LeapFrog Nitro 4-Tec 3.3TM all-wheel-drive 4809 - Manual (Page 29)

Nitro 4-Tec 3.3 • 29
The TRX 3.3 Racing Engine
When tuning for
performance, watch closely
to notice when there is no
longer any increase in speed
or power when the
high-speed mixture is lean.
If you lean the high-speed
mixture to the point that the
engine cuts-out, hesitates,
or stalls, you are well into
the danger zone and engine
damage is likely. Richen the
high-speed needle 1/4 turn
and retune.
For your convenience, the
low-speed needle has a
positive stop that prevents
it from being over tightened
and damaging the needle
and seat. This also provides
an easy way to gauge how
many turns out from closed
the low-speed needle
adjustment is set to.
Winter Break-in Tips
During the break-in process, the piston and sleeve wear into each other to
form a precise fit. The engine needs to heat up to a temperature around 200
to 215 degrees to allow the piston and sleeve to achieve this fit properly. A
precise fit between these two components is critical for proper compression,
and optimum performance. If the engine runs too cold during break-in, the
piston and sleeve will not expand to their appropriate sizes for break-in, and
this can lead to premature wear of these components. This wear may not
become apparent until after winter has past, and the engine is operated
under warmer running conditions.
Warm the engine to approximately room temperature by removing
all fuel and storing the vehicle inside at room temperature until just
before starting the engine. An extremely cold engine can become
difficult to start.
After the engine is running, it is important to keep the temperature of
the engine up around 200 to 215 degrees during break-in. In weather
below 45 degrees, the TRX 3.3 Racing Engine will tend to run at lower
temperatures between 160 to 180 degrees (when tuned at proper break-
in mixture settings). This is too cool for break-in. Do not lean the fuel
mixture to increase engine temperature! This will also decrease
lubrication and cause your piston/sleeve to wear prematurely.
Wrap the cooling head with a paper towel,
clean rag or sock to help keep the engine
running around the recommended 200 to 215
break-in temp. If too much heat is contained,
the engine can actually run too hot. Make sure
that you monitor the engine's temp closely for
the first couple of tanks until you get the right
amount of cover for the cooling head. This will,
of course, depend on your current weather conditions. Adjusting the
cover up and down, exposing more or fewer cooling fins, is a convenient
way to regulate engine temps.
For owners that do not have access to a temperature probe, a drop of
water on the cooling head (around the glow plug area) should slowly
sizzle for approximately 6 to 8 seconds around 200 to 210 degrees. If the
water sizzles for only a few seconds, then it is likely that it is over 220
degrees, and needs to cool down. If the water takes a long time or does
not evaporate at all, then the engine is too cool.
We do not recommend that you operate your engine below 35 degrees
Fahrenheit. If you insist on running your vehicle below 35 degrees, be
aware that nitro engines may be very difficult to start and tune at
extremely cold temperatures. Also, at temperatures below freezing, nitro
fuel can actually begin to gel up, and this can be harmful to the engine.
Follow the remaining break-in procedures as outlined in this Owners
Manual. This, along with the steps listed above, will ensure a good break-in
for your new nitro engine, and provide many hours of enjoyment.
Tuning Your TRX 3.3 Racing Engine
The engine’s performance
depends on the fuel mixture.
Turn the mixture needles
clockwise to lean the fuel
mixture and counterclockwise
to richen it. Leaning the fuel
mixture will increase engine
power up to the engine’s
mechanical limits.
Never run
the engine too lean (not
enough fuel flow). Never
lean the engine until it
begins to cut-out or stall.
Leaning the engine beyond
the safe allowable limits will
result in poor performance
and almost certain engine
damage. Indications of an
overly lean mixture include:
Cutting out or sudden loss of power during acceleration.
Overheating (temperature beyond 270° F at the glow plug).
Little or no blue smoke coming from the exhaust.
If any of these conditions are present, stop immediately and richen the
high speed mixture 1/4 turn. The engine will probably be slightly rich at
that setting and you can then retune for performance. Always tune for
performance by starting rich and moving leaner toward the ideal setting.
Never try to tune from the lean side. There should always be a light
stream of blue smoke coming from the exhaust.