O.S. Engines 55HZ-R - Manual (Page 12)

22
Fuel tank
Fuel Stopper
(commercially available)
Fuel Filter
(commercially available)
Check valve
Check valve
Fuel Stopper (commercially available)
T Nipple
Remove when refuelling
(commercially
available)
Be aware of direction
Grooved part should
face the fuel tank.
Silicone tubing
approx.10cm
(commercially
available)
JA PA
N
23
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.
The High-Speed (Main) 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 Idle Mixture Control Screw
This provides the means of manually adjusting the
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.
Three adjustable mixture controls are incorporated in the
Type 40L-R. They are as follows.
A
B
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. C
Idle MIxture Control Screw
High Speed Needle Valve
(Main Needle)
Medium Speed Needle Valve
NOTE
90 degrees 90 degrees
As the idle mixture control screw is installed with
LOCTITE, it may initialy feel stiff, and it is suggested
to use a slightly 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.