SLAYER PRO 4X4 • 21
air/fuel mixture ratio and leaning the fuel mixture decreases the
amount of fuel in the air/fuel mixture ratio.
• Slightly lean fuel mixtures deliver stronger, more efficient
combustion and more power, but with less lubrication.
• Slightly rich fuel mixtures deliver cooler running and more
lubrication but with slightly less power.
Tuning the engine means finding the perfect balance between the
two; excellent power to meet your needs while maintaining good
lubrication for long engine life.
The optimal fuel mixture setting is
rich
to provide a safety margin against having a lean condition if some
variable changes (such as the temperature from one day to the next).
General fuel mixture settings are measured by the number of turns
the needles are turned out from fully closed. The fuel mixture settings
have been pre-set from the factory to typical break-in settings. Do
not readjust your carburetor from the factory settings until after the
engine is started and running, and you have been able to observe the
engine running to assess what minor adjustments may be required
to compensate for fuel, temperature, and altitude. Adjustments are
usually made in 1/8 or 1/16-turn increments. If the engine sticks at top
dead center (TDC), see page 35 for instructions on freeing the engine.
The Idle Speed Adjustment
The idle speed adjustment screw controls the closed position of the
throttle slide. When the throttle servo is in its neutral position, the
throttle slide should be stopped against the idle speed adjustment
screw. Always use the idle speed adjustment screw to control engine
idle. See page 27 for instructions on adjusting the idle speed.
THE TRAXXAS Ez-START
ELECTRIC STARTING SYSTEM
The Traxxas EZ-Start brings the convenience of push-button electric
engine starting to your model. The EZ-Start consists of a hand-held
control unit and an on-board motorized starter.
• Power for the EZ-Start system comes from a 7.2-volt rechargeable
battery pack installed in the hand-held control unit.
• The engine glow plug is heated automatically by the EZ-Start system,
eliminating the need to keep up with a separate glow plug igniter.
• The voltage to the glow plug is kept constant, regardless of the load
placed on the starter by the starter motor.
• The “Glow Plug” LED (light emitting diode) on the control unit
indicates the condition of the glow plug.
• The “Motor” LED indicates the status of the EZ-Start electric starter motor.
• The cush drive mechanism in the drive unit prevents damage to the
gears caused by engine kickback.
• Smart Start
™
protection circuitry prevents damage to the motor by cutting
power if the load on the motor or other electronics exceeds safe limits.
Charging the EZ-Start Battery
The included charger can be used to charge the included EZ-Start
battery pack.
1. Plug the charger into the wall. The LED on the charger should
glow green.
2. Connect the included EZ-Start battery pack to the charger output
cord. The LED will glow red, indicating the battery is charging.
3. The battery should charge for approximately 4
½
hours. The LED
will turn green when the battery is fully charged.
Lean
Rich
See
Tuning Your TRX 3.3
Racing Engine
on page 25
for complete information on
adjusting the air/fuel mixture
and idle speed.
Factory Needle Settings
If your factory preset
carburetor adjustments have
been tampered with, use the
following settings:
• Set the high-speed needle to
4 turns out from closed.
• Set the low-speed needle so
the screw head (
red in Fig. A
)
is flush (even) with the end
of the slide (
yellow in Fig. A
).
Always use the factory
settings for initial starting.
Only use these settings when
the factory settings have
been lost.
Higher nitro requires a richer
fuel mixture. When running
33% fuel, richen your high
speed needle 3/4 turn if
previously running 20% nitro
and then re-tune the engine
for maximum performance.
Low Speed
Needle Adjustment
Fig. A
THE TRX 3.3 RACING ENGINE
2
3
1
2
