How to adjust idle on 4 stroke dirt bikes - fuel screw adjustment 

this guy should make videos on every thing he knows because he explains things so thourghly without 1 extraneous fact its literally the best how to video I have ever seen! Thanks for posting!

I’m 14 and only have a tiny bit of experience with my dirt bike and couldn’t figure it out. My dad has a lot of experience but none with Honda. Thanks again for helping me out

I’ve been struggling with my bike for a months to make it perfect this helped more than all other videos I watched🙏

This his such a good demo that I bookmarked into my tech how to folder, It's well choreographed, clear and concise. Thank you!

never adjusted a carburetor before - watched your video after rebuilding my sons old secondhand carb(after watching another video) , and now it runs PERFECT ! Thank you. Great video.

Finally someone who knows what he is talking about. Keep up the videos. The hot start trick on jetting help me so much. My bike runs like a beast now. And my air screw is at 1-7/8 out instead of 2.5 as set from honda. Much safer to run a little rich than lean. I'm totally amazed at his ability to explain carburetor. Help with my 2-stroke on another video also. Thanks again for being awesome.

@Dirt N Iron thank you so much for making these videos! I have owned my WR450F for only 3 weeks. Having never owned anything with a carburetor I ended up unscrewing the idle screw all the way out. Luckily I was able to take out the carb and re-screw the idle back in. Your videos have really helped me understand the carburetor and how to conduct maintenance on my bike.

My family has DRZ 125L that is having trouble idling. We've tried so many things but nothing was working.This video was so helpful!

Great video, he knows his stuff. I adjusted my yz250f just the way he explains. WOW, throttle response is amazing, what a difference from before.

Thank you for this video mate! It's very clear and easy to understand. Now have a job for my WR450 tomorrow!

I can’t think of the right words to describe how much this video helped me so I will just say thank you!

"stay motivated, see you later" only reason I sub. Staying motivated when doing any work my man love it.

Great explanation! I bought a non running yz426f and rebuilt the carb and it back fired like crazy! After taking direction from this video however, my bike is much happier and pulls fat wheelies now !

Thank you so much man, I just bought a yz250f and I thought I got screwed over on Craigslist because the bike was not running the way it should’ve been and a part of me was scared to ride it but this video fixed all of my problems and I just wanted to thank you for this detailed video🙏🏻 definitely subscribing because I’m sure there is even more to learn that could help me out.

Woah, this is what i'm looking for. Thank you!

I installed a R&D Racing Flex Jet in my Suzuki DRZ-400E and hung it off the metal feul inlet on the carburettor with a zip tie it is the best mod for on the go tuneability especially when going high and low altitudes i highly recommend this product to everybody just do it you won't regret it.

Thank you very much for taking the time to help everyone! Your an awesome person!!

Thank you. I've read about this process, but it didn't make sense until I watched this video.

BOOM! Glowing pipe and backfiring sorted! Thanks Rado!

I have the same bike with all these issues..... You explained this brilliantly, to the point where i know what i am doing! Lets see if it works though,,, wish me luck!!

Wow this is a really helpful video, got a 2008 wr250f recent practically brand new. I'll definitely be using these tips when tuning my carb 💯👌🏾

Great tip (near the end) on the hot start with little or no response, meaning maybe too lean. That was very helpful in getting a KLX450R carb dialed in with a little more fuel mix. Thanks! (Prior to viewing and tweaking, hot start worked for hot starts, but still backfiring on shifts and trailing throttle.)

Thank you very much for this informative video I have no experience when it comes to bike maintenance I just got my first bike crf450r it wouldn’t idle on its on after watching this video and following these steps I was able to get it up and running correctly it wouldnt keep idle because it needed these adjustments as they weren’t correct and hot start made no difference in the idle which was how I figured out it wasn’t jetted correct and I was able to fix it thanks to you

Very informative, I appreciate the help. I’m trying to tune my carb and this helped a bunch.

Great job on explaining this. Some where in one of his videos he mentions putting in , I’m assuming an in line fuel filter, but I never saw that. Has anyone seen that? I’m curious as to where he installed it. Was it a 90 degree or straight etc

Never watched such a simple and informative video top notch stuff man

I have an RPM gauge on my bike and it's recommended I have an idle around 1800 RPM. For this procedure approx how many RPM above 1800 should I aim for to begin? Thanks!

100% on the money, before watching this I was left perplexed thinking the worst case scenario. now I know exactly what im listening for and how to dial them in and the bike is 100% on the money cheers for the helpful upload

i think this is the 5th time i look at this video. always helps me. thanks

Wanted to say thanks for the video brother. I bought a new carburetor and I could not get it running right. I followed what you said , turned the screw all the way in and back it off a little. And it’s now running. Thanks.

Hey Rado, I’ve bought my first bike about a month ago. It was a project and it was the first time I rebuilt a motor. To make a long story short, I did this rebuild with only RU-vid tutorial videos. Now she’s up and running and she’s finally getting the love she deserves. The bike is a 2006 KX250F. I’m having, I guess you can call it a bogging issue at mid-high rpm in any gear. Where the bike feels sluggish, then at times she’ll die on me and I have to wait a few minutes before the bike will start. I can’t tell if it’s too rich or too lean. I tried to set my aftermarket fuel screw exactly to this video. However, my bike increases in rpm instead of dropping around 2 - 2 1/2 turns out. If this is correct l, it never fixed my problem. The bike pulls very hard during test runs but there’s something not right with the fuel system, any suggestions? I’ll be riding at 496’ ASL around 15-25 degrees Celsius (59-69 Fahrenheit) When I opened the carb up I found: 180 main jet 55 Leak Jet 40 Pilot Jet 68 Starter Jet Needle Jet: 2nd last clip on the top. Thank you for the excellent content, I watch all of your videos and I’ve learned so much. You motovated me to get my first bike since I was a kid and I can’t wait to get this baby on the trails. Love from Newfoundland, Canada.

This video was key to getting my 2001 WR250f to start with one kick...

This video saved me sooo much time. THANK YOU!!

Dude, this is an awesome video. I am having similar issues that you describe on my sons 2004 Yamaha wr250f. I am going to try all of these adjustments to see if it will clean up. thanks!

Lookin now at others reviews,, wish i saw this years ago!!!!! Thnk you!! Youre like the bike whisperer!!!

Had to subscribe to give a small help, thanks to this video i now know exactly how to properly set my air/fuel screw aswell as the Idle one! Thank you very much!

I keep coming back to this for tuning

Precisely my issue! Got it adjusted and running like a champ. 05 YZ450F. Thanks!

Shop manual says idle speed is 1700 rpm. Ridiculously high IMHP. Can't we make them tick over around 600? Great video. Watched it twice so far. Will look into the idle screw mod. Thanks

When I screw the air/fuel screw in all the way and bring the idle up, as I bring the air/fuel screw out the revs are going up, not down. Any suggestions? Bike is a 144cc 4 stroke 🤷‍♂️

thanks a bunch for making this! just got a 450 ktm smr and your videos have helped me lots to understand the FCR carb!

Problem is WR450F dirtbikes are now fuel injected. Does this still goes for the fuel injected? The muffler is getting red hot and people is telling me fuel or jetting is too rich making the muffler red hot. Thanks for the video.

Hello! Your videos have been helping me put together my 2013 YZ250F your a big help! tuning the carb it seems okay but I believe it’s not 100% correct because when I pull in the hot start it just boggs or the idle deteriorates even if the fuel screw is turned 3+ it doesn’t change the hot start idol it boggs, can you please give me some pointers on how to fix this or what is the cause? Thank you!

Amazing work! Keep up the good work. The video is very good and informative :)

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?

Hi, thanks for the info, One question, with the screw all in and the right pilot jet, the engine Will die? Because mine, with all the screw in, still run, but with more high RPM

the adjustment of fuel screw depends on the design or model of the carburetor, whether fuel screw is located before the slide or after the slide, if the fuel screw's location is same as the video, turning clockwise is getting leaner while counter clockwise is richer that's why rpm is going down when adjusting the fuel screw counter clockwise, on the other hand, when the fuel screw is located before the slide, turning clockwise is going richer, and turning counterclockwise is going leaner that's why in this design if you turn fuel screw counterclockwise the rpm goes up. You can directly observe this when you turn fuel screw counterclockwise it's either the rpm goes up(leaner) or the rpm goes down(richer-same as the video) hope this helps if you're struggling tuning your carburetor.

I haven’t rode my dirt bike for almost 2 years man I miss it

Legend brother...thank you so much. After doing all the free mods. This was key to fix the back firing

On point I just fixed my bike in like ten min was about to take it to the shop many thanks my guy🤘👍

Thx after 4 years i finally got it right

Great video I’m having real bad issues with my 2008 yz250f. Feels the power is getting robbed in every gear except 1st and 5th. Idle is high but tried adjusting the fuel maybe the idle screw is the key?

This guy is pretty good. Made it simple for me.

Perfectly explained! 10/10

got my first dirt bike last year only got to ride it now because it was sitting and we moved to a place where we can drive it daily and keen as to ride it

The most clear idle adjustment video I've seen.....

wooow thanks a lot man my idle was staying high sometimes and I would never have guessed it was the hotstart ! 👍🏻

I adjusted mine the way you described and it runs great at idle great throttle response and revs up with hot start but when I go to ride when holding in clutch to stop and down shift it dies any suggestions

Hey buddy is the fuel air knob the only adjustment on these? I have a 17 crf230f and I can't get it to stay idling and it's hard to start up and keep running. I can get it to start full choke but then when I lower it to half choke or no choke it dies out. This has been an ongoing problem for a while where I've got it running and Stay running but it's had trouble on cold starts and staying running. I took the fuel petcock off as it was running in reserve but not on on. So it was clogged when in on position so I cleared the clog but now I'm still having trouble. Now I think I killed my battery from starting it so much and not staying running 🤬🤬 Also my bike only has one black knob above my carb. There is a small adjustment screw at the bottom of the carb on the face of it, one that you would adjust with a flat head driver

Very useful and clear explanation! Does that procedure apply also for the Yama WR 450 F my2007?

Help, I did everything you suggested, however, when I turn my fuel/air screw OUT it actually does the opposite. It starts to increase RPM, not decrease. Any thoughts why this is? And when I try to rev the engine, it bogs down and dies. However, it runs GREAT with the choke on. Confused. Any help would be great. Thanks.

Nice Video, If I may I’ll add something else to do with WR 450 or any other Carby 4stroke. I personally don’t like the after market fuel adjustment screw, this is why. I keep the OEM screw , adjust as required , generally if your jets are right size and clean , you will end up about 2.5 to 3 turns out on mixture screw. It is tricky to adjust OEM screw, but not that hard use a tiny screw driver BIT Now once the bike is running right your happy with mixer screw setting , put a blob of grease in the mixer hole, behind head of screw , then stuff a tiny bit of rubber / sponge in the hole behind the grease. 2 reason, stops the screw coming loose .they do and can fall out, or change the mixer setting, and the mixer screws can and do leak past the thread , screwing your mixer ever so slightly also, if it falls out it will stop, 👍. After market screw vibrate loose also, put a rubber band on it also.

Ok. I have watched the 2 Stroke (Air Screw vid) and this one. Both awesome and very informative based on the sound and feel of the motor. My question is. I have a 4 Stroke. Kawasaki KlX 110 that utilizes an AIR Screw. So. Can I set it out 1.5 turns from closed then richen it up to the low rpm state or do i lean to highest rpm? Don’t want to go from only response. I Like the way you can get close by listening to rpms based off the screw manipulation (opening or closing).

Hi rado, rpm doesn’t stay up when I push hot start ,it raises for two seconds then goes down. Do you know why?? Thanks

Thanks my bike would not want to start today at all so i just kept turning the screw till it did kick start and then when i finnaly had it running i turned the screw until it sounded just right👌, i have only been riding for 2 weeks now.

What is the order of the spring o-ring and washer on the after market screw? Websites show it differently... 😅

Wow was I wrong !! I needed a 48 size pilot jet now my bike runs great. Yes I was a dope, At least I can admit it when I'm wrong.

Thanks for the video, what I was looking for.

You should do a video about float height it's the mostly commom problem on carbs

Praise Chapel Romania. Sector 5. Great video my man. God Bless

Man this video is awesome! Could not have come at a better time. Thanks a lot!

Sir, recently I had clean my bike engine head, after that, my bike didn't start in cool with out using choke and running clogged at least 1 km. What is the problem? Please reply.

Allot of very helpful info, thanks

What exactly do you mean at 3:38 "raise the rpm a little bit higher with the idle screw"? I think my idle screw is not adjusted well in the first place. So how do I know where the idle screw position (a little bit higher than normal as you say in the video) should be in order to continue with the procedure?

Im trying this Saturday. Also do you think if I have a really cheap battery it's causing me ignition problems? 1993 dr350s

This is good for 4 stroke motorcycle engine too?

Awesome vlog and Intel. Very clear guidance and details.Thanks heaps. Just subscribed. Get it

Will this stew really help or just mess up my carb

After years,,, my 450 is dialed in!!!!! Thnx

dude ur videos are so inndept and wheel teached i could watch u all day

DirtNiron, i can't understand this method because most mechanics talks about finding HIGHEST rpm between rich and lean fuel screw adjustment. You doing opposite (finding lowest RPM). Can you explain who is right and who is wrong ?

Shouldn't you set the idle mixture screw for highest idle speed, not lowest?

This video really helped me out thank you! Very easy to follow instructions - thank you sir!!

Dear sir. Thanks a lot for your explanation. I think now i understand what is going on on my bike

Does aftermarket exhaust cause lean mixture? I have to turned my pilot screw more than 2. I already go 1 size larger slow jet, I think 2 size larger will fix the issue. Is that normal to go 1 or more larger slow jet?

This video pulled me out of my WTF episode.

Awesome video great explanation!!!!!!

Vegas RoManiac stays up too late at night watching the Home Shopping Channel.

Such a great channel, keep up the great work 👍🏻

I hope this question get answered but I’m just curious, could you use the hot start as launch control

This is what I need to see I took my vento thriller racing 200 to a shop they said it's supposed to bog down on quick blips of the throttle 🤣it's normal but I'm the original owner and it was crisp when I bought it long story short I never went back bought a new carburetor and with this video I'm ripping again

very helpful explanations thankyou!!

Great video. What causes the idle to stay high when pulling in the clutch to stop?

Hey I always thought the hit start was the red knob beside the black Choke on the side of the carb? I have an 01 yz250f? Can you help me answer this question I've asked many other ppl, never with a definitive response

Hey man, thanks for the info....once you have it dialed in, is it possible that the plug shows signs of too rich/lean....or will this process ensure the plug reads as "sweet as"? Can you elaborate on hotter and colder plugs please

Can you please give me advice on my Tao Tao 125cc four stroke carb change n adjustment

hi rado, I have a 2001 honda trx400ex quad I just picked up. it ran good with the fuel screw pretty much all the way in, but the idle was way to low coz it wouldnt stay idling, I changed the idle screw and moved the airscrew out (regretting that now) do u have any suggestions to get it running?

Awesomeness, bought an 05 KTM EXC 250 yesterday with a huge flatspot after idle. Is the accelerator pump adjustable too?

Thank you this helped imstantly ,great video.

At the beginning you screw idle a little bit high can you please tell me approximately how much 2500 rpm...? Thanks Great video maybe it will help me. I will reply then)