the circuit conditions. The front fork setting includes the fol-
lowing three factors:
1. Setting of air spring characteris-
tics
• Change the fork oil amount.
2. Setting of spring preload • Change the spring.
3. Setting of damping force • Change the compression damp-ing.
• Change the rebound damping. The spring acts on the load and
the damping force acts on the
cushion travel speed.
CHANGE IN AMOUNT AND
CHARACTERISTICS OF FORK OIL
Damping characteristic near the final
stroke can be changed by changing
the fork oil amount.
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 cause the air spring
characteristics to have a tendency
to be stiffer with the consequent
deteriorated performance and
characteristics. Therefore, adjust
the front fork within the specified
range.
A. Air spring characteristics in relation to oil amount change
B. Load
Secondary reduction ratio =
Number of rear wheel sprocket
teeth/Number of drive sprocket
teeth
Standard secondary
reduction ratio 49/13
(3.769)
Part name Size Part number
Drive
sprocket "1" (STD) 13T 9383B-13218
Rear wheel
sprocket "2" 47T 1C3-25447-00
48T 1C3-25448-00
(STD) 49T 1C3-25449-00 50T 1C3-25450-00
51T 1C3-25451-00
52T 1C3-25452-00
Standard tire pressure: 100 kPa (1.0 kgf/cm
2,
15 psi)
Extent of adjustment: 60–80 kPa (0.6–0.8 kgf/
cm
2, 9.0–12 psi)
Extent of adjustment: 100–120 kPa (1.0–1.2
kgf/cm
2, 15–18 psi)
Standard oil amount:330 cm3 (11.6 Imp oz,
11.2 US oz)
Extent of adjustment: 300–375 cm
3(10.6–13.2
Imp oz, 10.1–12.7 US
oz)

7-7
CHASSIS
C. Stroke
1. Max. oil amount
2. Standard oil amount
3. Min. oil amount
SETTING OF SPRING AFTER
REPLACEMENT
As the front fork setting can be easily
affected by rear suspension, take
care so that the machine front and
rear are balanced (in position, etc.)
when setting the front fork.
1. Use of soft spring • Change the rebound damping.Turn out one or two clicks.
• Change the compression damp-
ing.
Turn in one or two clicks.
Generally a soft spring gives a soft
riding feeling. Rebound damping
tends to become stronger and the
front fork may sink deeply over a se-
ries of gaps.
2. Use of stiff spring• Change the rebound damping.Turn in one or two clicks.
• Change the compression damp-
ing.
Turn out one or two clicks.
Generally a stiff spring gives a stiff
riding feeling. Rebound damping
tends to become weaker, resulting in
lack of a sense of contact with the
road surface or in a vibrating handle-
bar.
FRONT FORK SETTING PARTS
• Front fork spring "1"
The I.D. mark (slits) "a" is proved on the end of the spring.
REAR SUSPENSION SETTING
The rear suspension setting should
be made depending on the rider's
feeling of an actual run and the circuit
conditions.
The rear suspension setting includes
the following two factors:
1. Setting of spring preload
• Change the set length of the spring.
• Change the spring.
2. Setting of damping force • Change the rebound damping.
• Change the compression damp-ing.
CHOOSING SET LENGTH
1. Place a stand or block under the engine to put the rear wheel
above the floor, and measure the
length "a" between the rear wheel
axle center and the rear fender
holding bolt.
2. Remove the stand or block from the engine and with a rider astride
the seat, measure the sunken
length "b" between the rear wheel
axle center and the rear fender
holding bolt. 3. Loosen the locknut "1" and make
adjustment by turning the spring
adjuster "2" to achieve the stan-
dard figure from the subtraction of
the length "b" from the length "a".
• If the machine is new and after it is broken in, the same set length of
the spring may change because of
the initial fatigue, etc. of the spring.
Therefore, be sure to make reeval-
uation.
• If the standard figure cannot be achieved by adjusting the spring
adjuster and changing the spring
set length, replace the spring with
an optional one and make readjust-
ment.
SETTING OF SPRING AFTER
REPLACEMENT
After replacement, be sure to adjust
the spring to the set length [sunken
length 90–100 mm (3.5–3.9 in)] and
set it.
1. Use of soft spring• Set the soft spring for less re-bound damping to compensate
for its less spring load. Run with
the rebound damping adjuster
one or two clicks on the softer
side and readjust it to suit your
preference.
2. Use of stiff spring
• Set the soft spring for more re-bound damping to compensate
for its greater spring load. Run
with the rebound damping adjust-
er one or two clicks on the stiffer
side and readjust it to suit your
preference.
Adjusting the rebound damping will
be followed more or less by a change
in the compression damping. For cor-
rection, turn the low compression
damping adjuster on the softer side.
TY
PE SPRIN
G
RATE SPRING
PART NUM- BER I.D.
MA
RK
(slit
s)
SO FT 0.398 1C3-23141-A1 |
0.408 1C3-23141-B1 ||
0.418 1C3-23141-C1 |||
0.428 1C3-23141-D1 ||||
0.438 1C3-23141-E1 |||||
ST D 0.449 5XC-23141-
N0—
STI FF 0.459 1C3-23141-
G1|-||
0.469 1C3-23141-H1 |-|||
0.479 1C3-23141-J1 |-||||
Standard figure: 90–100 mm (3.5–3.9 in)

7-8
CHASSIS
When using a rear shock absorber
other than currently installed, use
the one whose overall length "a"
does not exceed the standard as it
may result in faulty performance.
Never use one whose overall
length is greater than standard.
REAR SHOCK ABSORBER
SETTING PARTS
• Rear shock spring "1"
[Equal-pitch titanium spring]
[Equal-pitch steel spring][Unequal-pitch steel spring]
Install the spring seat "2" to the ti-
tanium spring.
• The unequal-pitch spring is softer in
initial characteristic than the equal-
pitch spring and is difficult to bottom
out under full compression.
• The I.D. mark "a" is marked at the end of the spring.
• Spring specification varies accord-
ing to the color and quantity of I.D.
marks.
• Extent of adjustment (spring length) [Titanium spring]
[Steel spring]
Length "a" of standard
shock:
490 mm (19.29 in)
T
Y
P
E SPRI
NG
RAT
E SPRING
PART
NUM-
BER -
22212- I.D.
MARK SPR
ING
FRE E
LEN
GTH
(ap-
prox
.)
S
O F
T 4.5 1C3-00 Green 265
4.7 1C3-10 Red 265
4.9 1C3-20 Black 265
5.1 1C3-30 Blue 265
S T
D 5.3
1C3-40
(1C3-A0) Yellow 275
S
TI
F
F 5.5 1C3-50 Pink 275
5.7 1C3-60 White 275
T
Y
P
E SPRI
NG
RAT
E SPRING
PART NUM-
BER -
22212- I.D.
MARK/
Q'TY SPR
ING
FRE E
LEN
GTH
4.3 5UN-00 Brown/1 260
T
Y
P
E SPRI
NG
RAT
E
(ap-
prox. ) SPRING
PART
NUM-
BER -
22212- I.D.
MARK/ Q'TY SPR
ING
FRE E
LEN
GTH
S
O
F
T 4.5 5UN-A0 Green/2 275
4.75UN-B0Red/2275
4.9 5UN-C0 Black/2 275
5.1 5UN-D0 Blue/2 275
5.3 5UN-E0
Yellow/
2 275
5.5 5UN-F0 Pink/2 275
S
TI F
F 5.7
5UN-
22212- G0 White/2 275
SPRING
FREE
LENGTH EXTENT OF AD-
JUSTMENT "b"
Approx. 265 mm
(10.43 in) One I.D. mark
245.5–263.5 mm (9.67–10.37 in)
Two I.D. marks
251.5–269.5 mm (9.90–10.61 in)
Three I.D. marks 243.0–261.0 mm (9.57–10.28 in)
Approx. 275 mm
(10.83 in) One I.D. mark
255.5–273.5 mm (10.06–10.77 in)
Two I.D. marks
261.5–279.5 mm (10.30–11.00 in)
Three I.D. marks 253.0–271.0 mm (9.96–10.67 in)
SPRING FREE
LENGTH EXTENT OF AD-
JUSTMENT "b"
260 mm
(10.24 in) 240.5–258.5 mm
(9.47–10.18 in)
275 mm
(10.83 in) 255.5–273.5 mm
(10.06–10.77 in)

7-9
CHASSIS
SUSPENSION SETTING (FRONT FORK)
• 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 90–100 mm (3.5–3.9 in).
Symptom Section
Check Adjust
Jump Large
gap Medi-
um
gap Small
gap
Stiff over entire
range
○○○
Compression damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Oil amount Decrease oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).
Spring Replace with soft spring.
Unsmooth move-
ment over entire
range
○○○○
Outer tube Check for any bends, dents, and other noticeable
scars, etc. If any, replace affected parts.
Inner tube
Slide metal Replace with a new one for extended use.
Piston metal Replace with a new one for extended use.
Under bracket tighten-
ing torque Retighten to specified torque.
Poor initial move-
ment
○
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Oil seal Apply grease in oil seal wall.
Soft over entire
range, bottoming
out
○○
Compression damping Turn adjuster clockwise (about 2 clicks) to in- crease damping.
Oil amount Increase oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).
Spring Replace with stiff spring.
Stiff toward stroke
end
○Oil amount Decrease oil amount by about 5 cm3 (0.2 Imp
oz,0.2 US oz).
Soft toward stroke
end, bottoming out
○Oil amount Increase oil amount by about 5 cm3 (0.2 Imp
oz,0.2 US oz).
Stiff initial move-
ment
○○○○Compression damping Turn adjuster counterclockwise (about 2 clicks) to
decrease damping.
Low front, tending to
lower front posture
○○
Compression damping Turn adjuster clockwise (about 2 clicks) to in- crease damping.
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Balance with rear end Set sunken length for 95–100 mm (3.7–3.9 in) when one passenger is astride seat (lower rear
posture).
Oil amount Increase oil amount by about 5 cm
3 (0.2 Imp oz,
0.2 US oz).
"Obtrusive" front,
tending to upper
front posture
○○
Compression damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Balance with rear end Set sunken length for 90–95 mm (3.5–3.7 in) when one passenger is astride seat (upper rear
posture).
Spring Replace with soft spring.
Oil amount Decrease oil amount by about 5–10 cm
3 (0.2–0.4
Imp oz, 0.2–0.3 US oz).

7-10
CHASSIS
SUSPENSION SETTING (REAR SHOCK ABSORBER)
• 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.
• Adjust the rebound damping in 2-click increments or decrements.
• Adjust the low compression damping in 1-click increments or decrements.
• Adjust the high compression damping in 1/6 turn increments or decrements.
Symptom Section
Check Adjust
Jump Large
gap Medi-
um
gap Small
gap
Stiff, tending to sink
○○
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in) when one passenger is astride seat.
Spongy and unsta-
ble
○○
Rebound damping Turn adjuster clockwise (about 2 clicks) to in- crease damping.
Low compression
damping Turn adjuster clockwise (about 1 click) to increase
damping.
Spring Replace with stiff spring.
Heavy and dragging
○○
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Spring Replace with soft spring.
Poor road gripping
○
Rebound damping Turn adjuster counterclockwise (about 2 clicks) to decrease damping.
Low compression
damping Turn adjuster clockwise (about 1 clicks) to in-
crease damping.
High compression
damping Turn adjuster clockwise (about 1/6 turn) to in-
crease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in) when one passenger is astride seat.
Spring Replace with soft spring.
Bottoming out
○○
High compression
damping Turn adjuster clockwise (about 1/6 turn) to in-
crease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in) when one passenger is astride seat.
Spring Replace with stiff spring.
Bouncing
○○
Rebound damping Turn adjuster clockwise (about 2 clicks) to in- crease damping.
Spring Replace with soft spring.
Stiff travel
○○
High compression
damping Turn adjuster counterclockwise (about 1/6 turn) to
decrease damping.
Spring set length Set sunken length for 90–100 mm (3.5–3.9 in) when one passenger is astride seat.
Spring Replace with soft spring.