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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.
15
26 • T-MAXX
THE TRX 2.5 RACING ENGINE
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°F 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°F during break-in. In weather
below 45°F, the TRX 2.5 Racing Engine will tend to run at lower
temperatures between 160 to 180°F (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°F 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) can be
used to estimate the engine's temperature. The drop of water should
slowly sizzle for approximately 6 to 8 seconds if the engine is around
200 to 210°F. If the water sizzles for only a few seconds, then it is likely
that it is over 220°F, 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°F. If
you insist on running your vehicle below 35°F, 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 Owner's
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 2.5 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 so
far that 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.
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