Losi LOSB0125 - Manual (Page 10)

10
About Glow Plugs
The glow plug is like the ignition system in your automobile.
The coiled element in the center of the plug glows red hot
when connected to a 1.5-volt battery (located in the igniter).
This is what ignites the fuel/air mixture when compressed in
the cylinder. After the engine fires, the heat generated by the
burning fuel keeps the element hot. Common reasons for the
engine not starting are the 1.5-volt battery being weak, the
glow plug being wet with fuel, or the element burned out. Use
a spare glow plug to check the igniter. If the igniter makes the
element glow, remove the plug from the engine to check it in
the same manner. A wet glow plug means there is excess fuel in
the engine. To eliminate this, put a rag over the head and turn
the engine over a few seconds with your Spin-Start. Reinstall
the glow plug, making sure you have the brass gasket on it. The
engine should now start.
Testing the Temperature
The ideal operating temperature for an engine will vary with
the air temperature but in general it should be in the 190° to
230°F (88 to 110° C) range. Since the Speed-NT has a head
protector you will have to rely on your ears or preferably
a remote temperature gauge like the Losi Temp-Tuner ™
(LOSA99171) which incorporates an infrared temp sensor/
gauge and a handy carburetor tuning screwdriver. If the
engine is overheating turn the high-speed needle out (counter
clockwise) at least two hours. If the engine is running rich
(below 190° F) turn the high-speed needle in (clockwise) one
hour at a time until it is running within the normal range.
Low-Speed Adjustment
The low-speed adjustment affects the idle and slightly-off-idle
performance. The optimum setting allows the motor to idle
for at least 8−10 seconds. The model should then accelerate
with a slight amount of sluggishness and a noticeable amount
of smoke. The simplest way to check this is to make sure the
engine has been warmed up and let the engine idle for 8−10
seconds. If the low-speed mixture is so far off that the engine
won’t stay running that long, turn the idle stop screw clockwise,
increasing the idle speed. With the engine at idle, pinch and
hold the fuel line near the carburetor, cutting off the flow of
fuel, and listen closely to the engine rpm (speed). If the low-
speed needle is set correctly, the engine speed will increase
only slightly and then die. If the engine increases several
hundred rpm before stopping, the low-speed needle is too rich.
Lean the mixture by turning the needle clockwise one hour and
trying again. If the engine speed does not increase but simply
dies, the needle is too lean and needs to be richened up by
turning the needle counterclockwise one hour before trying
again. After you have optimized the low-speed setting, the
engine will probably be idling faster. You will have to adjust the
idle stop screw counterclockwise to slow the engine idle speed
down. The engine should accelerate at a constant pace without
hesitating.
High-Speed Adjustment
After initial acceleration, the engine should pull at a steady rate
while maintaining a two-stroke whine and a noticeable trail of
smoke. If the engine labors and is sluggish with heavy smoke,
the mixture is too rich and needs to be leaned by turning the
high-speed needle clockwise in one-hour increments until it
runs smoothly. If the engine isn’t smoking or starts to die after
acceleration, it is too lean and you must richen the mixture by
turning the needle counterclockwise. Don’t be confused by
the sound of the engine and the actual performance. A leaner
mixture will produce an exhaust note with a higher pitch but
this does not necessarily mean improved performance, as the
engine is on the verge of overheating and may incur possible
damage. Ideally you want to run the engine so that it is on
the slightly rich side of optimum. This will give you the best
combination of speed and engine life.
CAUTION : The engine
is too lean and overheating if it accelerates rapidly with a
high-pitched scream then seems to labor, stops smoking, or
loses speed. This can be caused by the terrain, atmospheric
conditions, or drastic altitude changes. To avoid permanent
engine damage,
immediately richen the mixture by turning
the high-speed needle counterclockwise at least “two hours”
and be prepared for further adjustments before running any
more.
Note : The normal operating temperature as seen on
your radio screen should be in the 190 to 220° F (88 to 105° C)
range.