Honda CRF450R 2011, Руководство пользователя

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Gearing
142
Adjustments for Competition
Gearing
You can “adjust” the power delivery of the
standard engine to suit track conditions by
changing gearing. This allows you to utilize a
different portion of the engine’s power range at a
given throttle setting. New gearing may provide
the change you are looking for without the need to
consider further modifications.
The portion of your engine’s power range you use
can be adjusted by changing the final drive ratio
with different sized rear sprockets. Gearing
changes allow you to more closely match the type
of terrain and the available traction.
Normally, a change of one tooth on the driven
sprocket will be sufficient.
There is a choice of both higher and lower final
drive ratios with two optional driven sprockets.
Like the optional springs, these sprockets are listed
in the Optional Parts List section of this manual
(page 160).
Unless you have the required mechanical know-
how, tools, and an official Honda Shop Manual,
sprocket changing should be done by your Honda
dealer.
Higher Gearing (less driven sprocket teeth)
• increases top speed in each gear (provided the
engine will pull the higher gearing)
• reduces frequency of shifting (wider gear
ratios)
• reduces engine min –1 (rpm) at a given throttle
setting or ground speed (which may allow
better rear wheel traction on slippery or loose
terrain)
However:
• the engine may not pull the higher gearing
• the spacing between gears may be too wide
• engine min
–1 (rpm) may be too low
Lower Gearing (more rear sprocket teeth)
• decrease top speed in each gear
• increases frequency of shifting (narrower gear
ratios)
• increases engine min –1 (rpm) at a given throttle
setting or ground speed (which may provide
more power-to-the-ground on good traction
surfaces)
However:
• spacing between gears may be too narrow
• engine min
–1 (rpm) may be too high
Some tracks may be watered heavily prior to the
first race, then lightly or not at all during the day.
This results in a track surface that is slippery
during the first few races, then changes from good
to great and back to good and possibly ends the day
with a slick rock-hard consistency.
Ideally, your gearing should be adjusted to suit all
these conditions.
• Wet and slippery or sandy conditions: use a
higher gear (less teeth) to keep engine min –1
(rpm) down, and avoid unwanted wheelspin.
The engine may bog in certain corners so
you’ll need to slip the clutch to compensate;
downshifting may be too drastic a change in
speed.
• Average conditions: use the standard sprocket.
• Hard (but not slippery) track conditions: use
lower gearing (more teeth) to keep the engine
min
–1 (rpm) high where the engine produces
the most power. This may require an extra
upshift on certain sections or perhaps you can
just rev it out a bit longer.
For tight tracks, consider lower gearing to avoid
having to slip the clutch frequently. Repeated
fanning or pulling of the clutch lever in a turn to
raise engine min
–1 (rpm) may eventually damage
the clutch system.
A gearing change may help for riding in sand,
where you want to keep the front end light so it can
float from the peak of one sand whoop to the next.
Generally, with higher gearing, it is easier to
maintain that perfect attitude (maximum rear
wheel traction and a light front end) because you
remain in the powerband longer in each gear.
The higher gearing allows you to steer more
efficiently with throttle control and body English.
If you are riding a track with sections where you
choose to over-rev the engine temporarily rather
than shifting up, higher gearing might help.
Sometimes you have to sacrifice performance on
one section of the track to gain a better overall
time. Your goal is the fastest overall lap time, even
if the cost is some sections where the gearing feels
wrong.
If you decide to try a gearing change, have
someone check your times with a stopwatch
(before and after the change) to get an accurate
appraisal of the change. “Seat-of-the-pants”
feelings can’t be trusted. Eliminating wheelspin
with a gearing change can make you feel like
you’re going slower when, in reality, you’ve
decreased your time by increasing your speed with
better traction.
These gearing recommendations should be
evaluated by considering your ability, your riding
style, and the track.
CRF450R.book Page 142 Thursday, July 8, 2010 9:34 AM