Suzuki RM250 Owner's Service Manual page 49

4-4 MACHINE TUNING
Needle Clip Position
1
Lean
2
3
4
Rich
5
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.
Air/fuel mixture Needle type and clip position
Lean
Rich
Needle
clip
NECH-1st
NEDH-1st
NECH-2nd
NEDH-2nd
NECH-3rd
NEDH-3rd
NECH-4th
NEDH-4th
NECH-5th
NEDH-5th
Jet Needle
O.D. of Needle
Needle number
NEDH
O.D.
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.
Air/fuel mixture Needle Number
Lean NECL/NEDL
NECK/NEDK
NECJ/NEDJ
NECW/NEDW
NECG/NEDG
Rich NECF/NEDF
Main Jet
The main jet, like the slow jet, meters fuel flow.
Each jet size is indicated by a number. Larger num-
ber means a larger bore diameter and fitting a
larger numberd main jet enriches the air/fuel mix-
ture.
Clip
O.D.
2.765 mm
2.755 mm
2.745 mm
2.735 mm
NECH 2.725 mm
NEDH 2.725 mm
2.715 mm
2.705 mm