IAME REEDSTER 125cc Assembly Instructions & User Manual page 26

F4 engine vers: "DELL'ORTO VHSH30 CS" CARBURETTOR
The above settings are those prescribed by IAME for the carb. Dell'Orto VHSH 30 CS, installed on the Parilla
REEDSTER engine - in the F4 version.
The above table shows the reference setting, for the proper engine operation under different temperature,
altitude and atmospheric pressure conditions
Should you need an optimized carb. setting, for all atmospheric conditions, it will be necessary to adjust the
setting for a better mixture strength according to the track characteristics and ambient conditions.
In case of a high level setting, for which a specific experience is required, it is impossible to give instructions
in a few words. Our target is to give here simple instructions for setting the best adjustment, according to the
operation conditions.
As a rule, we consider three ranges of operation: the idle RPM and low RPM, attainable with throttle lever
slightly opened; the mid. RPM or intermediate RPM, attainable with intermediate opening of the throttle lever
and the max RPM, attainable with max. opening throttle lever .
In a float chamber carburettor, such as this carburettor, specific devices are available to check the
carburetion at each RPM range of operation; each of these devices intervenes on a specific area as
described hereinafter, even if there is no clear distinction among the different areas.
The idle RPM can be adjusted by means of the "A screw " (see fig.1),
which intervenes on the throttle valve by slightly lifting or and lowering it.
It is necessary to turn clockwise to increase the RPM,
and turn counterclockwise to decrease it.
The carburetion at idle RPM can be set by means of :
•
The idle jet in the float chamber
•
The idle emulsion tube, located above the respective jet
•
The air mixture idle screw
Generally, for standard adjustments, the emulsion tube is not concerned.
A richer mixture can be obtained by increasing the idle "L" jet size (see fig.2),
and a leaner mixture by decreasing the above size.
The idle jet can be reached removing the carb. float chamber.
A richer carburetion is attainable by turning the air screw "B" clockwise
(see fig.1); on the contrary, by unscrewing, you get a leaner
carburetion. It is suggested to gradually perform the adjustment by 5÷10'
turns per time. Then check the result.
The adjustment of the carburation at mid range is performed by means of:
•
The conical needle
•
The needle jet
the conical needle acts as a shutter on the needle jet, and its axial
position is determined by the throttle gas opening.
Thanks to its particular conical configuration, when the throttle opens
gradually, the needle gradually releases the spray nozzle hole and
regulates the gasoline flow.
The conical needle and the spray nozzle have been chosen to satisfy
most of the conditions, and as a rule, it not necessary to replace them
with others having different characteristics. The carburetion setting
is performed by lifting or lowering the needle vs. the throttle gas.
A
24
Fig.1
Fig. is
H
L
MAN-051 ING