Honda Crf 250 M Manual

							Rear Suspension Adjustments
Adjustments for Competition107 Pin spanners should be used for turning the lock
nut and adjusting nut.  See page 147 for optional
pin spanners.
Spring pre-load length (Standard spring)
Standard:10.29 in (261.3 mm)
Min. :9.88 in (251 mm)
Spring pre-load length (Optional spring)
Min. (Softer, 5.1 kgf/mm): 9.92 in (252 mm)
Min. (Stiffer, 5.5 kgf/mm): 9.80 in (249 mm)
Min. (Stiffer, 5.7 kgf/mm): 9.88 in (251 mm)
The rear suspension can be adjusted for the
rider’s weight and riding conditions by changing
the spring pre-load and the rebound and
compression damping.
The rear shock absorber assembly includes a
damper unit that contains high pressure nitrogen
gas.  Do not attempt to disassemble, service, or
dispose of the damper; see your Honda dealer.
The instructions found in this owner’s manual are
limited to adjustments of the shock assembly
only.
Puncture or exposure to flame may also result in
an explosion, causing serious injury.
Service or disposal should only be done by your
authorized Honda dealer or a qualified mechanic,
equipped with the proper tools, safety equipment
and the official Honda Service Manual.
If your CRF is new, put enough part-throttle
break-in time (about one hour) on it to ensure
that the suspension has worked in.
Rear Suspension Spring Pre-Load
Pre-load should be adjusted when the engine is
cold because it is necessary to remove the
muffler (page 86).
An optional pin spanner is available for turning
the lock nut and adjusting nut to adjust spring
pre-load.
1. Place a workstand under the engine to raise
the rear wheel off the ground.
2. Loosen the connecting tube clamp screw and
remove the rear subframe’s three mounting
bolts, then remove the subframe.  See page
32.3. Check that the spring preload is adjusted to
the standard length.  Adjust as necessary by
loosening the lock nut (1) and turning the
adjusting nut (2).
Each complete turn of the adjuster nut
changes the spring length by 1/16 in (1.5
mm).
(1) lock nut (3) pin spanners
(2) adjusting nut (4) spring length
To increase spring pre-load:
Loosen the lock nut with the optional pin spanner
(3) and turn the adjusting nut to shorten the
spring length (4).  Do not shorten to less than:
8.5 in (215 mm)
T
o decrease spring pre-load:
Loosen the lock nut with the optional pin spanner
(3) and turn the adjusting nut to increase the
spring length (4).  Do not increase to more than:
10.4 in (264 mm)
Each turn of the adjuster changes spring length
and spring pre-load.  One turn equals: spring
length/spring pre-load:
0.06 in (1.5 mm) / 17.5 lbs (7.95 kg)
(1)
(4)
(2)
(3) 
						

							Rear Suspension Adjustments
108Adjustments for Competition(3) rebound damping adjuster
To adjust to the standard position:
1. Turn the adjuster clockwise until it will no
longer turn (lightly seat). This is the full hard
position.
2. Turn the adjuster counterclockwise 9 clicks
with the punch marks on the adjuster and the
shock absorber aligned.
Rear Suspension Damping
Compression Damping
Compression damping may be adjusted in two
stages with separate adjusters.
The high speed damping adjuster (1) is effective
when damping adjustment is desired for high
speed operation.  The low speed damping
adjuster (2) should be used when damping
adjustment is desired at relatively low speeds.
•Both the high and low speed compression
damping can be increased by turning the
appropriate adjuster clockwise.
•Adjust the high speed compression adjuster in
1/12 turn increments. 
(1) high speed damping adjuster
(2) low speed damping adjuster
High Speed Damping: 
The high speed damping can be adjusted by
turning the hexagonal portion of the compression
adjuster.
To adjust to the standard position:
1. Turn the adjuster clockwise until it will no
longer turn (lightly seats). This is the full hard
setting.
2. Turn the adjuster counterclockwise 1-3/4—
2-1/4 turns and the punch marks are aligned.
Low Speed Damping:
The low speed damping can be adjusted by
turning the center screw of the compression
adjuster.
The low speed compression adjuster has 13
positions or more.
Turning the adjuster one full turn clockwise
advances the adjuster four positions.
To adjust to the standard position:
1. Turn the adjuster clockwise until it will no
longer turn (lightly seat). This is the full hard
setting.
2. Turn the adjuster counterclockwise 7 clicks
and the punch marks are aligned.
Rebound Damping
The rebound damping adjuster (3) is located at
the lower end of the shock absorber.
It has 17 positions or more.  Turning the adjuster
one full turn advances the adjuster 9 positions.
•Rebound damping can be increased by turning
the adjuster clockwise.
(2)
(1)
1(3) 
						

							Rear Suspension Adjustments
Adjustments for Competition109 4. Calculate the race sagdimension.
To do this, subtract the loaded with rider
dimension (step 3) from the unloaded
dimension (step 2).
Standard Race Sag: 3.9 in (100 mm)
Adjust spring pre-load as necessary to obtain
the desired handling results.
Decreasing the race sag dimension (example:
3.5 in, 90 mm) improves turning ability for
tight terrain at the cost of slightly reduced
straight line stability.
Increasing the race sag dimension (example:
4.3 in, 110 mm) may improve stability on
faster terrain with less turns, but will reduce
turning performance slightly and may upset
the balance between the front and rear
suspension, producing a harsher ride.  This
will happen if the adjustment shifts the
effective wheel travel toward the more
progressive end of its range.
5. Measure the loaded without riderdimension.
Do this with your motorcycle set at the
standard race sag.
Rear Suspension Race Sag
Setting the proper race sag (ride height) is very
important for competition use.
Race sag refers to the amount of rear wheel
travel used by your CRF at rest, ready to ride,
with you on the seat.  As a general rule of thumb,
the race sag dimension should be about one-third
of the maximum travel.
On your CRF, ride height is changed by adjusting
the rear suspension spring pre-load.
Spring Pre-load & Race Sag 
Adjustment
The following adjustment procedure establishes
the correct starting point for any suspension
tuning — the proper rear spring pre-load
adjustment for your specific needs.
Your CRF should be at normal racing weight,
including fuel and transmission oil.  You should
be wearing all your normal protective apparel.
You will need two helpers.
To calculate the proper adjustment, it is necessary
to measure between two fixed points — from the
top of the most rearward point of the subframe
down to the machined edge at the rear of the
wingarm, as illustrated — for three different
situations:
unloaded: motorcycle on optional workstand with
rear suspension fully extended, no rider.
loaded with rider: motorcycle on ground, with
rider.
loaded without rider: motorcycle on ground,
without rider
1. Support your motorcycle on a workstand with
the rear wheel off the ground.
2. Measure the unloadeddimension.3. Measure the loaded with riderdimension.
Remove the workstand.  With two helpers
available, – sit as far forward as possible on
your CRF’s seat, wearing your riding apparel.
Ask one helper to steady your CRF perfectly
upright so you can put both feet on the pegs.
Bounce your weight on the seat a couple of
times to help the suspension overcome any
situation and settle to a good reference point.
Ask the other helper to measure the loaded
with riderdimension.
Example: 
Unloaded= 23.6 in (600 mm) 
– Loaded= 19.7 in (500 mm)
Race Sag= 3.9 in (100 mm) 
UNLOADED MEASUREMENT
(on workstand, without rider)
EXAMPLE: 23.6 in (600 mm)
LOADED MEASUREMENT
(on ground, with rider)
EXAMPLE: 19.7 in (500 mm)
LOADED MEASUREMENT
(on ground without rider)
EXAMPLE: 21.6 in (550 mm)
Example:
Unloaded= 23.6 in (600 mm) 
– Loaded= 21.6 in (550 mm)
Sag= 2.0 in (50 mm)
(Without Rider) 
(cont’d) 
						

							Rear Suspension Adjustments
110Adjustments for Competition
Because of the great absorption quality of the
shock bumper rubber, it may be difficult for you
to notice when your CRF’s suspension is
bottoming.  Some riders may think the damping
or perhaps the leverage ratio is too harsh.  In
reality, the problem is most likely insufficient
spring pre-load or a spring that is too soft.  Either
situation prevents utilizing the full travel.
Keep in mind that a properly adjusted suspension
system may bottom slightly every few minutes at
full speed.  Adjusting the suspension to avoid this
occasional bottoming may cost more in overall
suspension performance than it is worth.
A spring that is too firm for your weight will not
allow the rear tire to hook up under acceleration
and will pass more bumps on to you. 6. Calculate the free sagdimension.
To do this, subtract the loaded without rider
dimension (step 5) from the unloaded
dimension (step 2).
Free sag indicates the distance your rear
suspension should sag from the weight of the
sprung portion of your CRF.
With the spring pre-load set to obtain the
proper race sag, the rear suspension should
sag: 0.39 to 0.98 in (10 to 25 mm)
If the rear of your CRF sags more than 0.98
in (25 mm) from its own weight, the spring is
too stiff for your weight. It is not compressed
enough, even though you have the proper race
sag adjustment.  As a result, the rear
suspension will not extend as far as it should.
Spring Rates
If you are lighter or heavier than the average
rider and cannot set the proper ride height
without altering the correct spring pre-load,
consider an aftermarket shock absorber spring.
A spring that is too soft for your weight forces
you to add excessive spring pre-load to get the
right race sag and, as a result, the rear end of the
motorcycle is raised.  This can cause the rear
wheel to unload too much in the air and top out
as travel rebounds.  The rear end may top out
from light braking, or kick sideways over lips
and square-edged terrain.  It may even top-out
when you dismount your CRF. 
						

							Suspension Adjustments for Track Conditions
Adjustments for Competition111 Soft Surface
On soft ground, sand, and especially mud,
consider increasing compression damping front
and rear.
Sand often requires a bit more rebound damping
to minimize rear end kick.  Although sand bumps
are usually larger, there’s more distance between
them, giving the shock more time to recover.
You may want a little bit stiffer front suspension
for sand tracks to help keep the front end up and
improve straight-line stability.
In a muddy event, stiffer aftermarket springs
front and rear may help, especially if you are
heavier than the average rider.  Your CRF may be
undersprung because of the added weight of the
clinging mud.  This additional weight may
compress the suspension too much and affect
traction.
Hard Surface
For a fast, hard track with no large jumps, you
can probably run the same spring as normal, but
run softer damping both ways-compression and
rebound.  If you run softer rebound damping, the
wheel will follow the rough ground and small
bumps much better, and you will hook up better.
With a lot of rebound damping, the wheel returns
very slowly and doesn’t contact the ground
quickly enough after each bump.  The result is a
loss of traction and slower lap times. 
						

							Suspension Adjustment  Guidelines
112Adjustments for Competition
Follow the procedures described below to accurately adjust your CRF, using the methods described on pages 94 - 108.  Remember to make all adjustments in
one-click increments.  Test ride after each adjustment.
Front Suspension Adjustment
Adjustments for Type of Track
Adjustments for Too Soft/Stiff Damping
Hard-surfaced track
Sand track
Mud track
Begin with the standard setting.  If the suspension is too stiff/soft, adjust according to the chart below.
Adjust to a stiffer position.
Example:– Turn the compression damping adjuster to a stiffer position.
– Install the optional stiff spring.  (Adjust compression damping to a softer position and rebound damping to a harder position at
this time.)
Adjust to a stiffer position because mud build-up increases your CRF’s weight.
Example:– Turn the compression damping adjuster to a stiffer setting.
– Install the optional stiff spring.
Soft 
suspension
Symptom
Initial travel too soft:
•Steering is too quick.
•Front end darts while cornering or riding in a straight line.
Middle travel too soft:
•Front end dives when cornering.
Final travel too soft:
•Bottoms on landings.
•Bottoms on large bumps, especially downhill bumps.
Entire travel too soft:
•Front end shakes.
•Fork bottoms over any type of terrain.
Action
– Test stiffer compression damping adjustments in one-click increments.
– Test stiffer rebound damping in one-click increments.
If suspension isn’t stiff in initial travel:
– Test stiffer compression damping adjustments in one-click increments.
If initial travel becomes stiff because of the above adjustment:
– Reduce the rebound damping in one-click increments.
– Test softer compression damping adjustments in one-click increments.
If that doesn’t solve the problem, install the optional stiff spring.
If initial and middle travel aren’t stiff:
– Test stiffer compression damping adjustments in one-click increments.
If initial and middle travel are stiff:
– Install the optional stiff spring.
If initial travel is stiff after installing the optional stiff spring:
– Test soft compression damping adjustments in one-click increments.
If initial travel is still soft after installing the optional stiff spring:
– Test stiffer compression damping adjustments in one-click increments.
If final travel is still soft after installing the optional stiff spring:
– Increase the fork oil level in increments of 0.2 oz (5 cc).
– Install the optional stiff spring.
– Test stiffer compression damping adjustments in one-click increments.
– Increase rebound damping in one-click increments. 
						

							Suspension Adjustment  Guidelines
Adjustments for Competition113
Stiff
suspension
Symptom
Initial travel too stiff:
•
Stiff on small bumps while riding at full throttle in a straight line.•Stiff on small cornering bumps.
•Front end wanders while riding at full throttle in a straight line.
Middle travel too stiff:
•Stiff on bumps when cornering.
•Front end wanders when cornering.
•Stiff suspension on bumps, especially downhill bumps.
•While braking, front end dives during initial travel, then feels stiff.
Final travel too stiff:
•Doesn’t bottom on landings, but feels stiff.
•Stiff on large bumps, especially downhill bumps.
•Stiff on large bumps when cornering.
Entire travel too stiff:
•Stiff suspension on any type of terrain.
Action
– Test softer compression damping adjustments in one-click increments.
– Reduce the rebound damping adjustments in one-click increments.
– Check for dirt in the dust seals.  Check the fork oil for any contamination.
If the front end dives while cornering, reduce the rebound damping in one click
increments.  If that doesn’t solve the problem, install the optional stiff spring.
If the stiff spring makes the suspension too stiff over the full range of travel:
test softer compression damping adjustments in one-click increments until the
desire compression damping for initial travel is obtained.
If initial travel isn’t stiff:
– Test stiffer compression damping adjustments in one-click increments. (This
should produce smooth fork action from initial to middle travel.)
If initial and middle travel is stiff:
– Test softer compression damping adjustments in one-click increments.
– Reduce the rebound damping in one-click increments.
If initial and middle travel aren’t stiff:
– Test stiffer compression damping adjustments in one-click increments. (This
should produce smooth fork action from initial to middle travel.)
If final travel is still stiff after the above adjustment, or
If initial and middle travel becomes stiff:
– Install the optional stiff spring.
– Test softer compression damping adjustments in one-click increments.
If the entire travel feels stiff after the above adjustment:
– Test softer compression damping adjustments in one-click increments until the
desired initial travel compression damping is obtained.
– Lower the oil level by 0.2 oz (5 cc).
– Test softer compression damping adjustments in one-click increments.
– Reduce the rebound damping in one-click increments.
– Lower the oil level by 0.2 oz (5 cc). 
						

							Suspension Adjustment  Guidelines
114Adjustments for Competition
Rear Suspension Adjustment
Adjustments for Type of Track
Symptoms and Adjustment
•Always begin with the standard settings.
•Turn the low speed compression and rebound adjusters in one-click increments, and the high speed compression adjuster in 1/6 turn increments at a time.  Adjusting two or
more clicks or turns at a time may cause you to pass over the best adjustment.  Test ride after each adjustment.
•If, after setting, the suspension feels unusual, find the corresponding symptom in the table and test stiffer or softer compression and/or rebound damping adjustments until
the correct settings are obtained as described.
Hard-surfaced track
Sand track
Mud track
Begin with the standard settings.  If the suspension is too stiff/soft, adjust according to the chart below.
Lower the rear end (to improve front wheel stability) by increasing Race Sag (reduce spring preload).
Example:– Turn the compression damping adjuster and, especially, rebound damping adjuster to a stiffer setting.
– Increase standard Race Sag (+0.2 to 0.4 in/5 to 10 mm).
Adjust to a stiffer position because mud build-up increases your CRF’s weight.
Example:– Adjust the compression and rebound damping adjusters to stiffer settings.
– Install the optional stiff spring.
– Reduce standard Race Sag (–0.2 to 0.4 in/5 to 10 mm).
Stiff suspension
Soft suspension
Suspension bottoms
Symptom
Suspension feels stiff on small
bumps
Suspension feels stiff on large
bumps
Entire travel too stiff
Entire travel too soft
Rear end sways
Suspension bottoms at landing
after jumping
Suspension bottoms after landing
Suspension bottoms after end of
continuous bumps
Action
1. Test softer low speed compression adjustment.
2. If it still feels stiff, further test softer low and high speed compression adjustments simultaneously.
1. Test softer high speed compression adjustment.
2. If it still feels stiff, further test softer low and high speed compression adjustments simultaneously.
1. Test softer high and low speed compression adjustments and rebound adjustment simultaneously.
2. If it still feels stiff, replace the spring with a softer spring (optional) and begin with the standard settings to
softer settings.
1. Test stiffer high and low speed compression adjustments simultaneously.
2. If it still feels soft, replace the spring with a harder spring (optional) and begin with the standard settings to
stiffer setting.
1. Test stiffer high and low speed compression adjustments and rebound adjustment to stiffer settings
simultaneously.
1. Test stiffer high speed compression adjustment.
2. If it still bottoms, test stiffer high and low speed compression adjustments, and replace the spring with a
harder spring (optional) if necessary.
1. Test stiffer low speed compression adjustment.
2. If it still bottoms, test stiffer high and low speed compression adjustments, and replace the spring with a
harder spring (optional) if necessary.
1. Test softer rebound dumping adjustment.
2. If it still bottoms, test stiffer high and low speed compression adjustments and softer rebound damping
adjustment, and replace the spring with a harder spring (optional) if necessary. 
						

							Carburetor Adjustments & Tuning Tips
Adjustments for Competition115 The carburetor on your CRF should perform
suitably with the standard recommended settings
under average load, climatic, and barometric
conditions. However, to fine tune the engine’s
power output, the carburetor may require
adjustments for specific competition needs.
Optional main jets and slow jets are available for
your CRF.  See your Honda dealer.
Any engine or airbox modifications or the use of
an aftermarket exhaust system may require
jetting changes.
Carburetor Components 
Cold Start Circuit
A very rich mixture must be delivered to the
cylinder when cold engine is being started. When
the choke knob (1) is pulled out, fuel is metered
by the starter jet (2) and is mixed with air from
the air passage (3) (located above the throttle
valve (4)) to provide a rich mixture for starting.
The mixture discharges through the orifice (5)
into the cylinder.
(1) choke knob (4) throttle valve
(2) starter jet (5) orifice
(3) air passage
Hot Start Circuit
A lean mixture must be delivered to the cylinder
when a hot engine is being started. When the hot
start lever is pulled back, the hot start valve (1)
opens, allowing air to be supplied to the main
bore (2) through the hot start air passage (3). This
extra air enters the air-fuel mixture from the slow
circuit resulting in a lean condition.
(1) hot start valve
(2) main bore
(3) hot start air passage
3
(1)
(5)
(2)
(4)
(3)
(2)
(1)
(3)
(cont’d) 
						

							Carburetor Adjustments & Tuning Tips
116Adjustments for Competition
Accelerator Pump Circuit
The accelerator pump circuit operates when the
throttle is opened. As the throttle valve (1) opens,
the pump rod (2) depress the diaphragm (3). At
this time, the inlet check valve (4) is shut
resulting in a sharp increase in pressure in the
pump chamber (5). The outlet check valve (6)
then opens, supplying fuel to the main bore via
the accelerator nozzle (7).
(1) throttle valve (5) pump chamber
(2) pump rod (6) outlet check valve
(3) diaphragm (7) accelerator nozzle
(4) inlet check valve
Slow Circuit
Fuel is metered by the slow jet (1) and mixed
with air from the air passage (2). The mixture
enters the venturi through the bypass (3) and
pilot outlet (4) that has been metered by the pilot
screw (5).
(1) slow jet (4) pilot outlet
(2) air passage (5) pilot screw
(3) bypass
Main Circuit
Fuel is metered by the main jet (1), jet needle (2)
and needle jet (3). It is then mixed with air
coming from the air jet (4) and enters the venturi
past the needle jet. 
Baf
fle Plate
The baffle plate (5) prevents foaming of fuel or
abnormal fuel level around the main jet. 
Float Bowl
The float (6) and float valve (7) operate to
maintain a constant level of fuel in the float
bowl.
(1) main jet (5) baffle plate
(2) jet needle (6) float
(3) needle jet (7) float valve
(4) air jet
(3)
2
(1)
(7)
(6)(2)
(5)
(4)
(3)
(2)
(1)(5)
(4)
(6)
(4)
(2)
(7)
(5)
(1)
(3)