The BEST Way To Fine Tune Idle Mixture Screws For Your Carburetor 

I have spent 20+ hours trying to get my dirt bike to run, trying to learn carbs. This video is a godsend and now my bike is running right!

Cody, you’re not talking too much. The person that would make such a comment has both an at attention span of one minute and a motorcycle that runs like crap. Keep up the good work.

Thanks for the explanation of hanging and high idle slowly returning to normal being a lean condition, and low idle creeping back to normal being a rich condition. These types of tips bring it back to the basics and make it much easier to understand. Much appreciated.

I am 74 years old and have doing it for 55 years. It works exactly like that for cars as well. We call it the sweet spot.❤🎉

Holy crap I'm 67 years old and I finally learned how to tune a freaking mikuni. Thank you very much you don't talk too much you talk just right and tons of information. Again thank you very much I'm a subscriber now

I don’t think you talk to much. I find your descriptions extremely helpful. One of the reasons why I watch your videos. The explanations are great and so helpful!

Yo dude, not able to go to a motorbike mechanic so these videos are bloody unreal, subscribed ! Thanks again

ppl really complain about u talking to much. these are how to vids, i hate how to vids where u don't get enough information. ppl just like to complain

Great advice, clear for those who just want to tinker at home! One note however; As a bike mechanic I've always been with the understanding that once you've found that sweet spot where the engine idles at it's highest, we should go clockwise 1/8 - 1/4 of a turn to make the mixture is ever so slightly rich. The rpm will still drop back great to idle (you wont notice), and it's a general rule of thumb that a teeny bit too much fuel is better than a teeny bit too much air. It keeps everything a little cooler. Engines always run most efficiently when running slightly lean (also in terms of power output). The down side of this of course is that it produces a more risky, hotter combustion. We don't need maximum power efficiency at Idle, and for this reason it's better to always adjust that 1/8-1/4 turn in. Keep up the good work!

Couple of things. Not bad. However, do not blip the throttle. When you blip the throttle, slide goes up feeding fuel, and then drops cutting off air. It results in a rich mixture. The best way to adjust the pilot/low speed circuit is to stabilize the idle/warm engine, set the idle speed, and then start turning the mixture screw either in or out. (It doesn't matter which) if the idle drops, you're going the wrong way. If the idle goes up, reset your idle screw to bring the idle back down and repeat. You want to get to the point where turning the mix screw one way or the other either makes it worse or does nothing at all. That's your sweet spot. Much harder with a multi-cylinder motor. As for your comment about air screws being more sensitive to adjustment, it's likely because, if the carb has an air screw, it's probably either an old street bike or something that the EPA didn't require a fine adjustment. Because of this, the taper is fatter and produces a more pronounced change with the turn. The EPA carbs had a long slim taper. (Really easy to screw them up if you turn them in too hard so be careful) They require a lot more turns to equal what something like a 1/4 turn on a non-EPA carb would take. You also mentioned compression but left out valves. A tight valve, bad seat/valve is going to throw things off so, before adjusting a carb, make sure the valves have been adjusted and the engine run. Lastly, in the 80s Yamaha made dealers purchase Allen exhaust gas analyzers. You'd install fittings in each exhaust and get a reading from a single cylinder. None of my co-workers used it but I got familiar with it. Yamaha specs were out to lunch, but I figured a great way to use it. I received lots of favorable comments from my customers when they got their bikes back. Probably the biggest take away I got from using it was, after the carbs were set on the machine, I'd check turns out from seated. These were the thin taper screws, but they would range anywhere from 1 1/2 to as far out as 3 1/2 turns! (2 1/2 was baseline) It all depended on the seat in the carb and how badly the factory had wound the screws in. (I'd actually find some that were completely seated!)

As a retired industrial engineer and maintenance manager I have worked with hundreds of people over my 45 year career. The key to teaching someone ANYTHING related to mechanics or industrial automation or most any other field, is to not only teach them what to do and how to do it, the most important thing to teach them is the WHY you do it! Teaching them the theory of how anything is supposed to work helps them to understand the WHY! Without the theory behind what they are doing they are just memorizing a few basic steps ie when I see this I do that. You sir are very good at teaching the theory of operation along with the what and the how. Keep it up!!

Good info here. I have been using a ColorTune see-through spark plug from Gunson to set the idle mixture....by watching the color of fuel burning in the cylinder. Yellow glow is too rich, white is too lean, good deep blue is the ideal mixture.

As a retired mechanic (who still rides) I think this is an excellent video. I have worked on everything from motorcycles (mostly kawis) to automotive to heavy truck /heavy equipment and that was a great description on carb operation and idle tuning. Happy to subscribe to your channel and look forward to viewing other carb vids. Congrats.

I always did the highest rpm at idle and it has usually worked for me. Warm it up, then set a reasonable rpm for idle then fiddle slightly with the needle until you get the highest rpm possible.

All of your info is accurate, if i ever had to go past 2.5 turns out on the fuel screw though id always go to a larger pilot then start over to prevent the chance of the screw vibrating out over time. I personally dont feel like its got enough spring tension to hold the fuel screw in long term past 2.5 turns out.

I've always struggled with adjusting the air, but you just explained it in 15 minutes. Love your videos!

My first experience with small engines is a Zircon 150cc go kart. It was given to me because it didnt run. Without this video it still would not be running. This video was a huge help

I've worked at a motorcycle/ATV repair shop for 17 years and this is the best video I have seen that explains the process of tuning in the air/fuel mixture on a carbureted engine... you have to listen to the engine and make small adjustments and give the engine time to respond to your adjustments and until you find the sweet spot..... keep up the work good bro 😎👍

Great video, very well explained. Fantastic for the generations who didn't grow up with carbs. This will help to keep our muched loved machines used and loved for generations to come.

This was totally helpful. I am troubleshooting a DR650 carb. Based on your video, the carb was running rich. I got the carb dialed in now. Thank You! 🏍️✔️

Dude i have this video saved to to keep my memory fresh

Glad you made this, I have a friend who's having some trouble understanding carbs so i sent this his way

I just set the idle speed screw a bit fast, keep adjusting the idle mixture until the engine is at its fastest then richen the idle mixture by 1/4 turn and readjust the idle speed back to normal. However, on my 2stroke bike, I set it lean and leave it there. Not bothered by a hanging idle and it prevents the engine being fluffy from oiling up a bit when running slowly in woods.

Best carb tuning video ever!!

Don't listen to folks saying you talk too much, how stupid. We are here to listen to you talk. Near the end you seem to have set the screw to get the highest idle rather than using the technique the video is about. Thanks for all your video, great stuff.

First off, i love the fact you “talk to much” i have learnt more from you, than for ANYONE on youtube (proud to call myself an MD member) This vid explained so so so much!! Keep them coming 😊 they are AWESOME!

You definitely do not talk too much, I would literally pay for this information I mean you explain it so well, better than most people. Thanks a lot brother!

What i learnt from watching a fella tune his hemi 6 was u can buy a device called a colour tune which lets u see the colour of the spark cournel as the engine is running. Seems a great visual way to adjust air and fuel for optimum performance. Thanks for your video . Talking through your points is good

Cody your detailed description is perfect for me, ive listened to so many & still have to pause play pause play whilst im working on my bike. I was starting to think ive got a problem until i watched one of your videos on carb tuning & it was perfect, so thank you great work...

Dude screw those guys who say that you talk too much. The more you explain it the better my understanding of it. A big thank you for helping people who don;t know how to get a carb set up and tuned correctly. There are always going to be that faction of people who feed off of negativity and haven;t leqarned the biggest lesson in life. Just ignor them. They are not worth listening to.

You are looking for the highest idle with the mixture screw, which allows the slide to be adjusted to the most closed position which will reduce run on etc. The highest idle is the most efficient air fuel mix poss, hence why it idles the highest with the correct mix. If the screw ends up in to far or out to far to gain that highest idle then it is a guide to know which way to change the pilot jet to suit.

First time I ever understood how to actually do this. I also love the fact that you don't care what type or brand of motorcycle the viewer is riding and instead make everyone feel welcome. You have my sub to the channel, now I'm off to find a video of your on how to clean a carb properly, as that's where I'm currently at with my 1988 Yamaha YZ125. Thank you! :)

You dont talk too much. Your speech is always on topic, and to the point. Id rather have someone "talk too much" but explain it clearly, than someone "talk a little bit first" about crap that has nothing to do with the topic.

Well done for helping home mechanics. Young bikers are often poor and cant afford a mechanic especially at KTM, BMW and Harley main dealers

Perfect! 👌 Very well said, very clear and with practical example, brilliant.

Your explanation of the lean and rich conditions of the how the engine operates was fantastic. Never had it explained that way to me and then backing it up with actual examples just really solidified it for me. Thank you so much!

Whoever thinks this is too much talking is a person that impatiently thinks and listens too little. I am in process of rebuilding and tuning a fleet of snowmobile carburetors and this is great information!

So I'm a noob and was trying to tune my 1990 Suzuki fa50 to the service repair specs and it just wasn't working! It would run but I could just tell it wasn't right. The way you explained how to hear what the engine is doing as far as being lean or rich was an aha eureka moment for me. I went straight to the tool box the moment I pulled the bike into the garage after work and had it running better than it probably has for 20 years. The bike sat for 18 years before I bought it for 300 bucks. Thank you so much I will never forget this lesson for as long as I live. 🤙✊🖖😎🫡🐐

Just to let you know that the idle mixture screw on a British Amal carburettor is on what you would call the “post-fuel” side of the carb but it is an air screw and weakens the mixture when you screw it out! Sorry to throw a spanner in the works, what you say probably holds true for Japanese carbs and others but not for the Amal!

I've been working on carbonated engines (controlled fuel leak) for 60 years. I was predicting every move you made. Great video.

I’ve watched your other videos that include mixture adjustments, glad to see you bring it back to light. In the past I never knew how it was supposed to be done. Thank you for sharing!

Thanks for this lesson. Just put a new carb on my bike. This will help me get it perfect.

You might have just saved me from losing my bike man. I was about to give up on it fr. I haven't tried these screws but I'm just as new to riding as I am to carbs. I'm learning, though and you've taught me a lot in just this video alone and given me some hope.

Your video could not have come at a better time. Tuning my rebuilt carb on my CM400E today. Thank you so much!!

Would be interesting (for those of us who like to nerd out) for you to take a wideband o2 sensor and see where the mixture sweet spot ends up being on a gauge after you tune by ear as shown here. I’m guessing this method would produce mixtures around 12.5-13.0:1 air fuel ratio for pump gas.

Exactly the information I currently need. I love learning new things. Thank you.

watched your short about the air screw vs fuel screw and this just sealed the deal im dialing in the 73 at3 this weekend for sure! thanks for making things simple for a simple guy!

Hi Cody Greetings from NZ, I have slowly learned how to rebuild and sync my carburetors but haven't yet mastered the fuel mixture adjustments. Thank you for sharing your knowledge with me, I appreciate what you do.

Keep on talking, that's the best way we can learn anything. Great timing, I am just doing a single cylinder carb clean on my bike and this was the second video of yours I have got notice on. I'll be researching your videos to check what you have there...Thanks from an older biker who forgets too much. All the best from Australia.

Thank you for this great knowledge! I’ve got a dual carb which I was terrified to mess around with but your videos give me confidence to work on my bike!

Bro I have been searching for this for sooo long… thank you sooo much for posting

Your explanation simplifies what was a mystery to me for years. Took 2 minutes to set my bike up and it runs awesome now! Thank you Cody.

Very well explained procedure, then emphasized with a well presented actual example of the procedure. I'll have to begin watching more of your videos. Very impressed! I am getting ready to begin some restorations on several bikes I've collected thru the years. This type of information will probably be really useful. Thanks so much for presenting your videos!

Oh my goodness. Thank you. I have been have an issue with my 79 kz750 twin. Turns out I have the air mixture screw. Cant wait to get this dialed in!

Dude you rock! Best carb video I’ve ever seen!

Nice video and good explanations. Although as a generale rule you can tell what you are adjusting (air/fuel) depending on the position of the screw, there are exceptions. For example my Honda 50cc Joker which has an air adjusting screw but positioned on the 'fuel' side of the carburetor. What is worth mentioning is that a 100% way to determine what kind of adjusment you have is the type of screw tip you have. If you have a conic shaped end of the screw it is an air adjustment screw. If it ends with a very thin needle shape then it is fuel that your are adjusting.

Hi love your channel, have you ever tried welding wideband bungs and testing carbs AFR? I have AEM x sensor and two welded bungs to tune the carbs in all RPMS and i have found that my old Suzuki is way more sensitive for lean mix than rich. When you are leaner than 13 idle drops clearly, above 13,5 it start to pop. Between 13 and 12.5 rpms rise but not by much and to hear a significant drop in rpms you have to flood it bellow 11.

I work on CBX's and find that synchronization of the carbs needs to be performed first. If one carb has the throttle blade open just a little more than the other 5, it basically fights for supremacy and causes a hanging idle. 2 or more out of sync is worse. That's why an accurate (as possible) bench sync is important. I also enlarge the idle jets from #35 to #38 to compensate for the loss of BTU's in today's fuels in addition to being designed lean to pass emissions. Your video is very informative.

Wow, I have learned a lot from this video. Doing a carb cleaning right now and wanted to make adjustments to the air/fuel mixture screw and now I know what to hear for. Thank you!

Hey Cody, thanks for your video and tips. Though you picked an easy one by working on a bike that only has one carburator. This technique is pretty hard to apply when working on a 4 or 6 cylinders engine. After years of trying this I finally came to the conclusion that the only (easy) way to fine tune the idle mixture screws is to use a colortune where you can see the color of the mixture when exploding in the cylinder.

Hi I'm a barber and I can tell you brush your beard too much! Leave it alone only brush it with boar brush after shower! Friendly tip😁

I have struggled with this aspect of carb tuning for a long time. No one has ever explained the theory as you did. Simple steps to remember, hanging idle and drop being lean and the drop below idle too rich. Awesome, beautiful explanation very nicely done. My 95 Ducati SS and 74 Honda 360 are very happy. Thanks sir.

Bro you've just helped me with my new bike and the new carburetor I put on it. I had absolutely no knowledge of how to tune it and your videos saved me. THANK YOU I am so happy to hear my first bike run like a champ and I'm learning so much about bikes I'm glad I bought this cheap beginner bike to learn with.

Hey bro this is the information I’ve been searching many years you finally gave everybody the cheat code thank you this is gonna work miracles on my go kart

The audio was fine

So good - thanks Cody! Just re-set the mixture of the Dellortos on my '75 Moto Guzzi. They were very lean as I had set them prior (per "conventional wisdom"), and I had all the symptoms you described. Now it warms quicker, idles lower, drops from a blip faster, and no flubby delivery from 2K to 4K rpm. Easy and fast to do too. Awesome!

Such a simple yet effective method. Alongside your jetting for pod filters video, I'm finally on the right track to getting my bike running right. I was so far off but this technique let's me know that quickly and easily.

Wow am 62 years old and I did my carburetor on my ATC three wheeler thanks I followed your video how to clean and how to adjust it and I did it yes 👍 thank you so much 👍👍👍

This has been the most helpful video I have viewed so far about personal motorcycle maintenance. Thank you

The biggest mistake I see, on older bike epically, is when people don't check the intake manifolds and chase their tail trying to tune carbs. Alway spray water at the intake rubbers before you touch any screws air leaks will cause high Idle, as you spray water the idle will drop. Excellent video you made son. This works on every carburetor ever made on any motor. You want the highest idle with the lowest slide setting you can get with that back to idle quick. It's a lot of trial and error. No 2 carbs act the same so the book is just a rough starting point. If you live on a mountain or by the sea everything changes.

I’ve been working old bikes for decades and just when I thought I’ve seen everything I guess I haven’t, thanks for the amazing information on this. The main thing I’ve learned about carbs is that to listen to your bike it’s what I tell all my friends. Believe me when you listen to her, it pays off in the end.

Best carb video hands down !! Great training piece for us novices to watch and understand carb concepts from a seasoned expert. There’s huge satisfaction in becoming more self reliant / self sufficient. Many thx !!!

Thanks for this video. I was trying to tune a new scooter carburetor and had it ever so close but not exactly set right. Your advise on listening for the difference finally allowed me to get this carburetor spot on. Thanks!

Brother you a LEGEND!! I've been screwing around with a bike and almost bought a new carb...and agent service wasn't any better. My Yamaha BWS 100 scooter has never been healthier, even since new 👍Appreciate you! 👋

Love your attitude and willingness to help us out with taking care of our motorcycles.

excellent video, i love it, ive just turned 18 and i have my dad's 26 yr old hero-honda splendor and i've been adjusting that screw without knowing anything, i used it to get different power and economy and also changed to a leaner mixture in winters without knowing, never touched the fuel screw, now imma fiddle with it

I learned SO much from this video! I'm pretty new to motorcycles and obviously no mechanic explained anything to me. It's so gratifying to now understand how these parts work! Thanks so much!

bro! damn. a lot of mechanics RN is solely dependent on manual's instructions like 2 and half turn, 2 and a quart without checking on how carb really sound based on AFR. they forgot the "feeling" thanks bro!

I use this method all the time back in the day when I started on motor with a carburetor works very well by listening at feeling the Motors 45 years easy

Thank you so much for the video. I'm a woman who works on her own motorcycle and I'm never awesome at tuning the carb so this helped a lot. I just put a whole new exhaust system on so I need my I might have to alter some things with the carb

I do not think you talk too much! Enjoy watching you explain things I seem to understand. (great job man) Thanks

Idle drop method from Honda. Adjust idle mix for highest rpm, then turn richer until idle speed drops 50 rpm. I have found this method produces a goodle idle quality and aids off idle performance, now tune the rest of the carb and enjoy the ride. 1971 f7 Kawasaki, 76 TS250 JDM Suzuki, 1981 XR500R european, 1984 1/2 Harley FXRT 95" custom, 1984 Harley XR1000, 2017 HRC Africa Twin DCT

Really good much-needed tutorial video. Thanks Cody. 🤠Greets from Australia (200,000 miles circa 1962 - 1976, then 2-3 yrs about 16 years later on)

okay I just had a little 22 scooter and I have watched so many videos I changed out my carburetor went with a bigger car never done any of this before in my life and I just watched RU-vid figured out how to do it but I watched so many videos and none of them exactly tell you how to do the the air fuel mixture your video I followed exactly and it's cranked up every time it idles perfect and it runs great thank you so much for your videos that you do.

Thank you, your a really good teacher ! I just got a 1982 kawasaki 440 and I love it !

Great explanation! Pretty much how I do my Amal’s on my 76 Bonneville. I’m gonna double check them again listening closer to how they come back to idle, thanks man!

I've always tuned for highest idle and then back off about a quarter of a turn... but I'm super stoked to try your technique. Thanks

Thank you. This really helped a lot. I work on a lot of small cheap carburetors that don't necessarily do what you think they would. With this information it made it a lot easier to figure out what was happening since most come without any idea of what they are and if air or fuel screw. Again thank you for making it a little easier.

And on small carbs like on a chainsaw, weedeater, where 2 mixture screws are right beside each other. The one closest to the engine is the high speed mixture. The other is the low/ idle mixture.

Thank you for taking the time to make these videos to help others. Well done!

Thanks i put new exhaust on and had lean issues good to see someone explain attention to detail well explained

This is the most informational video I could find on carberators, Thank you

Bro thank you!!! Other say you talk a lot but boy it helps tremendously for us folks that are just learning how to tune bikes. I have a mini bike carburetor issues. Trailmaster storm 200 Upgraded my air intake and jet then the carburetor started to leak but it’s the stock carburetor and after watching your video I’m feeling better and more confident on what to look and listen for!! Appreciate you!! ✊🏽

Thanks so much,I found this the best explanation I have found on this topic, Just spent the morning working on my enfeild bullet 500 Mikcarb VM28, after a full strip and clean I found out why I couldn’t get it to idle properly,someone had screwed in the mix screw too far and it had broken through the casting,they then had to screw it home just to get it to kind of run,,,,with a tad of what looks like glue blocking it up a bit….needless to say I won’t be going back to that mechanic again…..swapped it with another carb I had ,no problem now thanks to your fantastic advice,and reading the informative comments ! .many thanks from NZ. subscribed .

Alright what the heck? BJ over at Brick House Builds got me going enough about older bikes to actually drive my Oh so sketchy trailer with my 1995 Ranger 800 miles there and 800 miles back. (George Washington Bridge, broken trailer, lucky to be alive yada yada yada). But now the dusty but all original 95' 750 night hawk is in my shop next to all the snowblowers (carburetors on tecumseh 8 horse engines ~ 4 of them.). So now ~ Alas, I will let BJ know that you have my attention now. He will understand. Thank you, keep talking man!. 〰✨👍✨〰

I've worked on hundreds of carbs but always learning how to do things with less guess work! Love your explaination and demonstration. I am better having watched your video. Cheers!

Great info. I have my Armstrong MT500 to set up tomorrow. It's taking a while to settle back to tick-over, so now I know it's lean. I know what I'm doing now. Thank you.

Thank you so much, probably the best carb tuning video I've watched so far! really appreciate you sharing your knowledge and experience with us

Just walked in from first start after carb rebuild and engine swap. Great timing for finding this. Couple things seemed backward, lean makes hang high for instance but awesome video. Will be exploring channel. Thank you.

excelent tip, my dad taught me this as a 15 year old, great video