DURING BREAK IN...
• Special break-in fuels are not required.
• Drive the model on a smooth hard surface.
• If possible, avoid running on very hot, humid days.
• Run with the body off for extra engine cooling.
• Do not allow the fuel tank to run completely empty, possibly
leading to a burned plug. An extremely low fuel level causes
the fuel mixture to be too lean.
• Keep extra glow plugs handy. The break-in process, because
of the engine running rich, can cause deposits to form on the
glow plug, leading to failure.
• Turn the mixture screw (needle) clockwise (in) to lean the mix-
ture and counter-clockwise (out) to richen the mixture.
THE FIRST TANK OF FUEL
• Drive the Nitro Stampede on a flat paved surface in an oval con-
figuration. This will cause you to naturally vary your speed over the
entire RPM range. During this break in time, ease in and out of the
throttle slowly to avoid stalling the engine. The goal is to simply
keep the engine running.
• The fuel mixture setting may require slight adjustment to correct
for different altitudes and temperatures. To tell if the engine is running
rich (high volume of fuel flowing through the engine) look for the
following conditions:
1) The engine should accelerate sluggishly
2) There should be a thick trail of blue smoke coming
from the exhaust.
• If you do not observe the conditions above, then turn the high
speed needle out 15° (counterclockwise) and retest.
• Do not run at full speed during the first tank of fuel.
•
Do not rev the engine with the wheels off the ground.
High,
no-load RPMs can damage the engine,
usually resulting in a
broken connecting rod
. At the end of the first tank of fuel, stop
the engine and allow it to cool for 5-10 minutes before proceeding.
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 com-
plete. Now its time to tune the engine for maximum power.
• Turn the mixture screw in (clockwise) 1/16 of a turn and continue
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 5). 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 truck for several minutes until the engine is in its
normal 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 truck should accelerate quickly from a standing start with-
out bogging. The idle should be smooth and consistent. Lean
the mixture 1/8 of a turn (clockwise) and re-test. If you experi-
ence 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.
7
2
1
/
2
turns out
2 turns out
Contact Traxxas for assistance: 1-888-TRAXXAS.
972-265-8000
(outside USA). E-Mail us at
LEAN
RICH
SAFE RANGE
Optimum
for High-Speed
Performance
Optimum
for Climbing
& Low Speed
Operation
RACING
EVERYDAY
RUNNING
High-Speed Power Loss
Overheating
Sluggish Performance
Break-In Settings
DANGER
