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Idle mixture adjustment (air OR fuel screw adjustment) Carburetor
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- Опубліковано 17 сер 2024
- Carburetor problems? Bike have a bog when twisting the throttle? Here is how to properly adjust the mixture.
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2:20 this is an edited shot, 2 turns is just an example, your results may vary.
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Chapters
00:00 Adjustment screw locations & explanations
0:43 Initial idle mixture adjustment & general guidelines
2:33 Adjusting idle mixture with the engine running
5:34 How to know if pilot jet needs changed
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How to adjust the air or fuel screw on a typical motorcycle or ATV #carburetor. Typical procedure to adjust the idle #mixture on a carburetor. First thing to do before #jetting the carburetor
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
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.
Check out my other carburetor videos (links in the description). You still need to lean your mixture more.
I swear you worded this better then anyone ive ever heard
Ditto
I am glad you learned something and got your machine running like you want. This is why I make videos.
Carbater,is,name,four,sand,me
Thanks for providing the simplest, most informative carb adjustment video on UA-cam.
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
👋💡 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
Thank you. My dumbass was counting by clicks. Huge difference.
Thank you sir.......ATV runs fantastic now.
Cheers mate mine revs now without wanting to die it's a yx140z stomp thanks for the info on this cheers from scotland😎😎😎🇬🇧
it doesnt take that long to turn a screw 720 degrees, why edit one of the most important parts of the video?
@@tedtheturbot When I filmed this video over 10 years ago (it was originally uploaded on a different site, then here on UA-cam) 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.
Ahhh, the magic of editing my friend. This has been brought up numerous times. Notice the crossfade indicating a jump ahead in time.
This is the best way put I’ve seen on UA-cam. I’ve seen at least 10 different videos. This should be at the top of suggestions
Well share it around and maybe that will help it to the top! Thanks for watching.
thank you! this "opposite" concept has created confusion in the past but your discription helps.
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
Danielle potts I have the exact same problem and I can’t figure out what it is. Have you figured it out?
@@yungae9453 New carb, check your jets and float
If this video helped you out, consider giving a "THANKS" ❤ To help fund more videos like this!
Thks bro
Just want to say you did a great job explaining this concept on the video. Well done and very helpful!
This is the far most understandable video because he says how much turns he does Very nice and it helped a lot thanks
Wait, the turns of the screw are just a baseline. Your actual setting may be different. Just keep that in mind.
Very well explained! gained a subscriber!
I don't use UA-cam 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.
Thanks mate!
thejunkman hi I have questions my moped running but lose power
+Teresa guzman ok, need more info
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!
but you only turned the screw half a turn not 2 turns
Hunter Simmons
That was just half huh, I was so confused
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.
that was half a turn !! for sure
A turn is actually a 1/4 full circle. Anytime someone says x turns that means x quarter turns duh
Hunter Cinnamons how you count turns i don't understand
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!
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!
For me its a total new way to set the idle !!! Thanks man! It works great on my carb!
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. 👍🏻👍🏻
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.
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!
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!
It has one or the other, not both. Check out my other carburetor videos.
@@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.
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.
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!
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
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.
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.
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.
Then you should check out my website for more videos.
this is the most helpful carb video i have ever seen
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 :)
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 :)
This video made me able to completely understand carb adjustment. Excellent tutorial. Thanks
Thanks for this guide, helped me get rid of some some annoying backfire while idling.
Adam Cook I am glad it helped. Don't forget to check out my website as well. www.thejunkmanadv.com
6:07 tip u gave is opposit
Fuel screw :- tight = lean & loose = rich
Air screw :- tight = rich & loose = lean air fuel mix.
Thank you for the education - you took the mystery out of a long standing carb problem for me,
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.
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.
This video helped me 5 years ago
Wow, and your back. Thanks. This video is now 10 years old. I have some new ones too.
Thank you for this, it has the small detailed explanations and visuals to help me tune my 2001 Kawasaki Vulcan 1500!
I have a whole webpage devoted to this topic. It might help you with other jetting. www.thejunkmanadv.com/motorcycle-carburetor-jetting.html
excellent explanation.....others would just say turn the screw without saying if its air or fuel screw
You did a excellent job on this video. The tip at the end was great.
You did an excellent job at explaining this. My idle tuning woes are solved! Thank you!
Nice video, I will show it to one of my students who wants to become an atv mechanic.
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
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
I have even more. Take a look.
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.
Your a good mechanic and teacher - thanks for posting some carb101 basic settings
Fixed this often knowing the 2 turns out boom and that worked thanks mate massive help 🏴🏴🏴🏴
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
+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.
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.
@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.
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)
+TobyThorburn Sounds like you need to rejet still. Check out my jetting page for help on that. There are links in the video.
+thejunkman thanks!
bah. bbn
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 !
+Chris Haskell if you want even more help, check out my other jetting video. It breaks down the individual operations of the carb
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.
This is one of the most helpful youtube videos I've ever seen... Thanks man :)
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
ok i just want to say thanks again i really appreciate your time on this thank you...
Pete Sanipas Thanks. If you want to show some support, subscribe and share my website around if you like www.thejunkmanadv.com
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.
cool! Now i finally understand what those 2 screws are. . thanks for the vid!
Damn these new UA-cam comments, it was hard for me to find your comment to reply. Anyways thanks for the comment and be sure to check out more on my website. Lots more information there thejunkmanadv.com
Clear and straight forward
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.
Thankyou to the point and simple
What a good man you are mate! This has helped me heaps
@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.
That last sentence is what i wanted to here..try changing it on a katana. off turn on test, off turn , test one on..lol should be ready by Christmas, thanks man..
I checked that diaphram and looks good as far as the jets they are the factory ones and all are open
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.
while adjusting air mixture screw first adjust idle screw to 4000rpm first then tight the air mixture screw to its tightning position then u can see the the variation then slowly release the screw untill the engine makes maximum rotations means more than 4000rpm then adjust the idle screw .
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.
Yes. I have all that information and more on this page. (Link also in the description) www.thejunkmanadv.com/motorcycle-carburetor-jetting.html
I’m gonna do this, I’m gonna warm it up put the idle screw a little down and then I’m going to try to tune the air and fuel mixture screw
Excellent and helpful. Mixture Screw👍👍👍
the idle speed screw is very easy to adjust. Start the bike, and turn the screw in and out until the desired rpm is achieved.
The process is exactly the same for a 2 stroke. I used this bike for convenience and easy of showing the procedure.
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!
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.
Started life as an SSR 125 C4 but is heavily modified with a BBK, high lift cam, high compression piston.
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
Great job explaining this
That is easy. You have a clogged pilot jet or circuit. Check out the link in the description. I have answered this question before more in depth. If you have further questions post them there as I can explain in more detail as I am limited here.
@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.
great video 1 of the best. simple and right to the point thanks
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.
No, that is why it is the idle mixture adjustment. This setting ONLY affects the idle speed mixture. Once the throttle is open even a tiny bit the pilot circuit begins to slow as the main jet picks up. For that adjustment you need to adjust the jet needle clip position. Comment on my website if you want to discuss more. UA-cam limits me here.
I APOLOGIZE I THOUGHT YOU WERE GONNA SENCOR ME..YOUR OK DUDE YOU GET A THUMBS UP ..AND BY THE WAY GREAT VIDEO ..
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.
Ok thanks, i get it now! Actually the Optimal air/fuel mix is 14.7:1
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
@prescole No, the air or fuel screw only controls the air/fuel mix at idle and just off idle speed only.
thanks for reply a already adjustet the mixture on my polaris predator 500 same way like you explained and it works;)i needed only 1,5 hour for adjustment:)))))i have 2,5 turns out :))
The whole video is all about adjusting the idle speed mixture, I showed the process using an air screw but the process is exactly the same if you have a fuel screw. I addressed this in the video. If you are still unclear, send me a comment on my facebook page or through the website (links on the channel page)
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.
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.
Yes, a carburetor doesn't know if it is on a 2 stroke or a 4 stroke. All it knows is there is a pressure differential on either side of its throat creating a venturi effect. It is best to use a service manual if possible as the manual will give you the "correct" baseline to start with. I made this video with the understanding that most people DON'T have a service manual to reference.
Thanks to you I fixed my own motorcycle
Glad it helped!
Yes it did, being a woman, I was raking my brains trying to get it right until I watched your video, thanks again!
Great. I have some more carburetor videos coming. Please share this around and check out my website. It all helps me create more content.
How many adjustment screws are on a 125cc 4 stroke motorcycle?
Almost all carburetors will only have two "screw" adjustments. 1 for the idle speed, which is just a throttle stop for the carburetor slide and 1 for the idle mixture.
Now there are a bunch of other adjustments for jetting that aren't screws, but these are not covered in this video. This video only deals with setting the idle speed mixture, not jetting for other engine speeds.
Thought this was a really good video it helped me understand how to set up my carburettor how ever it was a different fault that was stoping my bike grime working lol but thank you this was very helpful (y)
Yes, it will work on just about any carburetor that has these adjustments. 2 or 4 stroke. I just used this bike for ease of access. Check out my website for more.
Useful video, thanks.
Oh ok. Thank you. It did not know about the clutch seal.
@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.
@AReptileMan 360 degrees. I edited me fully turning the screw to save some time, but when adjusting the screw you may only turn it 1/4 or 1/2 a turn in or out. All depends on how the jetting is for your altitude.
HAHA thanks for asking , i didn't see the edit or his annotation. I was looking at the screw. What did he save by editing out a turn like 5 seconds?? Good informative video and i look forward to more, but next time its 2 turns just show the two turns!
Thanks for making this well explained video