Chassis Adjustments For Track Conditions; Rear End; Fork Height/Angle; Wheelbase - Honda CR250R 2004 Owner's Manual

7. CHASSIS ADJUSTMENTS FOR TRACK CONDITIONS

Rear End

If you have a problem with rear wheel traction, you can
run a little bit more preload on the spring. Instead of
running 3.9 in (100 mm) of sag, you can run 3.5 in (90
mm) so the rear of the bike will sit a little higher. This will
give you more traction because of the angle of the
swingarm and the location of the Center of Gravity.
By contrast, you may have a problem with the steering
head shaking when there is lots of front braking to do.
Or, maybe the bike wants to turn too quick on you. Then
you want to lower the rear of the bike. Reducing the
rear spring preload will increase fork rake and trail so
stability in a straight line is improved.

Fork Height/Angle

The position of the outer tubes in the clamps is
not adjustable. Align the groove in the outer tube with
the top surface of the upper fork clamp.
If you install the optional 20 inch wheel, align the top of
the fork tube with the top of the upper fork clamp.
(STANDARD POSITION)
(1) GROOVE
(2) UPPER FORK CLAMP
(3) STANDARD POSITION
0.3 in (7 mm)
(STANDARD POSITION FOR OPTIONAL FRONT WHEEL)
(1) TOP OF FORK TUBE
(2) UPPER FORK CLAMP
(3) STANDARD POSITION
FOR OPTIONAL
FRONT WHEEL
0 in (0 mm)
74
NOTE:
•
Never position the top surface of the triple clamp
more than 0.1 in (2 mm) below the top of the outer
tube.
•
Do not include the fork bolt thickness, or the cham-
fered edge of the tube in the height measurement.

Wheelbase

You may run the chain adjustment on the swingarm
most of the way to the front or out toward the rear of the
adjustment range and add or remove links as neces-
sary. With the axle up toward the front, you will get a
little bit better traction. If there are a lot of fast sections,
then it may be better to run a little longer wheelbase. On
a track with a lot of fast rollers, the long wheelbase
works good. If it is a tight track, like a supercross track,
usually a shorter wheelbase is better. Especially if the
traction is poor. The shorter wheelbase also transfers
more weight to the rear to help the bike hook up better
and wheelie easier.
You can use these wheelbase adjustments for more or
less trail as mentioned eariler.
You must realize that these chassis adjustments offer
subtle changes in overall handling, yet a noticeable
improvement will be realized in the areas specified.
If you change your wheelbase, be sure to recheck race
sag and adjust, if necessary.

8. GEARING SELECTION

Explanation Of Effects On Power Delivery & Traction
Rather than counting on frequently unreliable, after-
market engine modifications for improved perform-
ance, you should first try to "adjust" the power delivery
of the standard engine to suit the terrain and course
conditions. The easiest way to do this is to change
gearing, which allows you to utilize a different portion
of the engine's power range.
The portion of the power range you use can be adjusted
most efficiently by changing the final drive ratio with
optional sized rear sprockets. This way the power
delivery can be more closely matched to the available
traction, which changes from day to day, and to the
type of terrain the course offers. Similarly, the number
of shifts needed per lap, or for specific and critical
sections, can be "adjusted" in order to reduce lap times
with a simple sprocket change.
These optional driven (rear wheel) sprockets are of-
fered in increments of two teeth less, or more, than the
standard sprocket. This small difference is enough to
allow you to "tune" the engine for the available traction
without creating drastic changes in the top speed
potential of the machine.
— Higher gearing (less rear sprocket teeth) will produce
less power to the ground and allow the rear wheel to
hook-up when the track is slippery (wet, sandy, loose
dirt on clay base, etc.).
— Lower gearing (more rear sprocket teeth) will pro-
duce more power to the ground and allow you to utilize
maximum traction conditions.