Suzuki RM85 Owner's Service Manual page 50

As shown below, each tuning 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 carburetor 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
NEEDLE JET
NEEDLE CLIP POSITION
SLOW JET AND AIR SCREW
THROTTLE OPENING
1 MAIN SYSTEM 2 INTERMEDIATE SYSTEM 3 PILOT SYSTEM
When performing carburetor turning 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 pilot jet meters the fuel supplied to the pilot sys-
tem. Each jet size is indicated by a number. Larger
number means a larger bore diameter and fitting a
larger numbered pilot jet enriches the air/fuel mix-
ture.
THROTTLE VALVE OPENING
1/8 1/4
AIR SCREW
AIR SCREW
The pilot air screw is located in the inlet air passage
and meters the air for the pilot 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 and
1/4 turns out.
JET NEEDLE
When the throttle opening is 1/4 to 3/4, the air/fuel
mixture ratio varies depending on the fuel volume
which the vacuum at the needle jet draws through
the needle jet-to-needle clearance.
MACHINE TUNING
1/2 3/4
Rich
Lean
4-3