10
TANKS TWO-FOUR
Turn the high-speed mixture screw clockwise 15
0
and run
through the second tank of fuel. Repeat this process for the third
and fourth tanks of fuel.
Important: Do not lean the high speed mixture less than 2
turns out from closed (see illustration). Also, be sure to
allow the engine to cool between each run.
TANK FIVE AND BEYOND
• All final tuning adjustments must be made to the engine at its
normal operating temperature.
• The engine’s performance depends on the fuel mixture. Leaning
the fuel mixture with the high-speed needle (turning clockwise)
will increase engine power up to engine’s mechanical limits.
Leaning the fuel mixture beyond the safe allowable limits will
result in poor performance and engine damage.
• After the fourth tank of fuel, the break in process should be
complete. Now its time to tune the engine for maximum power.
• Turn the mixture screw in (clockwise) 1/16 of a turn and contin-
ue driving. Note any increase in speed and performance.
• Continue to lean the fuel mixture in 1/16 turn increments until :
1) There is no longer any performance increase or
2) The engine begins to cut out at high speed or
3) The engine begins to overheat. Symptoms include:
• Steam or smoke coming from the engine surfaces
• Hesitation during acceleration (as if running out of fuel)
• Popping or clattering sound when decelerating (detonation)
• The idle speed will fluctuate
• Any of the above symptoms indicate that the fuel mixture is past
the maximum safe lean setting. Turn the mixture screw back out
(counterclockwise) the previous 1/16 of a turn to reach the optimum
fuel mixture setting.
• Turn the mixture screw out another 1/16 of a turn for non-race
applications. This will extend engine component life. This setting
will vary slightly with each engine depending upon fuel brand,
temperature, humidity, etc.
FINE TUNING THE LOW-SPEED MIXTURE
The low-speed mixture screw is located in the end of the throt-
tle shaft (see the drawing on page 7). The low speed mixture
affects the idle quality and the low end engine power and throttle
response. To check your low speed mixture setting, perform this
simple test.
1) Drive the car for several minutes until the engine is in its nor-
mal operating temperature range.
2) Pull it in, stop, and listen to the idle speed. If, after a few seconds,
the idle speed begins to drop then lean the low speed mixture
1/8 of a turn (clockwise) and retest.
3) Continue leaning the engine in small steps until the idle speed
will stay even for at least 20-30 seconds after stopping.
4) The car should accelerate quickly from a standing start without
bogging. The idle should be smooth and consistent. Lean the
mixture 1/8 of a turn (clockwise) and re-test. If you experience
any stalling or hesitation when accelerating, then the low
speed mixture is too lean. Richen it 1/8 of a turn (counter
clockwise) and retest.
SETTING THE IDLE SPEED
Now that the engine mixture is tuned, the idle speed may be
set too high. Only set the idle speed when the engine is at its nor-
mal operating temperature. Adjust the throttle trim on the transmit-
ter so that the brake on the car is
applied. Next, reset the idle speed by
removing the air filter and adjusting
the idle speed screw on the side of
the carburetor (see drawing on page
7). Turn the screw out (counter-
clockwise) to reduce the idle. Re-
adjust the throttle trim on the trans-
mitter as necessary (so that the
brake is no longer applied). The idle
should be set slow enough that the
car does not try to move at idle.
ADJUSTMENTS
• SHIFT POINT ADJUSTMENT
The Nitro 4-T
ec
comes equipped
with a two-speed transmission. When
the shift point on this transmission
is adjusted correctly, it will maxi-
mize acceleration, improve drivabili-
ty, and minimize lap times. Use a
2.0mm allen wrench to adjust the
shift point.
NOTE: It is important that your
engine is properly tuned and has
Contact Traxxas for assistance: 1-888-TRAXXAS. 972-
265-8000
(outside USA). E-
m
ail us at support@
T
raxxas.com
Positive camber
Negative camber
TOE IN
PRE-LOAD
SPACERS
Access hole
Drum
