Carburetor Minor Adjustments - Honda 2005 CRF450R Owner's Manual

Carburetor Adjustments & Tuning Tips

Carburetor Minor Adjustments

The standard carburetor settings are ideal for the
following conditions: sea level altitude, and 68°F
(20°C ) air temperature. If your conditions are
different, you may need to adjust the carburetor
settings, using the tuning information on pages
124 and 125. Confirm your settings are correct
before proceeding.
Minor Adjustments
1. Adjust the carburetor setting using the tuning
information on pages 124 and 125.
2. When the engine is warm enough to run
without the choke, push the choke knob in to
its off position.
3. Adjust the pilot screw (1) to obtain the best
off-idle performance.
– If the engine blubbers (rich) exiting a
corner, turn the pilot screw clockwise to
lean the mixture.
– If the engine surges (lean) exiting a corner,
turn the pilot screw counter clockwise to
richen the mixture.
The minimum to maximum range of pilot screw
adjustments is 1 1/4 to 2 turns out from the
lightly seated position. If you exceed 2 turns out,
the next larger slow jet is needed. If you are
under 1 1/4 turn out, the next smaller slow jet is
needed.
126
Adjustments for Competition
(1)
(1)
(1) pilot screw
Adjustment Procedure
1. Warm up the engine.
2. Make two or three laps of a course with the
standard setting or corrected jetting (page
124). and spark plug. Note engine
acceleration and other engine conditions in
relation to throttle opening. Verify
carburetion by removing the spark plug and
reading its firing end (page 128). It may take
more than two or three laps to get a good
spark plug reading with a new spark plug.
3. Change carburetor settings or select suitable
carburetor jets, taking into consideration the
engine conditions and factors for temperature
and altitude (page 124).
WARNING
Gasoline is highly flammable and
explosive. You can be burned or
seriously injured when handling fuel.
• Stop the engine and keep heat, sparks
and flame away.
• Handle fuel only outdoors.
• Wipe up spills immediately.
4. Turn the fuel valve OFF.
5. Drain the remaining fuel in the float bowl by
loosening the drain screw (2) and disconnect
the fuel line from the fuel valve.
6. Loosen the connecting and insulator band
screws. Rotate the carburetor. Remove the
float bowl plug (3).
Make sure the float bowl plug O-ring (4) is in
good condition, and replace it if necessary.
(3)
(2) drain screw (4) O-ring
(3) float bowl plug
(2)
(4)