How carb jetting works | Offroad Engineered 

How do we know if the engine is runnning rich or lean? what about a lotta rich or a little rich and vice versa?

If Spark plug is clear and white it is lean . If spark plug has carbon black carbon on top it means rich mixture.

This is the clearest explanation I have found for how carb jetting works! The graphics are a huge help. Thanks!

This is, by far, the best carb info video on RU-vid (based on my research). Thanks, it was very helpful. What an amazing piece of engineering.

Absolutely genius by having the graphics. In jet pilot School they use graphics similar to this to explain jet engine blows and the operational systems of the jet. The carburetor video is well above any class I've ever taken. Keep up the excellent work, good sir!!

for everyone who wants to know: a lean engine will be more silent and gives a slight delay at low throttle. so you pull throttle, and a second later your engine responds. a rich engine will have quick throttle response but gives bogging (on a 2stroke it is called 4stroking), so the engine makes a faster and louder sound, but the power decreases when its doing that.

Dude your video is one of the best that explains how a carb works.. You literally killed explanation... I don't know If I am going to rejet my carb, but your video really helped to fix my carb..

best carburetor video on the internet

Having the graphic to assist explaining how are carb works was very effective. This may be one the best carb videos online. Would love to see another related to float bowls and there method of operation. 👍good job.

Loved it, A good base line explanation without getting too technical. Keep up the good work.

Great video! Straight to the point and really cleared up the questions I’ve always had for proper carb tuning. Graphics helped a lot!! 👍 Thanks for sharing!!

You made carbs looks like a simple device XD Thanks a lot :)

Luis, thank you for continuously and consistently providing quality content. It is time to stock up on jet needles :-)

This is the most niche YT channel I've subscribed. I love your videos. And this is another great content. Keep on doing yours Steps to Podium, Luis. Cheers from Poland.

This really is a great video. All the info without overcomplicating things. Thanks.

Yet another brilliant video! Great work my man!

Best carb video I've seen on here, thank you, sir!

That makes everything much clearer. Thanks

You did a fantastic job on this video. Very well done

Mais um excelente video! Parabens e obrigado pela partilha!

Super easy explained and so clear after this video thx!

I’ve worked on carbs forever. This is a real good tool. I know to change things. So now I exactly what I’m looking at

This is by far the best video understanding the carburetor. Thank you so much I will be following you from this point on.

Oooh, I hadn't seen this one! Brilliant as always! I learned soooo much, man!

Another great video. I am surprised by some of the negative comments. I just recently got back into bikes and two strokes. You gave an excellent foundational video. You are correct in saying it is time to go get your hands dirty, and I am sure guys can go do additional homework on tuning, plug reading, other means of figuring out how to dial in the carb. Also, being able to take feedback from the machine is critical.

Excellent video! Thanks for sharing! 🙏

I think I just learned more about a motorcycle carburetor in 6 minutes than I have in the past 40 years. Thank you!!!

Excellent video with easy to understand graphics. Thanks for posting.

Good video. Really easy to digest too! Thank you for sharing your knowledge.

Excellent video with clear descriptions and explanations... Yes.. you video is worth 10,000 pictures.. Thanks..

Very helpful in visualizing and assessing my problem with adjusting my new nibbi carburetor. Thank you

Iam a factory tech and this video I have fwd to students thx u . 🎉cheers

Great video. Thanks for the quality explanation

Great examples and video and info!! I'm definitely a new sub!!

one of the finest videos ever on the subject.

I´m not a beginner but i tell you this is the best video on YT for jet adjustement. See i power up my little 50cc two stroke to 75cc and i´m preparing well my first start. So people may thing on the first start you have to be cautious with too much rpm, but thats not true. Throttle up a two stroke means lubrication and thats what the engine needs at the first start with new cylinder and piston. But if you start up lean it can bring catastrofic consequences. So this video gave me the tutorial i needed. I adjust first needel to warm up the engine. To warm up we apply certainly one to three quarter throttle, so for that the needle is responsable and has to be the first adjustement. When this is ok i go for the idle by adjudting the air screw and jetting if necessary. The main jet will be adjusted on a longer ride with fully open throttle. Ohhh man, i got a plan, lol. Thanks a lot, greetings from Spain.

Very well explained.

Best video on how carb. Works Thanks

Very informative! Thank you sir.

Great explanation, illustrations & summary

Mais um vez um excelente vídeo, com excelentes animações. Não esquecer também a afinação da boia 😉

Great video, thank you very much!

Great explanation! 💪

This video helped me so much thank you😊

Great video thanks for the easy explanatio ❤

Это первое видео где я смог проследить взаимосвязь между режимами, спасибо графикам. Я уже долгое время пытаюсь найти хорошую информацию по настройке карбюратора для своего VMAX 1200, все остальные видео представляет из себя в основном "бла бла бла". Спасибо большое. Если будет возможность хотелось бы видеть виддео подобного же плана, но уже с реальным мотоциклом и реальными настройками (желательно 4х цилиндровый). Что-бы можно было более четко проследить логику подбора. К сожалению не у всех есть под рукой стенд для точных измерений.

Very good video, helpful 👍

Excellent video! 👌

great video

Great video! Tks 🎉

Thanks.... Easy way to understand

Very good video

awesome video

Thanks for the explanation. Tuning the RZ500 is still a pain in the ass.

Hugely helpful. Thank you for sharing this knowledge.

Thank you Sir

You can adjust carburetor niddle up and down. It will give rich or lean mixture depend on niddle and fuel mixture screw. Niddle setting gives best acceleration response.

Show de vídeos muito bem explicado

Thank you

Excelente!

Excellent video and the graphics really helped clarify what was happening and when. Question: is there a practical way to test this without fully installing the carburetor into the boots? I suspect not.

Good video! Also a float level set too high will make engine run rich.

I didn't watch it but I'm sure it's going to be gold.

What a fantastic, clear video. Am new to this and looking to help iron out some running issues with 4stroke 50cc gy6 ped. Issues being slow to pull away from standing, can almost die. Also some bogging at full throttle. Also generally slow. First I'll just do a carb clean. I'll then see how it runs. Depending on how it runs.... Is the first thing to alter is the needle size? Or does it not matter, but only change one thing at once? Thanks!!

Como sempre, as animações são do melhor que podemos pedir! 👌 Varias marcas tem no manual uma tabela com recomendações conforme a altitude/temperatura a que andamos na mota. Bastante útil para ter um ponto de partida, pois por norma são sempre um pouco mais ricas, para salvaguardar o motor. Melhor trocar uma vela, que o pistão! 😂 Ja agora, na gasgas que tinhas, que setting usavas para hard enduro? É que a tabela da gasgas é para esquecer.... e melhor nem falar da agulha de origem!! Continuação de um bom trabalho! 👌💪

Very good 🇧🇷👍🏻

Best explanation 💯 Question: have a straight piped Honda shadow 1100 that hasn’t be rejeted and I’m in the process of it. How should I rejet it? In idle it’s to boggy and when I’m in mid rpm’s I have to give it more throttle

Great visual thank you!!!!! How about a O2 sensor for measuring air/fuel mixture as a tool?

Top top !

Gracias!

Great video thanks. Just a question if that's OK. When travelling down hill on my 2 stroke Beta Xtrainer 300 with the throttle fully closed I get a lot of surges, so much so I often pull the clutch in. What's the cause of this. Many thanks Chris

Muito bom 👌

Super Trooper 👌

Great video Luis, just one thing the needle jet is mounted into the jet block, not the slide ;-)

Legit exacly what I was looking for at 3am

Great tutorial ! I have been trying to tune my carb for awhile , 1985 XL 350 , installed a Mikuni carb and mid and top end , after some rejetting are doing well , my issue is with the zero to 1/4 throttle , when riding it fluctuates too much , constant variation up amd down , choppy i guess might be the term , thoughts ?

Top 👍

Great video! I assume that air temperature also affects how you jet your carburetor as well

Will help if i change the mainjet from 0.82 to 0.99 and the atomisor with more holes to mixt more air?

I have a 50cc 4-stroke scooter with a pz16 carb. Had a little trouble with idle, switched the stock 35 slow jet for a 38 and now it idles fine, and the mixture screw reacts like it should. It runs fine all the way from idle through almost full throttle. At full throttle it loses power. Doesn't backfire or die, just a a slight loss of power. If I back off just a little from wide open, it runs better. I'm thinking I need to swap the stock 75 main for a 78. Does that sound like a move in the right direction? Thanks for any info!

Great video. Would have been perfect if went through the air/fuel mixture.

I have installed bigger pilot jet and needle lowered to 2nd position but there is light sputtering apart from that performance is very good. So due to sputtering I lowered needle to 1st position and sputtering stoped but less power in middle throttle position.should I change the larger main jet to gain more power or the larger needle to be installed with the circlip positioned to 2nd or 3rd depending on the performance Thanks

Are both jets supposed to work at the same time? For a 2 bbl? Or is one a idle jet and the other a main jet.

My 4-stroke bike starts pretty good cold. Sometimes 1st kick. But when it warm, it's hard to start, and it starts most reliably with half choke. What does that sound like to you? I'm thinking maybe the main jet is a little to big, or a little too small?

Hey Thanks for the video 👍🏻 My bike seem to have a delay in dropping the rpm after I let go of the throttle while riding , Is that too lean or too rich mixture? It also seem to overheat a bit

My four stroke Yamaha 90 must be on quarter choke otherwise stalls. Would bigger jet hole help with that. Thanks for help

The bikes not picking up on low throttle fast enough what jet do I need to change bigger or smaller?

The number one reason customers came to my shop . A clogged pilot jet on a carbureted bike . First indicator ! If you need to partially run your choke once the bike starts and it won’t idle well with the choke off . Do that enough and you eventually foul your plugs . Know the first signs !

So ... On a car we have an 02 sensor or wideband O2 sensor to monitor its af mixture, HOW do you know how lean or rich it is on a motorcycle to know if you need a smaller or bigger jet or needle ??

Can you make a video explaining flooding and how to fix?

What about thickness on needle for hot weather? Hot and dry.

The way to set it is to look at the color of the spark plug after the motorbike engine is running... if it's wet or black it means it's wasteful, if it's dry it means it's economical.

If using an Amal concentric, the needle jet wears, probably on other brands too

Great video my bikes to lean on idle and when I start to ride it it bogs so does that mean just a bigger idle jet and bigger main jet ?👍😊

Ohh, that part about needle jet & needle combo was good. I have problem that I raised the needle a lot and my afr is still to lean in the mids. Does that confirm that I need new bigger needle jet and needle? I'm running zzr1100 carbs on bmw m10b18 engine so there is little info on tuning from scratch

in which part it should be decided that the engine has more power thanks

Hi Thanks for the video! I have a problem with a hanging idle. When i start the bike it just runs normal but when i give it a hand of throttle the rmp stays high and wont drop. When i pull the choke out and right after i put it back in it lowers down to the desired rpm. When i ride slow technical stuff and pull the clutch the rpm rises again and only drops when i let the clutch out. What do you think the problem is? i ride a crf250x

My 01 YZ250 will only bump start or push start, once it starts it sounds nice and crisp. Elevation here is about 2000 feet above sea level at least 100 degree heat. I will try leaning out my pilot jet from 175 to 165 and see what happens. What are your thoughts?

How do you determine if it’s too lean or too rich at each stage (idle, mid-throttle & full open)?

Honda XR400R done 4000km and was getting difficult to start Once started it would only run on half choke. So I bought a rebuild carb kit with all the needles and rubber rings. Hex Main Jet - #140 Slow Jet - #52 Jet Needle - D625 Fitment: Fit for Honda XR400R 1998-2004 Cleaned that carb like a new pin. Fitted the new parts. Paid attention to the original screw settings. Starts easily no choke. Open it up it dies. Put half choke on it just about let’s you open the throttle but doesn’t like it. Put full choke on and can open the throttle and drive about easily. What have I done wrong and what do I need to do?