Adjust the air fuel screw until you get the highest idle. Should be between 1 and 3 turns out from all the way in. Then ride it and adjust the screw in 1/8 increments until you get the best throttle response. Then set the idle speed screw. If the air screw is best less than 1 turn out you need a richer pilot jet. If best over 3 turns out you need a leaner pilot. After you set this then you can check your needle and main. Cheers

2 turns to the left and 2 turns to the right. Got it, thanks man!

BTW you should do this with the engine hot

It's good to have your bike idle just enough to where it doesn't want to die. But folks, the main thing is. Two strokes aren't meant to sit and idle like a four stroke! They like to be wide open! Don't let your two stroke idle for too long.

Thanks for the help my 2000 yz125 was idling to low and this video helped me fix it in 5 minutes with the proper tools

Suppose to tighten the nut with a wrench while you use the Philips head to hold the screw in place. Tighting with a socket probably moved the screw....

It helps to have the bike warmed up using 5-10 mins of short on and off riding before you touch the idle so the bike is warm because what you will find is the bike will iddle nice when it hasnt been warm properly then five minutes down the road when its warm, itll rev quite alot higher than it did when you were adjusting it, but thank you this video did help me out on my Yam Yam too

Generally with popular bikes you turn clockwise to raise idle and anti-clockwise to decrease... but there is A MIXTURE SCREW THAT IS IMPORTANT... Firstly set the idle adjuster so that the bike is at lowest rpm without stalling. Now to adjust the mixture screw - find another little screw that just goes into the carb. and doesn't hold anything on etc. it should be flat-head screwdriver, have the bike off and turn it in until it seats, turn it out 1.5 turns (1 turn is 360 degrees of the screw), start the bike and turn the mixture screw anti-clockwise until the revs get to the highest point (when adjusting any of these screws only move them a little bit at a time, then wait 3-5secs), if it has more than 3 turns from seated then you either need a richer or leaner pilot jet... if your mixture screw was at the back of the carb. (near the air-filter) that means it was an Air screw, if it was at the front near the engine it was a Fuel screw. Let's say your mixture screw had to be more than 3 turns out to get it to idle highest, that means if it was the Air screw go leaner on the pilot jet, if it was the Fuel screw go richer. A bigger number on the pilot jet means richer. Only go up or down 1 size at a time and once the new jet is installed, repeat the process I just explained. NOTE: When adjusting the mixture it was just telling us about the pilot jet, we WERE NOT trying to adjust idle at all... the reason you need to know about the pilot jet is because that could be what is causing your bike to idle rough... so check that first. If the mixture screw is less than 3 turns from seated to make it idle highest... then your pilot is correct, so go ahead and leave the mixture screw right where the idle was highest and fine tune with the idle adjuster. ______ -- 2 stroke motocross bikes do idle smoothly but aren't designed to idle for more than about 1:30mins (some oil the plug quicker than others), it's the owner's choice of tuning that makes it idle or not.. tuning for more performance can sometimes mean the bike won't idle smoothly, especially if there are serious engine modifications. But if it just has a pipe and reeds etc. you should be able to get it to idle well. _______ -- 4 stroke -- All this is the same on a 4 stroke carb. except they can idle for longer periods, typically you don't want to idle a 4 stroke motocross bike for more than 4mins though as it gets too hot, it needs air going over the radiators to keep it at a normal temperature.

Thank you for making this video! My '01 YZ125 was kept bogging down if I started it cold with no choke. The idle made the difference!

You sir are a lifesaver.

I freakin love you bro! I saved up my whole life to get my yz125 and It wasn't idling and I was freaking out! This solved it!! THANK YOU!!!

Nice bike, and thanks for breaking it down into steps

One word: Manual. Helps a lot. Taking stuff apart to see how it works helps a lot too. Preciate the video though.

wow thanks bro i have the same exactly idle problem.. mine has gotten better but at one point i had to constantly bump start it because it would shut off during riding

It wouldn't be a bad idea to make sure you're float adjustment is to spec first. And I like to warm the bike up first, before I do any pilot, and idle adjustments . A lot of things to consider when tuning your carb. Check your spark plug after running it at w.o.t , it will tell you how she is running just by the color of the insulator under the electrode. Just some friendly advice . Sweet bike btw

Service manual is your friend. Yamaha happens to make very good manuals and this is all in there, including adjustment of the air screw.

a word of advise when turning up the idle speed get your engine running and hold the throttle at the target idle speed and screw the screw in till you meet the slide, else you end up with the problem i just had bike revs sticking and cant get a reliable idle speed because you drilled a shiny divot into your throttle slide with the rev set screw, open throttle screw in a tad release throttle and allow the slide to come to rest on the screw until desired idle is achieved, ive just had to dremel mine to smooth out a divot that was causing hanging revs or cutting out and now it idles reliably

good ole' Loogle, thanks for the video.

The more you turn the screw in the more you push the carberatour throttle shaft up,the same as when u turn the throttle the throttle shaft will come up letting more gas and air in

Nice bike man, have same yz in garage :) not much idle problem i hear. when i bought the bike it idle same as yours and then cleaned and oiled filter, cleand carb, reeds, decarbonized all exhoust system and and after i was like.. damn that bike can rip my arms off one day :D

What u were turning is called the air screw. To adjust it. U turn all the way to the right. Then go by a half turn each time till the idles good

thank you soooo much!!! so helpful!

Thanks for the video...it really help me out with adjusting my idle on my yz125. But it still tries to bog in first gear.

Thanks this helped me a lot

Thanks my guyyyyy this helped alot.

nice bike and thanks for doing this video i did it and it worked

Same problem with my bike thanks for help yo

That wouldve cost like 20 bux for a shop to do, now everyone heres turning air fuel screws whichever way they feel. Im gonna open me a shop doing rebuilds cus theres about 4000 of em coming soon lol

Thanks my bike kept dying but this helped

see my yz ticks over when I first start her up but when she gets warn she cuts out be that's for this video I try it when I get home. If you put more stuff on KZfaq that no else has plz do Il like to learn more about my yz 125 xx thank you. nice bike !!

right = closing the airway left = opening the airway if your bike jumps forward when you put it into gear, it means the clutch plates are warn out. Or you need to adjust your clutch

Box wrench doesn't fit in there and I do use a socket wrench but I had to use an adapter that kind of looked like a screw driver. Plus box wrenches strip alot easier.

We have the same petrol cap but I have a yz 85 and my petrol cap is gold instead of the blue colour you have

hey. left is lean and increases rpms. right is rich and decreases them. just letting you know

It always helps when u have a buddy

i was looking at this video, and then i decided to check my bike too, i adjusted that screw and now it idles perfect. (still have to kick it harder than normal)

Thank you mate! Appreciated. Having the same issue with my brand new 2021 yz125

on my 125 i had to use a box end because when you go to tighten up the nut the little screw turn with the nut

Thank you for this video. Got my yz125 idling wonderfully now.

Your bike is very clean. Good video and nice bike

thanks! great help!

Nice Graphics where did u get them?

Seems you have it pretty down pat heres a couple of tips: when you adjusting your idle screw blip the throttle (sit on the bike) because almost every time you move the screw tighter then blip the throttle it will rev a little higher.. you may also want ot adjust your idle mixture screw also when you get around to that (can do a video if you wish)

my dirtbike doesnt idle. i have to keep reving it to keep it running. is there anyway you can tell me how tyo fix it

Back your ideal out till your bike shuts off and leave it never let a 2 stroke idle ever it burns your rings quickly just start it with some throttle warm her up a bit and go

thanks man really hepled\

oh dude also check your spark plug cuz mine had the same exact problem then after i washed it it wouldn't even start so i called a friend he said change it and there you go my baby purrs like a cat!! Lon Live yzs gotta love em

I did change my spark plug but thanks man.

i had a 2001 yz250 once and it would idle good like that but then when you leave it idling for a bit it would drop down and be so low that the whole bike would shake but rarly stalled

Thanks. I know, i need a manual!

Thanks ,Rob

N-STYLE. I have an 05'. Not sure if they have them for your bike though.

Please tell me where you can find those graphics, and what kind they are... I have a 2001 yz 125 and I cant find any that I like haha, it'd be greatly appreciated. They're sick graphics. Also Good tutorial.

Hey I'm a newbie and I was wondering on some tips My old man got me a Honda Cr 125 2 stroke 03 model second hand and I tried to kick start it (spark plug brand new) and it just doesn't want to start Me and my mates tried to push start it and it didn't go either we tried to start it in second gear got it started but it sounded really terrible and just died on us could it be the carb?

hello i have a problem! my bike run out of fuel and now after i clean carb and put a new faange it runs on idle but when i give gaz she goes like " Boo gum booo gum !! lol i dont know what else to do! if i put iton first she goes down and wont start with the kickstart only by pushing it i manage to turn her on again! MAYBE some mechanic thing? ? ty

Wow this video help me so much , what way did you turn it again?

Dirt bikes are supposed to rev low if doesn't get reved a few times do u every see riders like my self but on a quad rev there bikes some times to keep running some times im not saying ur wrong all the way but im half right and u half right to thanks man

also a good tip when setting the idle is the position of the venturi. ***with the carb off the bike. your float level NEEDS to be correct before any of this 1. take the idle screw and with the venturi raised up turn the screw so the taper is all the way in. 2. drop the venturi back down so it sits on the idle screw and back the screw out until you see the venturi stop. then i adjust it so its not too high and not too low. when you look at the venturi from the exhaust side you should see a TINY bit of space between the front of the venturi and the exhaust port on the carb. 3. while you're down in there take out the pilot and main jet and give them a good cleaning. 4. take your idle air screw and back it out 1.5-2 turns. 5. start it up and adjust the idle air screw until it idles strong 6. then adjust your idle screw until it idles to your liking. the whole point is the venturi needs to be set properly while the carb is off the bike. if you set the proper height, theres no way your bike wont fire up instantly. carburetors can be very tricky to dial in, especially for beginners and something as simple as the incorrect float height will cause a machine with great compression and spark to run incorrectly.

I understand that racing bikes don't idle well. My ktm 85 2013 idles like a dream in neutral bur as soon as I click it in gear it drops dead. I have to rev before I click into gear otherwise it stalls out-what could I do?

I am seeing that many of you are having problems with your idling. This video is absolutely great for the last step but is missing out some key points that need to be covered before idle speed is changed. I have a 2003 cr125 and will be making a video tomorrow at some point that covers the key points before you complete this step. If any of you are still having a problem with your idle and are interested then just pop over to my chanel in the next day or so and I will walk you through it. :)

Will this work for a trial bike??

my yz125 wont idle when its warmed up. why is this? or is this normal?

so im not the only one who runs a renthal bar and pro taper grips. I have to adjust the idle on mine because its too high

my friend dillon roach has the same sticker kit on his yz250f

So is this not good for it?

they have tons of monster yz125 graphics excactly like those on ebay for 50 bucks for every year model

The reason it wasnt starting first kick sometimes was because theyre not made to start up and shut off all the time

Thank you!

just a question i have a 2 stroke kx 125 Kawasaki im wondering if your suppost to use your throttle in small burst like bam bam bam i used to hold it open all the time and im pretty sure thats what made my top end blow and not knowing what to maintenance on the bike i just need to know for sure tho thanks

Same problem thanks

I've got the mikuni VM carb

the way you adjusted it to be OK idling at a stop is not going to keep the engine alive if you break quickly or go down a hill. needs to be higher rpm.

That is not an idle adjustment screw. You are messing with the air/fuel mixture screw. The "idle adjustment" screw is just the throttle screw on top of the carb. You adjust that which makes it like your throttle is being slightly opened.

i have a question my 2000 yz125 has a really looks kickstarter and it slides down on the pipe, how can i fix this

Does that idle sound close to perfect before he messed with it? I started on a 96 rm80, yz 80s, yz125s, that's exactly how we had idle. Barely able to keep itself running. If your hand isn't on the throttle turn it off. They aren't supposed to idle like a trail Enduro roach does parked in the woods

All that does it lock my throttle In place, please help... my air screw will not fix my idle and I’ve installed the factory jets idk what else to do.

thanks a bunch

hi i have the same graphics kit on my yz125 2001

no shit lol its called a idle screw.

Hold throttle lightly and then turn it

2 strokes don't like to idle they just aren't that way. Always give it gas

2 strokes are meant to be at high rpm range , it's a race bike !!

Why do you want it to idle.

My 2stroke yz85 idles fine but after a couple laps it wont idle when i stop it just cuts out?but starts back up fine an continues running until i stop again Is that pretty normal lol im new as to dirtbikes

Do you know what size nut is for the idle adjustment?

All the way in and 2 full turns out

What Is the point of jetting and when is it necessary?

thanks

Thanks

Looking for a tip. I just got a 2020 YZ 125 and it just did this weird thing where it sputtered out like the fuel switch was turned off. I was running well, fuel on, no choke, then started to bog when throttled higher, then 2 min later, it just ran deal. won't turn over even with choke on. do I have to adjust something on a new one?

My yz125 when you start it or ride it it's really quite it's got an fmf turbine core 2 silencer and stock head pipe I rebuilt the bike to freshen up and it also takes awhile to catch up when going like late reaction could it be just not playing with clutch more or reving high enough or carb problem?? Or I have heard it could be reeds

Wow I realized I have a keihin carb mines different

Good cid

Does anyone know if it’s suppose to idle lower than normal after you rev it

Oh, gotcha

What happens if u do it too much?

Nice

@jbreezyburr , I had same problem , just clean out the carb and blow out the jets, I did it an mines runnin healthy as a hourse

Question all 2 stroke's have a button to cut it off ?

By going clockwise you'd be restricting fuel flow even more wouldn't you?