Adjusting Fuel Mixture and Compression
This section describes a step-by-step procedure for adjusting fuel mixture and
compression on Norvel engines.
1.
Set your helicopter on the ground with the engine idling. Slide a heavy pole or
wood plank from side to side over the landing gear skids and between the wire
struts in order to weigh your helicopter to the ground. With the helicopter safely
grounded, you can adjust the needle valve at full power. Slowly open the throttle.
If the helicopter lifts into the air, place a heavier weight across the skids.
2.
Move the throttle stick and throttle trim lever on the transmitter to full throttle.
3.
Carefully reach under the rotor blades and slowly open (screw out) the needle
valve until the engine runs roughly (four-strokes). This fuel/air mixture is too rich.
Warning!
MOVE SLOWLY AND CAREFULLY ANY TIME YOU WORK NEAR THE
ROTATING ROTOR BLADES! DO NOT TOUCH THE ROTATING ROTOR
BLADES WITH YOUR HAND OR ARM! ALSO WATCH OUT FOR THE
ROTATING TAIL ROTOR BLADES!
4.
Slowly close (screw in) the needle valve. The engine will run faster and
smoother, and the engine sound will increase in pitch. At some point you will hear
it slow down again. This mixture setting is too lean. The optimum needle valve
setting lies about half way between the rich and lean settings. It is best to operate
with a slightly rich mixture since the engine will run cooler.
5.
Open (screw out) the needle valve to the optimum point half way between the rich
and lean settings.
6.
Close the throttle (throttle trim is still high). The engine should idle smoothly, and
slowly enough that you can hold the main rotor without feeling much clutch drag.
If the engine runs too fast, try reducing throttle trim slightly. If it stops suddenly,
the compression may be too high - add another copper washer under the glow
plug and adjust the needle valve.
BE CAREFUL, THE HEAT SINK IS HOT!
Hint:
Never hold the rotor head while tightening or loosening the heat sink, because
you could bend the main shaft. Instead, hold the crutch near the tail boom
7.
Open the throttle to full, and listen closely to the engine sound. The engine should
smoothly and rapidly increase speed to a maximum. If it sputters and increases
speed slowly or four-strokes (runs rough) it may be slightly rich, so screw
IN
the
needle valve slightly. If it reaches top speed and then sags or “warbles” it may be
lean, so screw
OUT
the needle valve slightly.
Op er a tor's Guide
Glow-Fuel Engines
4-10
LITE MA CHINES
