Carburetor Controls - O.S. engine MAX-32SX-H Series Owner's Instruction Manual

CARBURETOR CONTROLS

With a fixed-wing model, power failure is rarely a
serious threat to the safety of the aircraft since it can
usually glide down to a safe landing. In a helicopter,
on the other hand, it is vitally imporant that the engine
keeps running and that there is a quick and reliable
response to the throttle in order to ensure safe ascent
and descent of the model.
Two adjustable controls are provided on this carburetor.
•
The Needle Valve:
When set to produce maximum power at full throttle,
this establishes the basic fuel/air mixture strength.
This is then maintained by the carburetor's
automatic mixture control system to cover the
engine's requirements at reduced throttle settings.
•
The Mixture Control Valve (Mixture ControlScrew):
For adjusting the mixture strength at part-throttle
and idling speeds, to obtain steady idling and
smooth acceleration to medium speeds. The Mixture
Control Valve has been factory set for the
approximate best result. First, run the engine as
received, and re-adjust the Mixture Control Valve
only when necessary.
REALIGNMENT OF MIXTURE CONTROL VALVE
In the course of making carburetor adjustments, it is
just possible that the Mixture Control Valve may be
inadvertently screwed in or out too far and thereby
moved beyond its effective adjustment range.
Its basic setting can be reestablished as follows :
The basic ( factory ) setting is as shown in the main
sketch, i. e. with the shoulder portion 'A' exactly at a
tangent to the throttle rotor hole.To return the Mixture
Control Valve to its original position, first screw in the
Mixture Control Valve, while looking into the rotor hole.
Then gradually unscrew the Mixture Control Valve
until 'A' is precisely tangential to the rotor hole (i.e. so
that 'A' and 'B' are superimposed) as in the main
sketch.
Needle Valve
Mixture Control Valve
(MIxture Control Screw)
Rotor Guide Screw
Throttle Lever
12
Mixture Control Valve
(MIxture Control Screw)
Nozzle
Throttle Rotor Hole