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!

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

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 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!

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!)

I've been jetting carbs since BEFORE there was a DYNOJET... You my man are the first guy i've seen that knows what he is doing! Besides me of course...LOL.... Great video. I loved jetting back in a day... Now I have moved on...

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.

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.

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!

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.

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...

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

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! 🏍️✔️

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!

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.

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

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.

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!

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.