4-4 MACHINE TUNING
NEEDLE CLIP POSITION
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
3rd 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. To change the needle clip
position by half, change jet needle from 24NAAH
type to 24NCDH type. This change will move the
needle position by half to the leaner side.
JET NEEDLE
NEEDLE NUMBER
Changing the needle itself controls air/fuel mixture
ratio particulary on lower mid-throttle opening. The
smaller the O.D., the richer the air/fuel mixture
becomes.
MAIN JET
The main jet, like the pilot jet, meters fuel flow.
Air/fuel mixture Needle type and clip position
Lean
24NCDH-1st
24NAAH-1st
24NCDH-2nd
24NAAH-2nd
24NCDH-3rd
24NAAH-3rd
24NCDH-4th
24NAAH-4th
24NCDH-5th
Rich
24NAAH-5th
Lean
Rich
Needle
clip
1
2
3
4
5
Air/fuel
mixture
Needle Number O.D.
Lean
24NAAK/24NCDK 2.415 mm
24NAAJ/24NCDJ 2.405 mm
24NAAH/24NCDH 2.395 mm
24NAAG/24NCDG 2.385 mm
Rich
24NAAF/24NCDF 2.375 mm
O.D. of Needle
Clip
24NAAH
O.D.
128
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