TRX.15 Carburetor settings

Article #50741


Note: From the factory,your carburetor has been preset to the following break-in specs. Do not readjust your carburetor settings unless you suspect that the settings have been changed or if you need to make adjustments for altitude (above 3000 ft).


The mixture screw controls how much fuel enters the engine. With the radio system on and the air filter removed, adjust the throttle trim knob on the transmitter until the throttle just closes against its stop. Now, turn the mixture screw clockwise, by hand, until it stops. (Do not tighten or the needle may be damaged). Now, turn the mixture screw out, counter-clockwise, 1 3/4 complete turns.

NOTE: If you live in higher altitudes (3000 feet or higher above sea level), it may be necessary for you to set your fuel mixture as lean as 1 1/4 turns out from closed. Make sure the engine runs rich during the break-in process. Call 1-888-TRAXXAS if you have questions about setting your fuel mixture.

The idle screw regulates the throttle opening to control the idle speed. The throttle opening at idle should be set as shown in the drawing. The opening should be 1 to 1 1/2 millimeters at the widest point in the opening. The idle speed may need to be readjusted after the engine is warm.


All final tuning adjustments must be made to the engine at its normal operating temperature after the engine has been broken-in. Click here for instructions on
Click here to see a short movie clip demonstrating
the sights and sounds of a lean engine.

Any of the above symptoms indicate that the fuel mixture is past maximum safe lean setting. Turn the mixture screw back out (counter-clockwise) the previous 15-degrees to reach the optimum fuel mixture setting. Turn the mixture screw out another 15-degrees for non-race applications. This will extend engine component life. This setting will vary slightly with each engine depending upon fuel brand, temperature, humidity, etc.


Now that the engine mixture is tuned, the idle speed may be set too high. If the model moves forward at idle, reset the idle speed by removing the air filter and adjusting the idle speed screw on the side of the carburetor. Turn the screw out (counter-clockwise) until the engine will idle consistently (without stalling) and the model will sit still without any brake being applied. If you are having to constantly blip the throttle to keep the engine from stalling, then the idle speed is set too low.

Your rating: None