EN
7
LOSI 8IGHT/8IGHT-T RTR • INSTRUCTION MANUAL
NOTICE:
Measure engine temperatures at the top of the head.
Low-Speed Adjustment
The low-speed adjustment affects the idle and slightly-off-idle performance. The model
should 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-speed 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
enriched 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-speed 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 enrich 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.
NOTICE:
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
adjust the mixture
by turning the high-speed needle counterclockwise at least “two hours” and be
prepared for further adjustments before running any more.
Engine Tuning
Testing the Temperature
In order to obtain an accurate temperature reading from the engine, stop the car in
a safe area, and let the engine idle for 10 seconds. Once the temperature stabilizes,
this is the true engine temperature. The ideal operating temperature for the engine
will vary with the air temperature but, in general, it should fall within the 220–265°F
(104–129°C) range. A simple way to check the engine temperature is to put a few
drops of water on the top of the head/heat sink. It should take 3−5 seconds for the
water to evaporate. If it boils away quickly, the engine is overheating and the high-
speed needle needs adjusted (turned counterclockwise) at least two hours. The engine
runs cooler while driving because air is passing through the fins on the head, thereby
cooling the engine.
Low-Speed Needle
As you turn this clockwise (leaner), less fuel enters the engine. Turning it
counterclockwise (richer) allows more fuel to enter the engine.
Richer
Leaner
High-Speed Needle
As you turn this clockwise (leaner), less fuel enters the engine. Turning
it counterclockwise (richer) allows more fuel to enter the engine.
Idle-Speed Adjustment
As you turn this clockwise, the carburetor opens wider at idle thereby
increasing idle speed. Turning it counterclockwise decreases the
opening and decreases idle speed.
Richer
Slower
Faster
Leaner
