Redcat Racing – How to Tune Up Your Redcat Racing Nitro Engine Part 2

Written by Jason Scott. Posted in Radio Control Cars & Trucks, RC Zone

redcat racing nitro engine

Before you read this article you may want to see how to tune up your redcat vehicle part 1

Let’s take a look at the effects of tuning on the high speed needle and low speed needle on the redcat racing volcano which is using an SH .18 3.0cc 2 stroke nitro engine with rotary carburetor. Before seeing the rotary carburetor, the air filter must first be removed. The rotary carburetor opens and closes by rotating the drum inside make sure that the carburetor opening get is 1mm or so. Use an idle speed screw in doing so.

This is to ensure that your Redcat Racing Vehicle will not run away on you!

1mm gap carburetor

A properly tuned Redcat Racing engine should be able to handle full rpm on at full throttle.

If you purposely enrich (max fuel to air) the High Speed needle,  you will see that it cannot take on full throttle. (The high speed needle or HSN controls air and fuel mixture for partial and full throttle.) The mixture would be consisting of more fuel and less air. If your HSN setting is too lean (too much air to not enough fuel), the engine might bulk or quit when you try to go to full throttle. If it doesn’t quit, it might bulk on full throttle, which is a very dangerous thing for your engine because when an engine overheats it gets damaged.

Now, let’s look at the effects of the Low Speed Needle (LSN) settings on the Redcat Racing engine. Certain precautions must be noted and practiced so as to avoid damage to your Redcat vehicle.

When the LSN is leaned out, you will see that the idle will change. When the LSN is closed (clockwise), you can hear the engine starving for fuel and begging for it. If it speeds up, your truck or buggy might take off by itself even if the carburetor opening gap is set to 1mm! This will give your Redcat Vehicle the tendency to overheat, which is clearly not good for the engine of your race car.

If you enrich the LSN by opening the needle (counter clockwise) You will see that the engine won’t start or the engine would quit as soon as we take the ignitor out. This means the LSN setting on your Redcat Racing Vehicle is too rich.

The Pinch test is the best way to check if you have the LSN properly set on your Redcat Vehicle or not.

Pinching the fuel line

This is done by pinching the fuel line and the engine should raise its rpm or speed for around 3-5 seconds and then it quits. This means that the LSN is properly set. If it quits too quickly, the LSN is too lean or when it quits too slowly, the LSN setting is too rich. If your LSN is too rich 0 to partial throttle, the engine will stutter to go from 0 to partial throttle or when it’s too lean,0 to partial throttle will fail to take place and the engine would quit, resulting to it speeding up immediately.

For Redcat Racing Parts and Hop Ups see our online store at

For more information on Redcat Racing Nitro Vehicle Set Up See Articles:

Setting Up Your Nitro Redcat Racing Vehicle

Redcat Racing Nitro Basics

How To Use a Redcat DSM Radio

How To Tune Up Your Redcat Nitro Engine

How To Tune Up Your Redcat Nitro Engine Part II

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Jason Scott

"They will Rue the Day They Gave Me Free Reign Over this Blog" Ha Ha Ha Ha Ha! (insert evil into laughter)

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