How-to: Reset your Carburettor settings to Factory-Spec

Is your petrol-powered large-scale RC car not running right? Have you messed with the carburettor settings, or do you just want to get the settings back to a factory baseline? Then this is the blog for you!

Or to watch this blog in video form instead, click here!

The air/fuel mixture that is burned in the engine is controlled by the carburettor, and is adjusted with these two needles. They are labelled with a little L and H, for low speed and high speed.

Winding these in and out changes the air/fuel ratio, and if they are set wrong, the engine won’t run right and likely won’t even start.

If the needles are wound in, the mix will be leaner, meaning more air, less fuel. This will result in higher temps and potential rapid damage. Winding the needles out will result in a richer mix, and too much fuel will just make the engine sluggish, easily flooded and foul spark plugs. These are common factory baseline specs for most engines sized between 23cc – 30.5cc. Where possible, always follow the specified carby settings in your included user manual. These settings might not be an absolute perfect tune for every carby and engine out there – for that, you’d have to consult your engines user manual further and do a bit of trial and error. This is a common safe starting point for most engines to get your car up and running, and one of the first steps in diagnosing an engine that won’t start.

To reset their positions, you’ll just need a small-ish flathead screwdriver.

This is one of very few occasions where I’m not going to use an electric screwdriver. Sorry buddy, next time.

To get your carby back to a factory baseline tune, follow these steps.

Firstly, we want to firmly wind the needles in. Be careful not to over tighten as this can damage the needles. You aren’t tightening a screw here, so go gently - you’ll be able to feel when the needle is all the way in.

Now, wind the low speed needle out 1 and a quarter turns, like this.

I like to measure this out in steps, unwind 180, 180 & 90 degrees.

Next, wind the high speed needle out 1 and a half turns.

Unwind 180, 180 & 180 degrees

That’s it! You’ve either returned your carby to a common baseline or to the manufactures specified specs.

Thanks for reading, go and enjoy your large scale beast!