Suzuki RM 250 2003 Owner's Service Manual page 87

9-4 FUEL SYSTEM
As shown below, each of the asterisk (*) marked parts is located between the air/fuel passage and has its
own air/fuel mixture adjustable range in terms of the throttle valve opening. The chart indicates that the car-
buretor can supply correct air/fuel mixture to the engine in any range because of the overlapping adjustable
range of the each part.
TUNING PARTS
MAIN JET
JET NEEDLE CLIP POSITION
JET NEEDLE O.D.
SLOW JET AND AIR SCREW
POWER JET
THROTTLE OPENING
1 MAIN SYSTEM 2 INTERMEDIATE SYSTEM 3 SLOW SYSTEM
When performing carburetor tuning first find out in
what throttle opening range an improper air/fuel
mixture is supplied, by checking the color of
exhaust smoke, spark plug, throttle response,
power, etc. Second, replace or adjust the part(s)
related to the throttle opening range by referring to
the following instructions. The sizes referred to in
the illustrations are those of standard setting.
Slow Jet
The slow jet meters the fuel supplied to the slow
system. Each jet size is indicated by a number.
Larger number means a larger bore diameter and
fitting a larger numbered slow jet enriches the
air/fuel mixture.
THROTTLE VALVE OPENING
1/4 1/4 1/2
Air Screw
Rich
The air screw is located in the inlet air passage and
meters the air for the slow system. As it has a
right-hand thread, tightening it makes the passage
narrower, allowing less amount of intake air to flow
and resulting in richer air/fuel mixture. Air flow
adjustment is effective within a range of 1/2 – 2
turns out.
Power Jet
The power jet supplies the necessary amount of
fuel to the carburetor bore for correcting fuel/air
mixture ratio. When engine speed is 2 000 to 3 000
rpm and 9 300 to 10 500 rpm, the passage is
closed by solenoid valve. The solenoid valve closes
the passage when the current flows from CDI unit.
3/4
Lean