14
FUEL
PROPELLERS
Suggested propeller sizes are listed on page 15. The
suitability of the prop depends on the size and weight
of the model and type of flying. Determine the best
size and type after the engine has been run in. Check
the balance of the propeller before fitting it to the
engine. Unbalanced propellers cause vibration and
loss of power. Wooden propellers are to be preferred.
Some nylon propellers are not strong enough to
withstand the high power output of these engines
and a thrown blade can be very dangerous.
Model engine fuel is poisonous. Do
not allow it to come into contact with
the eyes or mouth. Always store it in a
clearly marked container and out of
the reach of children.
Model engine fuel is also highly flam-
mable. Keep it away from open flame,
excessive heat, sources of sparks, or
anything else which might ignite it.
Do not smoke, or allow anyone else to
smoke, near to it.
Select, by practical tests, the most suitable fuel from
among the best quality fuels available in your country
for model use. For the best performance, a fuel
containing 5% to 20% nitromethane is preferable.
Lubricants may be either castor-oil or a suitable
synthetic oil ( or a blend of both ) provided that they
are always of top quality.
For consistent performance and long engine life, it is
essential to use fuel containing AT LEAST 18%
lubricant by volume. Some fuels containing coloring
additives tend to deteriorate and may adversely affect
running qualities.
Once a satisfactory fuel has been selected and used
for a while, it may be unwise to needlessly change
the brand or type. In any engine, a change of fuel
may cause carbon deposits in the combustion
chamber or on the piston head to become detached
and lodged elsewhere, with the risk of this causing
unreliable operation for a while. If, however, the
adoption of a different fuel is unavoidable, check the
engine for the first few flights on the new fuel, by
temporarily reverting to the running-in procedure.
Reminder!
Reminder!
15
MIXTURE CONTROLS
10.5x6, 11x6-8, 12x6-7
Sport
Never touch, or allow any object to come
into contact with, the rotating propeller and
do not crouch over the engine when it is
running.
Reminder!
The Needle Valve (at rear of engine)
When set to produce maximum power at full
throttle, this establishes the basic fuel/air mixture
strength. The correct mixture is then maintained by
the carburetor's built-in automatic mixture control
system to cover the engine's requirements at
reduced throttle settings.
The Mixture Control Valve (carburetor)
This meters fuel flow at part-throttle and idling
speeds to ensure reliable operation as the throttle
is opened and closed. The Mixture Control Valve is
factory set for the approximate best result. First run
the engine as received and readjust the Mixture
Control Screw only if necessary.
Two mixture controls are provided on this
Carburetor.
