Factory Carburetor Settings for TRX 2.5, 2.5R and 3.3

Article #50983

TRX 2.5, TRX 2.5R, & TRX 3.3 Racing Engine
Factory Break-In (default) Carburetor Settings:


High-Speed needle

TRX 2.5, TRX 2.5R, and TRX 3.3 Racing Engines:
A good starting point for the high-speed needle
is 4 turns out (counter-clockwise) from closed.


Low-Speed Needle

Notice the thin darker gray area between the low speed needle and the throttle arm. This is actually the other end of the slide valve from inside the carburetor. The low-speed needle is threaded into the slide valve and is set flush (even) with the edge of the slide valve.

Note: This is a good base setting. Adjustments may
need to be made to the low-speed needle for best
performance in your running conditions.


Idle Stop Screw Idle Gap
The idle stop screw controls the idle speed by preventing the carburetor slide from closing completely. Turn right (clockwise) to increase idle, and left (counter-clockwise) to decrease idle. A good starting point for the slide valve to stop at idle is a 0.7mm-1.0mm gap.

The carburetor is preset at the factory for break-in. The base setting should be right to start and run the engine through the break-in process. However, if you are having trouble getting the engine started or keeping it running, then you may need to readjust the fuel mixture to compensate for factors such as temperature, humidity, and altitude (air density). It is a good idea to bring the tuning card that was attached to the fuel tank with you.


Tuning Card
Download the card (PDF) under the instructions category.
Tuning Card Front
(click for larger view)
Tuning Card Back
(click for larger view)

This is a very informative card and will be extremely valuable, especially to those of you that are new to nitro R/C. You can tear the card at the perforation and place it in your wallet or pit box.

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