4 PRO Tips To Optimize Your Go Kart Carburation (X30 and OKJ/OK)

By Alessio Lorandi, 2013 CIK-FIA World Champion, KF-Junior. Updated on 29 October 2026.

If you’re serious about getting your carburation perfect for your go kart….

…Then pay attention because this article is exactly what you’ve been looking for!

If you’re an X30 Junior, X30 Senior, OKJ or OK driver and you’re struggling to get your carburation right, then this guide is for you.

Why does carburation matter in karting?

The reason why we want to have the best carburation we can get is because that will allow us to have a higher performance overall from our go kart thus making us more competitive during the races.

If the carburation isn’t right, you’re losing horsepower. And that’s something you can learn to get right yourself.

What do too rich and too lean mean?

A good carburation is neither too lean, nor too rich.

It’s too rich when there is too MUCH fuel used for combustion and you see lots of smoke coming out of the exhaust.

It’s too lean when there is too LITTLE fuel pumped in the engine and that will oftentimes result in an engine seized due to a lack of lubrication.

Now, let’s get started and see what you can do to feel and tune the carburation accordingly.

How do you know if your carburation is too rich?

The first thing I can advise you to do is to feel the throttle response once you go on power in the exits.

If you feel that there is some slight delay between your throttle application and the actual throttle response, then it usually means your carburation is too rich.

You should contrast that by giving less fuel and then see how much it improves.

That is the most simple thing to notice once your carburation is too rich.

What does the engine sound tell you about carburation?

Okay so this is a little bit more complicated to feel and it usually takes a bit of time to get the feel for it.

It can be easily noticed by pro drivers but also for them it took quite a while to learn it.

What we’re talking about is feeling the engine sound on the straights.

What do you do if the engine sounds too lean?

In that case you would wanna give some extra fuel on the bottoms or you could cover the air box filter with one hand at the end of the straight.

By covering your air box filter you will automatically send more fuel to the engine which will make it slightly richer and reduce the chance of having your engine seized.

So to sum it up: if it’s not loud at all it might mean you’re too rich whereas if it’s louder than normal it means you’re too lean and you should make an adjustment.

What does a lean engine feel like just before it seizes?

You can kind of tell, just a few laps before seizing the engine, when your piston is about to give up. At the end of the straight it’s almost like shooting, that’s how I say it. You feel the engine is too lean and it’s giving you a signal: I’m about to give up, I’m about to break.

And if you’re really about to seize, there’s not much you can do. In a shifter kart, pull the clutch and come back into the pits.

That’s why your hearing is so important for the carburation. So many times it happened to me that I’ve noticed the engine sound shifting a bit, getting just a bit too loud, and that told me I needed to give it some extra fuel, either changing the carburation or by putting my hand down the straight by making it richer.

It saved my races a lot of times and for sure I wouldn’t have brought the kart back in the pits if it got too lean but I couldn’t hear the sound shift.

Can the exhaust temperature tell you if you’re too lean or too rich?

The third tip I have for you is to pay close attention to the exhaust temperature from your Mychron or Unipro.

You should both check the top Temperature and the Bottom temperature by looking at the Maximum and Minimum temperature, respectively.

When they’re higher than they should be, then it usually is too lean and you should give more fuel. Whereas if they’re lower, then it probably is too rich and you should try giving less fuel.

But higher or lower than what? There’s no one number for everyone. Say for instance your engine tuner has seen on the dyno that the bottom works best between 440 and 460 and the top between 620 and 640. Those are just numbers as an example. It depends on many aspects, mostly on the exhaust sensor you’re using. Your aim is to reproduce those same temperatures on race day, while the track conditions change.

Carburation stays guesswork until you can see what the engine is telling you. The kart EGT guide on PURPL covers what exhaust gas temperature actually means for jetting.

When should you check the exhaust temperature?

You should check the exhaust temperature both after the session via telemetry analysis and also during the session by checking at the Max temp on your Mychron at the end of the straight.

If for example you see that it keeps going above the range your tuner gave you, then you know that you’re too lean and you should take action to make it richer.

What happens when you cover the air filter at the end of the straight?

Finally, as we’ve already mentioned, you should try and cover the air box filter with one hand at the end of the straight and see what happens.

Before explaining it in detail, you need to know that when you apply this technique, the carburation will get momentarily richer since there will be more fuel going to the engine, thus reducing the chances of seizing the engine when you’re too lean for example.

How long should you cover the air filter?

You should do it for just 1 or 2 seconds, not more. It will be enough to understand, trust me.

Here are three possible scenarios that will happen:

• The first is that nothing changes and therefore your carburation is spot on.
• The second is that the kart will slow down, and that will mean that you’re too rich.
• The third scenario is that it actually makes you go even faster and pick up speed and that will mean you’re too lean and should therefore make it richer.

What can you do from the seat if the carburation is wrong?

You can’t come into the pits for a setup change halfway through a race. But you can adapt, and take the engine back in the window yourself. That’s where the driver makes the difference.

• If it was too rich at the start of the race, pick up the throttle a little earlier. That leans the engine out a bit.
• If it’s too lean, put your hand over the airbox down the straight. Less air for a fraction of time, and it gets richer.
• If you’ve got a membrane carburetor, you can “open” the carburation and give it some extra fuel.
• In the worst case, in the last few laps and with less pressure from behind, wait a tiny bit longer to go on the throttle. That sends more fuel in the engine, and it helps.

Nobody cares about your post race blames about your engine being too lean. So focus on the ways you can fix part of the problem with your driving, not on the problem.

Should you start a race on the rich side or the lean side?

It’s a choice, and you can’t have the best of both worlds. Especially with float carburetors, like in the 60 Mini and the shifters, where you can’t change the carburation by yourself from the seat like you can with a diaphragm carburetor. So you, or your engine tuner, have to decide before the start.

If you go towards the lean side, you’ll have more performance in the opening laps. The start procedure pumps in lots of fuel. And on the first laps the tyres are cold, you have less grip, so you wait longer on the throttle, and that pumps in even more fuel. The engine richens up by itself.

But then the laps go on and the grip comes. You naturally get on the throttle earlier, and the carburation gets leaner and leaner. In categories like OK and KZ2 you’re risking to seize the engine. So the last few laps will make you suffer more than the drivers who started richer.

If you start on the rich side, you’ll struggle more at the beginning. Tiny delays on the throttle, the first response feels quite “dirty”. Then it gets better lap by lap, and halfway through the race it’s just perfect. That’s when you’re faster than the drivers who started lean.

Same in practice. A rich carburation may need some laps to “clean” it before the response comes back.

Why do drivers lean out the carburation on the formation lap?

So you don’t have too much fuel for the start. Too much fuel gives you some delay on the throttle response, and you lose acceleration right when you need the jump. Most drivers do it, me included.

I tried to find the secret of Max Verstappen’s pace in the opening laps. Niente. Nada. What I saw is that he was tuning his carburation on the formation lap, in KF3 and KF2 with membrane carburetors, making it nice and lean on the bottom to get the best acceleration at the start. If you rewatch his race videos, you’ll see one hand on the steering and one hand on the carburetor for the final part of the formation lap.

The rest of the start is in kart race starts and the first lap.

How do rain and cold change your carburation?

You can’t run the same carburation between the wet and the dry. You need to lean the carburation out massively. Because every time you brake and you wait to go on the gas, the engine gets filled with fuel that doesn’t get burned, and it becomes rich.

Normally you lose performance in the mid range, but also in the bottom. You will feel like the response is more dirty. It’s delayed. It’s laggy.

So you need to have everything at hand to change jets. Or if it’s an X30, you can just close the carburation with the two screws, super easily. The rest of the rain setup is in wet kart setup and the wet line.

Cold is the opposite problem. If it gets very cold, your carburation is going to get very lean, and you have to adjust it. Otherwise the piston is the next thing that gives up.

Does the fuel change your jetting?

Yes. One of the things we’ve noticed is that when we run with a high octane fuel, we actually have to make the carburation a little bit leaner in the jets. The higher octane makes it a little bit more rich. With a lower octane fuel we do the opposite: we increase the jets to make it a little bit richer and compensate for that.

The oil mixture affects the carburation too. Normally that’s about 4 to 5 percent, depending on what your engine tuner wants. Too much lubrication and the carburation probably is not going to be perfect. Not enough and it will actually be worse, and with something like 1 or 2 percent there’s a high chance of seizing. More in karting fuel and oil basics.

Who should change the jets, you or your engine tuner?

Even though tuners set a “baseline” carburation, it should be the driver responsible to adjust it (or ask to adjust it) based on the track conditions and feedback.

The tuner does the tuning at the workshop. At the track he does the setup: more bottom, more top. But before he understands what to do, you’ve got to give him clear directions on what you want.

If you keep telling him to go in the wrong direction, you’re going to upset him and you’re going to lose some credibility. I saw many drivers giving wrong feedback, and I still see them. And unfortunately the engine tuner stops listening to that kind of driver. More on that in the driver and mechanic relationship.

What maintenance keeps your carburation right?

Clean your airbox. Every once in a while you’ll get some dirt inside, and you don’t want stones, grass or pieces of sand going through the carburetor into the engine. That may cost you a lot of lap time, a race, or even seize the engine.

Clean your fuel tank and the fuel filters that are connected to the pump too. And replace the spark plug when you feel like it may be cutting off.

Check the axle and the rear rims as well. If they’re bent, the vibration makes the carburation inconsistent, and it can damage the crankshaft too.

And if you’re just doing it for fun, for casual hobby driving, with a carburation that is quite rich, you won’t have to change the piston that often. Way easier to maintain. The rest is in karting maintenance basics for beginners.

What do drivers ask most about kart carburation?

How do you know if your kart carburation is too rich?

You feel a slight delay between your throttle application and the actual throttle response, and the engine is not so loud on the straights. Give it less fuel and see how much it improves.

How do you know if your kart engine is running too lean?

The engine is louder than usual on the straights, and just before seizing it’s almost like shooting at the end of the straight. Give it more fuel, or cover the airbox with one hand at the end of the straight.

Should you run a leaner carburation in the wet?

Yes, and by a lot. Every time you brake and wait for the gas, the engine fills with fuel that doesn’t get burned, so the dry carburation ends up too rich in the wet.

Does high octane fuel need different jets?

Yes. With a high octane fuel we make the carburation a little bit leaner in the jets, and with a lower octane fuel we increase the jets to make it a little bit richer.

How long should you cover the air filter to test the carburation?

Just 1 or 2 seconds, not more. If nothing changes your carburation is spot on, if the kart slows down you’re too rich, and if it picks up speed you’re too lean.

Put these things into practice and let me know how it’s going.

I hope these 4 tips to help your go kart carburation were helpful and I look forward to hear from you directly.

Related guides: Karting Fuel & Oil Basics Explained Simply | Karting Maintenance Basics For Beginners | How to Optimize Your Kart’s Gear Ratio for Different Tracks