TRX 2.5R • 24
3.
There is a sudden loss of power during acceleration
(Danger!)
4.
The engine begins to overheat. Symptoms of overheating include:
If any of the above conditions occcur, 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.
Low-Speed Fuel Mixture Adjustment
The low-speed mixture is always set after the high-speed needle is correctly adjusted.
Set the low-speed mixture using the following pinch test.
1.
Once the engine is warm, do several high-speed runs to confirm that the high-speed needle
is set correctly.
2.
Bring the vehicle in and pinch closed the fuel line going into the carburetor. The engine
should run for 2-3 seconds, speed up, and then die.
3.
If the engine runs longer than 3 seconds, then lean the low-speed needle 1/16 turn,
make several more high-speed runs, and retest.
4.
If the engine dies immediately without speeding up, then richen the low-speed needle 1/8
turn, make several more high-speed runs, and retest.
When the low-speed needle is set correctly, the engine’s throttle response should be very quick.
Idle Speed Adjustment
Once the high and low-speed mixtures have been set, reduce the idle speed to the minimum
reliable idle speed. Remember, this adjustment should be made while the engine is running at
normal operating temperature.
1.
Turn the throttle trim on the transmitter so that the brakes are applied. This ensures that
the throttle slide is resting against the idle adjustment screw.
TUNING THE TRX 2.5R
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.
• Fluctuating idle speed
• Hesitation or stalling during acceleration
• Steam or smoke coming from the engine
(not exhaust)
• Popping or clattering sound when
decelerating (detonation)
• Temperature measurement above 270° F
at the glow plug
When adjusting the low-
speed fuel mixture, it is
very important to make
several high-speed runs
with your model between
adjustments to clear out
any excess fuel. Perform
the pinch test immediately
after. If the engine is
allowed to idle for a long
period of time, it could
“load up” with fuel and
give you an inaccurate
measurement from your
pinch test.
