Suzuki RM125 Owner's Service Manual page 49

4-4 MACHINE TUNING
NEEDLE CLIP POSITION
Lean
Rich
The jet needle is linked to the throttle valve by
means of the needle clip. Its lower part is tapered
and it has five grooves cut in the upper part where
the needle clip fits.
To adjust the air/fuel mixture with the jet needle,
change position of the needle clip which is set in the
4th groove. The lower groove the clip is moved to,
the higher the jet needle rises and the larger the
clearance with the needle jet becomes, resulting in
a richer air/fuel mixture ratio.
The needle clip position can be changed by half to
fine-tune the setting as following manner.
• Replace the cable holder with the included holder
and included red washer.
The two holders are different in color. The stan-
dard holder is gray. The included holder is yel-
low. The included holder and red washer must be
installed as a set.
• Change the red washer location from over the
needle clip to under the needle clip. This change
will move the needle position by half to the richer
side. The original position of red washer is over
the needle clip.
By replacing the jet needle with the optional one, it
is possible to perform the same setting as describ-
ing above. Change the jet needle from 6CHY17
type to 6CHY16 type. This change will move the
needle position by half to the richer side. 6CHY16
type jet needles are available as optional parts.
For example, "6CHY17-65-3rd" with the red washer
installed under the needle clip is the same setting
as "6CHY16-65-3rd".
Needle type and clip position
Lean
Rich
Needle
clip
6CHY17-65-2nd
6CHY16-65-2nd
6CHY17-65-3rd
6CHY16-65-3rd
6CHY17-65-4th
6CHY16-65-4th
JET NEEDLE
Taper portion
NEEDLE NUMBER
6CHY17-65-3rd
O.D. 2.65 mm
Changing the needle itself controls air/fuel mixture
ratio particulary on lower mid-throttle opening. (Size
65 indicates that O.D. is 2.65 mm) The smaller the
O.D., the richer the air/fuel mixture becomes.
EX.
Needle Number
6CHY17-66
6CHY16-66
6CHY17-65
6CHY16-65
6CHY17-64
6CHY16-64
6CHY17-63
6CHY16-63
6CHY17-62
6CHY16-62
6CHY17-61
6CHY16-61
6CHY17-60
6CHY16-60
MAIN JET
The main jet, like the pilot jet, meters fuel flow. Each
jet size is indicated by a number. Larger number
means a larger bore diameter and fitting a larger
number main jet enriches the air/fuel mixture.
O.D. of needle
Clip
O.D.
2.66 mm
2.65 mm
2.64 mm
2.63 mm
2.62 mm
2.61 mm
2.60 mm