Radio Control Car Action

Bubble trouble?

Bubble trouble?

Mertes, Doug

Bubble Trouble?

First, I love your magazine. About six weeks ago, I bought a Traxxas Nitro Sport. It is my first gas-powered R/C car, and I ran into a problem with it pretty quickly. It runs well for about two minutes, and then the engine dies. I know why it won’t run, but I don’t know how to fix it. I think it dies because there are air bubbles in the fuel line. Would a fuel filter do the trick? Also, when I try to start it again, the fuel won’t go into the engine; it reaches the carb and then shoots back to the gas tank. Do I have to replace any expensive parts? I hope not, because I’m just iz years old and low on funds!


Littleton, CO

The condition you describe (stalling after warmup) indicates that the fuel mixture is too lean (not enough fuel for the amount of air that is going into the engine). Nitro engines require a proper air/fuel mixture to get the best performance. In cases where the mixture is way off, the engine may never start, or it will stall after running for a few minutes.

When the engine warms up, it’s not able to draw as much air into it, and that reduces fuel intake. When not enough fuel goes into the engine, it will run poorly at higher speeds and may eventually stall. The real problem when there isn’t enough fuel is that there also isn’t enough lubricant, and that can cause severe engine damage!

The TRX-is engine included in the Nitro Sport features an easy-to-adjust carb that has only one mixture needle (more sophisticated engines have two mixture needles). Turn this mixture needle (the black “knob” at the top of the post where the fuel goes into the carburetor) about 1/2 to 3/4 turn counterclockwise. The engine may run poorly when it’s cold, but when it warms up, it should be closer to the ideal mixture for an engine that’s at running temperature (or possibly too rich).

Before you start your engine, prime the carb to make sure that fuel is in the fuel line and the carb; pump the primer bulb on the fuel tank until fuel reaches the carb, then give it one more pump to get fuel into the engine.

Seven important points to remember when running a nitro engine

1. Always adjust the fuel mixture when the engine is at running temperature.

2. Always adjust the mixture from rich to lean.

3. If you’re unsure whether the mixture is rich or lean, make sure it’s rich by slowly turning the needle counterclockwise until the engine barely runs.

4. When you are sure the engine is running rich, begin to lean the mixture (turn the mixture-needle knob clockwise) only 1/8 turn at a time, and run the engine about one minute between adjustments.

5. When you reach a mixture setting that provides the best engine performance, turn the needle back about 1/8 turn for a little extra “cushion.”

6. The fuel mixture always needs adjustment. An ideal mixture setting when the outside temperature is So degrees is entirely different from when it’s 6o degrees.

7. Before messing with any of the above, make sure your fuel lines and fuel tank are in good shape (no tears or cracks) and that they are properly connected.

Copyright Air Age Publishing Mar 1999

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