Carburetor Controls - O.S. engine MAX-91SZ-Hring 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.
Three adjustable mixture controls are incorporated in the
Type 60M-C. They are as follows.
The High-Speed (Main) Needle Valve
A
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.
B
The Idle Mixture Control Screw
This provides the means of manually adjusting the
60M's mixture control valve. By setting the Mixture
Control Screw for the best idling performance, the
mixture control valve automatically ensures that fuel is
accurately metered to maintain the correct mixture
strength as the throttle is opened.
BASIC POSITION OF MIXTURE CONTROL SCREW
(Mixture Control Valve)
As delivered, the Mixture Control Screw is
positioned at approximately the center as shown in
the sketch.
Mixture gets lean when the Mixture Control Screw
is turned right, while mixture gets rich when the
Mixture Control Screw is turned left.
With a model helicopter, adjustments vary with
combined various factors such as climatic
conditions, fuel, muffler, main rotor, weight of the
model, gear ratio, etc. Therefore, Mixture Control
Screw position varies with each model and set- up,
and it is normal if the Mixture Control Screw
position is off the center.
MIxture Control Screw
Thick
C
18
Lean
Mixture Control Valve
19
The Medium Speed Needle Valve
This is an extra control that can be brought into
play, if necessary, after adjusting A and B above. It
provides the means of fine-tuning mixture strength
over that all-important part of a helicopter's throttle
range where the model is flying in, or near, the
hovering mode.
Idle MIxture Control Screw
High Speed Needle Valve
(Main Needle)
Medium Speed
Needle Valve
NOTE
As the idle mixture control screw is installed with
LOCTITE, it may initialy feel stiff, and it is suggested
to use a littli oversized screwdriver. The screw can be
turned only 90 degrees either way. Do not force to turn
further, or it may break or cause trouble.
90 degrees
90 degrees
GRADUATIONS ON THE CARBURETOR BODY
As shown in the sketch, the carburetor has
graduation marks.
Fully opened position
89 degrees
Fully closed
position
Carburetor Rotor
Carburetor Body
When the triangle mark on the carburetor rotor meets
the far right mark, the throttle is fully closed. When
the triangle mark meets the top mark, the throttle is
fully open. The range is 89 degrees. You may use
the other three marks as the reference marking of
throttle opening to your preference when hovering.
WARNING!
Never try to check the triangle mark position
while the engine is running and rotor is
rotating, or you may be hit by rotating rotor which
results in serious injury. Stop the engine and
rotor before checking the triangle mark position.
Needle
Adjusting screw