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Carburetor controls
Three adjustable mixture controls are incorporated in the type 40L. They are as follows.
A) The High-Speed (Main) needle valve
When set to produce maximum power at full throttle, this established 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 the throttle settings.
B) 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.
C) 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.
NOTE
As the idle mixture control screw is installed with LOCTITE, it may initially 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.
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 the 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.
GRADUATIONS ON THE CARBURETOR BODY
As shown in the sketch, the carburetor has graduation marks.
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. |
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