Idle mixture adjustment (air OR fuel screw adjustment) Carburetor

[@thejunkman]

2023 UPDATE: If you are looking for "Chinese" or Honda clone engine information for tuning go here > www.thejunkmanadv.com/clone.html Also, this has caused some confusion over the years PLEASE READ: 2:20 this is an edited shot, 2 turns is just an example for this demonstration, your results may vary. A turn is defined by 360 degrees

[@clydecaguiat1754]

I stumble upon your video and it was great. I am having a hard time getting the rusty brown burn on my sparkplug even though I tuned my 150cc bike. Any recommendations? right now I am using a 28mm racing carb called Nibbi 28mm Supersport with 110 Main jet and 35 Slow jet, needle clip is set to 3rd notch and my sparkplug burns it rich. Hope you can help me out.

[@thejunkman]

Check out my other carburetor videos (links in the description). You still need to lean your mixture more.

[@thejunkman]

👋💡 2:20 this is an edited shot, 2 turns is just an example for this demonstration, your results may vary. A turn is defined by 360 degrees

[@benjibanks7894]

Thank you. My dumbass was counting by clicks. Huge difference.

[@jasonshourds7130]

Thank you sir.......ATV runs fantastic now.

[@gavinmcvey8177]

Cheers mate mine revs now without wanting to die it's a yx140z stomp thanks for the info on this cheers from scotland😎😎😎🇬🇧

[@tedtheturbot]

it doesnt take that long to turn a screw 720 degrees, why edit one of the most important parts of the video?

[@thejunkman]

@@tedtheturbot When I filmed this video over 10 years ago (it was originally uploaded on a different site, then here on KZbin) if I recall correctly I had some audio problems and only had one other take to use and the hands didn't match up with the audio. The visual really isn't the most important part, because 2 turns is just an example of where to start. The most important pat is the CONCEPTS presented here. The correct setting or starting point is determined by the manufacturer and listed in the service manual which those can range from 1-3 turns. That said I have and am continuing to produce more videos that try to address the concepts broadly enough to apply to most every motorcycle or situation. When in doubt, consult your service manual, it has the exact information for that exact bike.

[@TrentMRobertson]

Thanks for providing the simplest, most informative carb adjustment video on KZbin.

[@thejunkman]

If this video helped you out, consider giving a "THANKS" ❤ To help fund more videos like this!

[@JRMAIN]

Thks bro

[@thejunkman]

I am glad you learned something and got your machine running like you want. This is why I make videos.

[@amjadustad4359]

Carbater,is,name,four,sand,me

[@thejunkman]

Head on over to my website (link in the description) check out the comments section as this question gets asked a lot and I have answers over there, plus more videos that may help OR ask you question there and I can possibly help diagnose your problem. You can comment as a guest without having to register.

[@gerryhost8014]

I swear you worded this better then anyone ive ever heard

[@grand372]

Ditto

[@noelone5139]

This is the best way put I’ve seen on KZbin. I’ve seen at least 10 different videos. This should be at the top of suggestions

[@thejunkman]

Well share it around and maybe that will help it to the top! Thanks for watching.

[@crazycarpes]

For me its a total new way to set the idle !!! Thanks man! It works great on my carb!

[@thejunkman]

Please ask your question on my website, you will get better and faster help there. These new KZbin comments suck and I don't like them. thejunkmanadv.com KZbin has thoroughly mess up the comment system as I cannot respond to anyone's comments, at least right now. So if you have a question or comment you need to post it on my website for me to respond to it.

[@emilymazo9697]

Paul Turner

[@thejunkman]

That shouldn't be? Should be able to just put in a name (anything) and an email. KZbin did revamp comments a little so they don't suck as bad, but there is more info on my website to help you with jetting if that is what you need.

[@grasshopper2492]

thejunkman how do you adjust the fuel it on 2003 polaris trailboss 330.cant get under carb with screw driver

[@daniellepotts375]

So glad I found this video... Thank you so much for your time to new comers of the pit bike sport. I just bought a new SSR 160TR pit bike. It came with a generic manual that is so old it does not even match the pics of the parts. I believe It had a Minuki 26mm carb. From your video I relized it has an air screw adjustment. My problem is, at Half throttle is boggs down and can get out of its own way. I have to gingerly ease the throttle on and nurse it to get the bike running strong again. I followed your video and found that the air screw was set at 4 turns out. So I used your method of finding the sweet spot and it is about three and 1/2 turns out from full seat. I did not look at the needle jet or an other things since the bike is brand new. PLEASE PLEASE PLEASE give me some advice.. Again, I have read your spec sheets as well as your videos but I am stuck.. The dealer said I just need to choke it and clutch it.. which I think is BS.. Please respond.. Thank you- Jeff

[@yungae9453]

Danielle potts I have the exact same problem and I can’t figure out what it is. Have you figured it out?

[@joelangrehr6184]

@@yungae9453 New carb, check your jets and float

[@trendog7673]

This is the far most understandable video because he says how much turns he does Very nice and it helped a lot thanks

[@thejunkman]

Wait, the turns of the screw are just a baseline. Your actual setting may be different. Just keep that in mind.

[@thejunkman]

Ahhh, the magic of editing my friend. This has been brought up numerous times. Notice the crossfade indicating a jump ahead in time.

[@rexmatthews5174]

thank you! this "opposite" concept has created confusion in the past but your discription helps.

[@GreatBritishBeans]

Very well explained! gained a subscriber!

[@thejunkman]

I don't use KZbin as much anymore since the G+ switch, check out my website www.thejunkmanadv.com for waaay more videos like this and others, plus pictures! Check it out.

[@GreatBritishBeans]

Thanks mate!

[@mdsoto3893]

thejunkman hi I have questions my moped running but lose power

[@thejunkman]

+Teresa guzman ok, need more info

[@mdsoto3893]

thejunkman it running but when I speed up it loses power but when I doing slow is running fine! I'm not sure 🤔 what is the problem!

[@thejunkman]

@ROBOTNINJA500 Thanks for watching! Like my facebook page for more tips and tricks like this.

[@Tatorhead1234]

but you only turned the screw half a turn not 2 turns

[@ericmartinez4435]

Hunter Simmons That was just half huh, I was so confused

[@thejunkman]

Read the annotations. It is an edited shot, notice my thumb changes positions. 2 turns is just a baseline if you don't know the factory starting point. Te actual setting will vary from machine to machine and geographical location. 2 turns is irrelevant. Its the concept that is important in this video. That is made clear throughout the video and especially at the end.

[@the5general1]

that was half a turn !! for sure

[@matthewnichols8004]

A turn is actually a 1/4 full circle. Anytime someone says x turns that means x quarter turns duh

[@eduardosamora9360]

Hunter Cinnamons how you count turns i don't understand

[@chandrakantindapurkar8738]

Most essential information provided for those who is interested in to adj their carburettors at their place,the difference between air and fuel screw is nicely and simple word explanation given by you sir I am very much thankful to you I have been seeking thise informatio from a long time , you satisfied my Thiirst Thanking you

[@erwinpadgett1050]

Thank you for all the information you did in this video. Clear, precise, and great video with details included. This helped me greatly with my problems. Need more people to do videos like this one!

[@moterdude1959]

Very good Video I am a retired motorcycle mechanic and tinker with them from time to time still. I was very impressed with your well done video.

[@thejunkman]

Then you should check out my website for more videos.

[@grahamwilliams7578]

Thank you! Nobody ever mentions blipping the throttle to check for hesitation. I’m gonna try this today to see if I can fix the hesitation issue on my quad

[@ronfazer2423]

THanks! My Suzuki Outboard Mikuni Carbs say to tighten the screw to the right (on the airbox/silencer) to Richen it. This explains it , It is a AIR screw opposed to a Fuel Mixture screw!

[@thejunkman]

Please ask your question on my website (no registration required) I can't put very detailed information here because of the character limits. Link is in the description.

[@papajoeknows8355]

Wow, thank you so much… I’m not mechanically inclined (more like mechanically disabled). I barely knew where the carb even was, but you just solved my problem… my antique 1969 Honda trail 70 is purring like a kitten now. 👍🏻👍🏻

[@HaxNotice]

I'm chasing a reliable idle on my Amazon Kippa FCR39 and this video is helping. My carb has BOTH a fuel screw and an air screw. It's an incredibly annoying task, and I'm sure my neighbors hate me!

[@thejunkman]

It has one or the other, not both. Check out my other carburetor videos.

[@HaxNotice]

@@thejunkman It definitely has both. I purchased an extended fuel screw for the bottom of the carb to adjust on the fly, and there's an adjustable slow air screw right under the bell of the intake that changes the idle as well. It's on my DRZ400.

[@thejunkman]

I see. I missed that you have replaced your stock carb with this "knock off" FCR. I am not intimately familiar with that specific carburetor, but here is what I would do. Start with the them at some baseline and then adjust them independently until you achieve a good idle mixture and no bogging off idle.

[@thejunkman]

Don't forget to "Like" my facebook page and check out my other videos on Blip.tv cause I have other carburetor videos over there.

[@scottadkin6275]

Great Video, replaced carb on old 49 cc Honda with Chinese pit bike carb, followed your tips on air speed screw and moved the needle jet 1 notch leaner, the bike runs fine, thanks for your help.

[@deepbludude4697]

Nicely done I learned all this 30 years ago but this really helped me and my dyslexic brain get my 2008 XT250 sorted, I ended up ditching the airbox going to a unifilter and opening up the exhaust thing ran way to lean stock.

[@thejunkman]

Don't forget to check out my other videos on my website (links on channel page)

[@Cookster232]

Thanks for this guide, helped me get rid of some some annoying backfire while idling.

[@thejunkman]

Adam Cook I am glad it helped. Don't forget to check out my website as well. www.thejunkmanadv.com

[@paulsmi55]

Thanks junkman. This cleared up a lot for me on my XR250 settings ! I watched another video where it was claimed that a carb can have both air and fuel screws which totally confused me.

[@BeatersRus]

o i Fkin Love you right now....its the 4th of july and i want to ride my mini, a frankenstein with full suspension and a hemi predator/stock. bought a carb and intake kit and holy hells! am having all sorts of issues with mikuni carb pz27,found your vid which Explains things!! i will ride this bike TODAY!! thanks to You,Sir :)

[@surlybonds71]

Just want to say you did a great job explaining this concept on the video. Well done and very helpful!

[@nacsmxer]

Excellent and very informative video. This helped me a great deal in dialing in two different machines (one has an air screw and the other a fuel screw). They were in the ballpark before but now it's close to spot on. Thanks Junkman!

[@farmerdude3578]

You did a excellent job on this video. The tip at the end was great.

[@pumpkindiddler]

Thank you for the explanation at the 6:10 mark! I don't have much experience adjusting air screws and even less experience adjusting for modifications to the exhaust and or intake system. IMO, carb adjustments are easy to learn, but hard to master. This video was a great help!

[@LikeToCreate]

6:07 tip u gave is opposit Fuel screw :- tight = lean & loose = rich Air screw :- tight = rich & loose = lean air fuel mix.

[@EvendimataE]

excellent explanation.....others would just say turn the screw without saying if its air or fuel screw

[@dakotawhitaker4281]

Great job with the explanation and the demonstrations dont think it couldve been done a better way. This video alone is worth a subscribe from me.

[@TheExcessivemhz]

This video made me able to completely understand carb adjustment. Excellent tutorial. Thanks

[@bonjmin]

Alright, I did notice that the screws had blue markings as to where the should be at factory settings. I bought the carburetor off of a site that says it will fit my pocketbike. So I imagine that the manufacturers took modifications/upgrades/space into consideration when they designed it. But I wont tamper with the carburetor seeing it has already been configured. Thank you for the swift response :)

[@TechedLLC]

Nice video, I will show it to one of my students who wants to become an atv mechanic.

[@cvcoco]

thanks for this video, you said a few key things which helped me get the carb about 90% perfect today. What im left with in that 10% is when the throttle is open and held steady at half (i suppose thus straddling pilot jet and main jet) is slight lurching or hesitation. Its an unsteady throttle at half-open. Your vid cured most of it but not all. What can I do next? I have a Keihin carb on a 110cc Kawasaki. It has an air mixture screw and a screw to raise and lower the slide. It has no mods.

[@rjpaniergo1867]

thanks helped me a lot, here have a scooter carb type, done many spark plug readings and always getting lean readings, changed my main pilot from 125 to 140

[@liam6488]

So by turning the screw anti clockwise leans the mixture so if running rich you would turn it anti clockwise and if running lean you would turn screw clockwise to richen fuel mix up a bit correct as my quad was running slightly rich so i turned screw anti clockwise 1/4 turn to lean it out a little

[@csparkz]

this is the most helpful carb video i have ever seen

[@irocss85]

Really good starting point. Is there a part 2 that talks about how the needle height affects the mixture along with the air/ fuel screw. They do go hand in hand. My bike wouldn't idle off choke(vm22 enrichment ckt) at the middle Grove so I moved the position 2 down to the bottom ring Grove ( richest) setting. I'm over 3 turns out on my fuel screw. Still a bog on throttle so I'm gonna up pilot 1 larger and raise clip position 1 spot to try to get a crisper throttle transition and a smoother idle.

[@thejunkman]

Yes. I have all that information and more on this page. (Link also in the description) www.thejunkmanadv.com/motorcycle-carburetor-jetting.html

[@Kornut213]

Fuel Mix Screw is more than 3 turns Out, hence my Pilot Jet running too Lean... So what do I do/need? Bigger Pilot Jet? (recently changed my MJet from 102 to a 110) BTW, Awesome Tutorial... Easy to understand, very Clear and straight to the point. Thank You!

[@jimwhite2102]

Thank you for the education - you took the mystery out of a long standing carb problem for me,

[@liamsmith8754]

Fixed this often knowing the 2 turns out boom and that worked thanks mate massive help 🏴󠁧󠁢󠁷󠁬󠁳󠁿🏴󠁧󠁢󠁷󠁬󠁳󠁿🏴󠁧󠁢󠁷󠁬󠁳󠁿🏴󠁧󠁢󠁷󠁬󠁳󠁿

[@thejunkman]

I can't remember the exact carb you have but if it is a PWK it has an air screw. However that adjustment (this video covers) only affects the idle mixture, not overall jetting. If your plug is brown that is a good thing. Very smokey could be a sign of a leaking right side crank seal sucking in transmission oil/fluid.

[@thejunkman]

You can try raising and lowering the jet needle and or changing main jets go 1/2 step leaner or richer and see what works better.

[@juanpablogarcesramirez130]

Thank you for this, it has the small detailed explanations and visuals to help me tune my 2001 Kawasaki Vulcan 1500!

[@thejunkman]

I have a whole webpage devoted to this topic. It might help you with other jetting. www.thejunkmanadv.com/motorcycle-carburetor-jetting.html

[@xxshiftlockxx]

Thank you for the detailed explanation of the air screw adjustment. In conjunction with setting the air screw to the perfect setting, how/should you adjust the actual idle adjustment screw next to the air screw? Before or after setting the air screw? what are the optimal settings for that adjustment?

[@thejunkman]

Just set it to about 800 rpm once the mixture is set.

[@ezio8591]

very good explanation, you explained everything simply and easy to understand, thx very much, helped me out a lot to tune my ride! "If you can't explain something simply, then you haven't understood it well enough" - Albert Einstein.

[@thejunkman]

@prescole No, the air or fuel screw only controls the air/fuel mix at idle and just off idle speed only.

[@thejunkman]

@ThugsRmorons Ahhh, the beauty of the editing room. Actually I already knew where my optimal setting was for this particular engine setup, but when I built the engine and bought the carb it took hours and hours of testing to get the jetting right so it would start and run without either bogging or overheating. It was trial and error with different components to get this engine to run well. This is just a demonstration.

[@thejunkman]

well it really depends, your setting sounds like you need a pilot jet change anyways. The mixture screw only affects the air/fuel mix at idle speed. It has a negligible affect on performance off idle after 1/8 throttle the mixture screw is not functioning. Your pilot jet and clip position or needle is the area you need to tune with to get better 0-1/2 throttle performance. That is if your main jet is in the ballpark. You may want to try different jet needle profiles for even more fine tune

[@thejunkman]

It is a fairly easy procedure. Main thing is to go by what your manual says for a baseline not necessarily 2 turns. 2 turns is a good baseline IF you don't have a baseline to go with.

[@thejunkman]

@elshit1983 Find my carburetor diagnosis video and it will give you an idea on what your looking for. All carburetors function the same but look different. Find me on Facebook and subscribe/Like the page as I will probably do a jetting video in the future.

[@samanthatorres4914]

Good video learned a lot more about how these style carbs work been having trouble with mikuni carbs I recently purchased been running rich actually spitting fuel out when reved so hopefully can adjust tomorrow thanks .gained another subscriber !

[@thejunkman]

+Chris Haskell if you want even more help, check out my other jetting video. It breaks down the individual operations of the carb

[@tobythorburn7598]

this helped me a lot! my bike has been idleing very low recently, I bought it new and for the first 20 minuets it ran just great but then the revs not slower and more sluggish until it bottomed out, after I started it up it was idling very low and bottoming out a lot and this has explained it, although when the idle became sluggish is when I had throttle response issues , it would only rev up to about 80% of its potential! I have blown out the pilot jet which helped it but didn't do much so i took it to a professional and they said to check the plug and if the plug is black then it's to rich fuel and not enough air. hopefully this will fix it but I have yet to try it! (I have a 140cc pit bike with very high compression btw)

[@thejunkman]

+TobyThorburn Sounds like you need to rejet still. Check out my jetting page for help on that. There are links in the video.

[@tobythorburn7598]

+thejunkman thanks!

[@siansmalley9225]

bah. bbn

[@thejunkman]

Have you tried the idle speed screw? If it is turned all the way out so the slide is all the way down and the idle is still high or erratic you most likely have an air/vacum leak somewhere in the intake.

[@thejunkman]

Well typically with the changes you made to the air filter and exhaust usually means you need to richen the mixture, but more importantly, how does it run? If it runs ok with that jetting or runs better at least you know your going in the right direction.

[@thejunkman]

@MrMainoffice The screw on the side in the middle is the idle speed adjustment NOT a mixture screw. Your bike I believe has a FUEL screw it will be on the engine intake end of the carb on the botton and might be dificult to get to. The aftermarket makes extended fuel screws so the adjustment can be made easier with the carb installed.

[@nuttysnpdg]

you explain things very clearly great tutorial!, I have a couple of questions though; - where does the quick-adjuster for idle have to be set when tuning the actual jet? - what causes a 4 stroke to gurgle or splutter at 0-1/4 throttle, is it that the pilot is too lean? or can the needle effect that too? My bike hesitates really bad (doesn't even want to rev just dies) when cracking the throttle to over 1/3 promptly from idle.. if i hold at about 1/5th it pops and splutters. my problem when riding: from 0 to 1/5th throttle it just splutters but then if it goes above a certain rpm it jumps, it also jumps if i turn past about 1/5th.. after the initial jump it splutters again and keeps repeating that, or if i turn the throttle to about 1/3 it bogs, the only way to get proper torque is to turn it past 1/2 but then after about 3secs of not much happening it snaps into wheel-spin almost like a 2 stroke powerband!, so i let off the gas a fraction and then it goes back to bogging or gurgling and nearly throws me over the bars.. bike is a ktm 400exc that is completely stock.

[@thejunkman]

I thought I had explained it pretty well. Fuel screws are ALWAYS near the front of the carburetor where it bolts to the intake. The last part of your question is also explained at the end of the video OR you can visit my website for more pictures and information. I also have a specific page all about jetting and how to know what to change if the carb if you need to.

[@nuttysnpdg]

thejunkman thanks, I just replayed your video and now I see where you showed it... but as you may see I have edited the original post and I have a few questions.. if you could help I would really appreciate it.

[@thejunkman]

I find it hard to respond in too much detail on KZbin because of the messed up commenting system. I will try to answer your question on my website if you post your question there. However read up on this page it should walk you though what jetting changes to make. I will tell you the CV carb on the 400EX is not the easiest to tune and it is hard to get it perfect because the carburetor is not the most idea. Check for a dirty fuel system first. www.thejunkmanadv.com/motorcycle-carburetor-jetting.html

[@nuttysnpdg]

Ok I'll check out your website, just to stop confusion - it's a Keihin FCR-MX39 in a 2001 KTM 400EXC 4 stroke enduro/trail 2 wheeler..

[@thejunkman]

Nathan Stevenson See how crappy the comments are, I can't even keep the comments straight here. I see the bike model now.

[@thejunkman]

Well this video won't address your problem specifically, but it is possible a re-jet is necessary. Also that machine uses the Kehin FCR carburetor which has an accelerator pump of sorts, which may require some adjustment or modification. The FCR was know for "bogging" upon acceleration because of a fuel starvation problem with the accelerator pump cover/bowl running dry temporarily. Boysen makes a larger/better pump cover that solves that problem. However the float height might be set too low

[@sc2dave1]

Yes, i fully understand the physics behind it. What i meant is, if you can richen or lean the idle mixture, so that you have the best vacuum that way, then synch the carbs after. This is for a 4 cyl. bike

[@thejunkman]

+david contreras You could, but you have to sync the carburetors first and foremost. The best way to get close is to bench sync them before putting them on the bike. If you don't have the butterflies or throttle slides open at the same amount when the throttle is closed you will chase your tail when trying to set the idle mixture.

[@jefralynscarairconshop4880]

He vice versa the actual function of lean or rich for fuel screw and airscrew. The correct state for fuel screw when you turn it in its lean and turn it out it rich.and vice versa for air screw when you turn it in its rich and turn it out it lean. That is the correct situation of it.

[@thejunkman]

Please go to my webpage and ask this question. It is hard to answer questions here with limited space. Thanks. Link is in the description. You DO NOT have to register to leave a comment

[@TN_HondaDad]

Your a good mechanic and teacher - thanks for posting some carb101 basic settings

[@thejunkman]

As stated in the video (several times) the fuel screw is adjusted the same exact way only it affects the mixutre exactly backwards from an air screw. I used a bike with an air screw for clairity.

[@alanalilley3037]

Iv seen 6 videos on air fuel only your clip helped me thank you for keeping it simple I'll go sicscribe to your channel

[@thejunkman]

I have even more. Take a look.

[@algore1993]

can you explain more about the "hesitation"? I couldn't tell the difference. thanks a lot!

[@thejunkman]

If the engine hesitates when you turn the throttle quickly, that is hesitation. You might want to read up more here www.thejunkmanadv.com/motorcycle-carburetor-jetting.html Lots more information there.

[@algore1993]

thejunkman thanks a lot. I'm still very inexperienced

[@kiddclofilm]

Clear and straight forward

[@thejunkman]

The process is exactly the same for a 2 stroke. I used this bike for convenience and easy of showing the procedure.

[@eisemann23]

Great video, but if i'm correct, you only adjust the air screw but not the fuel screw. Do you have a video for adjusting the fuel screw?

[@thejunkman]

You are correct, however if it idles fine with that setting. Just leave it as is. If you have to turn it out much more than that the screw can become loose and vibrate out on some carburetors.

[@thejunkman]

Started life as an SSR 125 C4 but is heavily modified with a BBK, high lift cam, high compression piston.

[@Elcajonhobbies]

Great job explaining this

[@thejunkman]

I am not exactly sure what your asking but to clarify. Turning a FUEL screw in leans the idle (restricts the fuel allowed into the intake stream) mixture and turning the FUEL screw out richens (allows more fuel into the intake stream) the idle mixture. If you need more help comment on my website (link in the description) I am not restricted in commenting there.

[@salafibrouae]

@thejunkman Ok, thanks. So I need to address the main jet/jet needle or both. Will read up on this and get it to the shop. Thanks again.

[@AWDn0t2]

You did an excellent job at explaining this. My idle tuning woes are solved! Thank you!

[@frankfisher99]

Useful video, thanks.

[@thejunkman]

I don't know for sure on that model, some do and some dont't. Check with an OEM parts supplier for a parts breakdown, like Bike Bandit or something like that.

[@RidewithPhill]

Great help. Thx when I adjust the idle knob nothing happens and my 2003 Suzuki vinson idles way to high.. So high I can change the gears from foward to reverse or neutral.. I'm going to try this mix and see if it helps. I may need to replace the idle controls.If you have any other suggestions i would appreciate it.

[@thejunkman]

This video will not help with your problem. You are trying to adjust the idle speed, not the mixture. You need to figure out why the idle speed knob is not lowering the slide or closing the throttle butterfly on the carburetor. You have some other problem and doing the adjustments within this video will NOT solve your problem. You may have a vacuum leak if the idle knob is working correctly.

[@adambaboulas206]

Yeah I just went for a ride and my dad was adjusting the screws and we think the carb is dirty so we are going to clean it tomorrow or use an old one that we have

[@thejunkman]

Yes you are correct 14.7:1 but an engine will run somewhere between 13:1 and 15:1 and this adjustment tries to get it as close to optimal as possible. Remember weather, air temp, humidity and altitude will affect the adjustment

[@thejunkman]

You only have one screw adjustment (fuel screw in your case) However a change in altitude only requires jet changes. No screw adjustment affects the main jet. Depending on which way you changed elevation will dictate which way to change the main jet. Higher elevation= less air so leaner main jet is needed and vice versa. You can also fine tune "hesitations" within the rpm range with jet needled clip position changes.

[@thejunkman]

@Sk8rBoi4Lfe The idle is very simple. Find the screw that controls the idle speed (usually on the side in the middle of the carburetor) For example the idle speed screw is the screw with the black knob in the video. Turn the screw in until the RPM's raise. However if the thing won't idle at all you probably have a dirty pilot circuit.

[@MrGranit87]

Very informative video thanks, I have a fuel screw on my carb, it bogs when I throttle it, do I go in or out? Also where can I get one of these extended pilot screws as its a right pain having to take the carb off for every adjustment, thanks

[@jordanIV80]

Great vid, thanks for posting. I have a 01cr250 mostly rebuilt w/low hours, but it will only idle for a sec or 2 before dying. Is this normal or should I try to adjust. I just figured the shop set it properly. Any advice would be great.

[@cw300mag]

I checked that diaphram and looks good as far as the jets they are the factory ones and all are open

[@WLB91]

Great video! My motorcycle is a parallel twin. It's quite old (1989) and it will not run with the air filter. I've ran it fine for months without, but I'd rather have it in! If I do put the filter on the bike just bogs down and loses power until it stalls. Could the carburettor adjustment be responsible?

[@thejunkman]

Well I would clean the carburetor again because you have been running with no air filter. After that visit my Carburetor jetting page here www.thejunkmanadv.com/motorcycle-carburetor-jetting.html This will help you properly jet your bike so you can make it run with the air filters on.

[@danielfl.9347]

This video helped me 5 years ago

[@thejunkman]

Wow, and your back. Thanks. This video is now 10 years old. I have some new ones too.

[@bg147]

I have a 1999 Husky WR125 and it recently started fouling plugs like a banshee. Would it make sense for me to turn the air screw counterclockwise to increase the amount of air relative to fuel? I am also considering doing a compression test to determine the condition of the rings. People are telling me it could be the crank seal, but it seems I should check the obvious first. Thanks for the great video.

[@thejunkman]

The idle speed screw(s) are located on the side of the carburetors near the center. Your service manual will detail exactly where they are so go read that. If you don't have a service manual, you should buy one.

[@chuckspeer2163]

Thankyou to the point and simple

[@thejunkman]

Ahh, I see you caught the magic of editing. I did turn it 2 turns but in post I edited that segment down for time.

[@thejunkman]

Sorry I probably cannot help you as i don't know what you have messed with. Which carburetor screw did you mess with? If you messed with the idle speed screw that is a simple fix, just screw it in to raise the slide so the bike will idle.

[@petesanipas9341]

ok i just want to say thanks again i really appreciate your time on this thank you...

[@thejunkman]

Pete Sanipas Thanks. If you want to show some support, subscribe and share my website around if you like www.thejunkmanadv.com