34
The TRX 2.5 Racing Engine
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.
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.
Tuning the TRX 2.5 for Best Performance
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.
Before you begin tuning, the engine should be warmed up to its
normal operating temperature and running slightly rich. All final
tuning adjustments must be made to the engine at its normal
operating temperature.You can tell the engine is running rich
by noting any of the following:
Sluggish acceleration with blue smoke coming from
the exhaust.
There is unburned fuel spraying from the exhaust tip
Leaning the high-speed fuel mixture increases performance
High-Speed Fuel Mixture Adjustment
With the engine warm and running at a rich setting,gradually
lean the high-speed fuel mixture in 1/16 turn increments.Make
several high-speed passes with S-Maxx after each adjustment to
clear out the engine and note any change in performance.The
TRX 2.5 is extremely powerful. Remember to apply the throttle
gradually to prevent wheelies or loss of control.Continue this
procedure until there is no longer any performance
improvement.
If any one of the following conditions occurs, the fuel mixture
is already past the maximum safe lean setting:
1. There is no longer any performance improvement
2.
The engine begins to cut out at high speed
(Danger!)
3.
There is a sudden loss of power during acceleration
(Danger!)
4.
The engine begins to overheat.Symptoms of
overheating include:
Steam or smoke coming from the engine (not exhaust)
Hesitation or stalling during acceleration
Popping or clattering sound when decelerating
(detonation)
Fluctuating idle speed
Temperature measurement above
270° F
at the glow plug
Richen the fuel mixture to the optimum setting by richening the
high-speed needle at least 1/8 turn counterclockwise and retest.
This setting will extend engine component life.
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