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Them’s the Brakes [Tech Center]

Them’s the Brakes [Tech Center]

I have a nitro truck and the engine runs great but shuts down every time I stop. It fires right back up with no problem, but it’s really frustrating. How do I keep it running?

The problem here is the idle setting on your engine’s carburetor.  e carburetor’s idle screw sets how much the slide valve remains open when the throttle is at neutral. With the engine off , remove the air filter and look into the carburetor opening as you apply throttle—you’ll see the valve open. Now apply the brake, and watch the valve close. Even under full brake, the carburetor should remain slightly open, usually about 1.5mm. If it closes too much (or completely), the engine won’t get any fuel/air mixture and will shut down. Use the carburetor’s idle screw to set the minimum opening. Once your engine is warmed up, fine-tune the idle speed with the screw so that it’s fast enough to keep the engine running but not so fast that the clutch engages.

Nitro Engine Tuning

The idle screw is located in front of or behind the carburetor and easy to access with a small flatblade screwdriver.  The screw is a stop that sets the minimum opening for the slide valve.

Nitro Engine Tuning

Set the idle so that the carburetor remains open about 1.5mm, even when the brakes are applied.

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Updated: February 3, 2017 — 10:30 AM

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