Honda CR250R 2004 Owner's Manual page 52

8. Remove the screw from the float bowl, then remove
the float bowl. Change the jets as required.
(1) MAIN JET
9. Reinstall the float bowl and its plug.
CAUTION:
•
Make sure to install the float bowl correctly, with
the overflow hose fitting facing the rear of the
motorcycle.
10. Remove the carburetor top, throttle valve and cable
holder (page 47), and then change the jet needle clip
position as required. Reinstall the jet needle, throt-
tle valve, cable holder and carburetor top.
11. Turn the carburetor upright and tighten its clamp
screws.
12. Install the drive sprocket cover.
13. Adjust the air screw opening as required. Recon-
nect the fuel line at the carburetor.
14. Repeat steps 2 through 11 until the engine gives
maximum power with the correct spark plug read-
ing. It is always better to jet a little rich than a little
lean. It is advisable to record the settings, course
conditions, lap times, and climatic and barometric
conditions for future reference.
NOTE:
•
Be careful not to damage around the throttle
sensor.
•
Do not assemble or move the carburetor with holding
the throttle sensor lead.
Circuit Adjustments
The carburetor has several major circuits, each provid-
ing the fuel/air mixture over a given portion of throttle
valve opening.
These major circuits overlap as shown below.
MAIN JET
JET NEEDLE (TAPERED SECTION)
JET NEEDLE
(STRAIGHT SECTION)
SLOW JET AND AIR SCREW
FULLY 1/4 1/2
1/8
CLOSED
•
Main Jet
The main jet affects fuel/air ratio at full throttle (4/4).
The size should be reduced at higher altitudes.
NOTE:
•
Honda carburetor jet sizes are numbered in in-
crements of 10. When changing the main jet size,
increase or decrease it gradually until the desired
jetting is obtained. Because your CR's jet size num-
bers do not correspond with other carburetor
manufacturer's jet size numbers, use genuine 2003
Honda CR250R jets.
•
Jet Needle
The jet needle controls fuel/air mixture over 1/16 to 1/8
throttle. The straight section affects throttle response
at smaller throttle openings. By changing the position of
the clip in its groove, you can improve acceleration at
medium low and medium speed.
LEANER 1st
2nd
3rd
4th
5th
RICHER
3/4 FULLY
OPENED
(1) CLIP (2) STRAIGHT SECTION
•
Slow Jet and Air Screw
Refer to Carburetor Minor Adjustments (Page 36).
49