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.
@@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.
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.
Please ask your question on my website, you will get better and faster help there. These new UA-cam comments suck and I don't like them. thejunkmanadv.com UA-cam 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.
That shouldn't be? Should be able to just put in a name (anything) and an email. UA-cam 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.
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
@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.
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.
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.
Please comment on my website so I can fully explain what MAY be the troubles. Also please be as detailed and concise as possible. I do not have enough room on UA-cam to fully answer your question and give recommendations. I will try to help if I can. Thanks.
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
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.
I said two turns and turned the screw two turns, the annotations should have explained that there was an edit. If you have other questions leave them on my website (link in the description) and I can help you further.
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
Please leave a comment on my website so I can comment easier and direct you to a link if need be. Link to my website is in the description, you DO NOT need to register to leave a comment there.
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 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.
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 :)
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!
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
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.
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!
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.
@MrMainoffice You can contact me via my website. For the idle mixture there are two different kinds AIR or FUEL screws no carburetor has both. Your bike most likely has a fuel screw. Follow the instructions in the video. Contact me via my website and I can try to help you more if your still stumped.
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!
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!
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.
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.
Please ask your question in the comments section of my website (link in the description) because I am limited in my response here. You possibly have multiple problems.
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)
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.
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.
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
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!
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.
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
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
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 :)
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.
@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.
@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.
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
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
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.
My 49cc huasheng scooter is taking off when idle ing. Like I am pulling the throttle just a little bit. With my old mini bike this happens but differently. It used to take off then make a weird sound then shut off. But we figured out what it was. This is different. I don't think it has to do with lubricants because we do matnence correctly thanks!
@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.
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.
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.
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
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.
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.
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.
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 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
@HopeForBipolar Carbs have one or the other not both. They are adjusted using the same proceedure just the operation of each is oposite. I cannot give a recomendation being I don't know what you have (an air of fuel screw) Towards the end I explain in general which way to go leaner/richer depending on what screw type you have.
@salafibrouae Yes you are running too rich, however the blackend spark plug is from overall jetting not just the idle mixture. This proceedure just adresses the air/fuel mix at idle so you don't foul plugs or over heat while idleing, as well as taking care of any tendency to "bog" off idle. Your problem lies within the main jet, jet needle or both.
The needle closes the main jet at idle so your only running on the pilot circuit. Buy an assortment of pilot jets and play around a little. You can also get some micro drill bits to use as a crude measuring device and compare the size to a known jet size. As for you intake, experiment with building your own velocity stack and use a pod style filter. The intake will roar and be loud so if sound is a concern work with the stock air box.
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.
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.
👋💡 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.
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
If this video helped you out, consider giving a "THANKS" ❤ To help fund more videos like this!
Thks bro
Thanks for providing the simplest, most informative carb adjustment video on UA-cam.
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.
I swear you worded this better then anyone ive ever heard
Ditto
Don't forget to check out my other videos on my website (links on channel page)
For me its a total new way to set the idle !!! Thanks man! It works great on my carb!
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.
Ahhh, the magic of editing my friend. This has been brought up numerous times. Notice the crossfade indicating a jump ahead in time.
Please ask your question on my website, you will get better and faster help there. These new UA-cam comments suck and I don't like them. thejunkmanadv.com
UA-cam 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.
Paul Turner
That shouldn't be? Should be able to just put in a name (anything) and an email. UA-cam 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.
thejunkman how do you adjust the fuel it on 2003 polaris trailboss 330.cant get under carb with screw driver
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
@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.
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!
@ROBOTNINJA500 Thanks for watching! Like my facebook page for more tips and tricks like this.
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
Please comment on my website so I can fully explain what MAY be the troubles. Also please be as detailed and concise as possible. I do not have enough room on UA-cam to fully answer your question and give recommendations. I will try to help if I can. Thanks.
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
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.
I said two turns and turned the screw two turns, the annotations should have explained that there was an edit. If you have other questions leave them on my website (link in the description) and I can help you further.
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.
thank you! this "opposite" concept has created confusion in the past but your discription helps.
Thanks, if you have more questions, please leave them on my website (link in the description) as I can help you better there.
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
Nice video, I will show it to one of my students who wants to become an atv mechanic.
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.
Please leave a comment on my website so I can comment easier and direct you to a link if need be. Link to my website is in the description, you DO NOT need to register to leave a comment there.
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.
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 :)
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!
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.
Thanks, be sure to like my facebook page and check out my websites for more! Links on my channel page.
Just want to say you did a great job explaining this concept on the video. Well done and very helpful!
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
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.
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!
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.
Thanks be sure to check out my website for more videos. You can comment there if you like.
@MrMainoffice You can contact me via my website. For the idle mixture there are two different kinds AIR or FUEL screws no carburetor has both. Your bike most likely has a fuel screw. Follow the instructions in the video. Contact me via my website and I can try to help you more if your still stumped.
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!
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
@prescole No, the air or fuel screw only controls the air/fuel mix at idle and just off idle speed only.
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!
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.
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.
this is the most helpful carb video i have ever seen
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.
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.
Please ask your question in the comments section of my website (link in the description) because I am limited in my response here. You possibly have multiple problems.
Yes, if you have other questions please ask them on my website (link in the description)
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)
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.
You did a excellent job on this video. The tip at the end was great.
Thanks, check out my other videos over on Blip. tv links are on my channel page.
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. 👍🏻👍🏻
@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.
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.
Great job explaining this
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
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!
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.
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
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
6:07 tip u gave is opposit
Fuel screw :- tight = lean & loose = rich
Air screw :- tight = rich & loose = lean air fuel mix.
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 :)
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.
excellent explanation.....others would just say turn the screw without saying if its air or fuel screw
@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.
Started life as an SSR 125 C4 but is heavily modified with a BBK, high lift cam, high compression piston.
thank you for your video it was very very helpful
@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.
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
You did an excellent job at explaining this. My idle tuning woes are solved! Thank you!
Where should the idle screw be when adjusting the mix screw?
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
Be sure to check out my website for more tips and great videos.
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.
My 49cc huasheng scooter is taking off when idle ing. Like I am pulling the throttle just a little bit. With my old mini bike this happens but differently. It used to take off then make a weird sound then shut off. But we figured out what it was. This is different. I don't think it has to do with lubricants because we do matnence correctly thanks!
@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.
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.
@elshit1983 Not sure what your talking about there, but some carburetors have a "jet" for high altitude (leans the overall jetting)
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?
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.
This video made me able to completely understand carb adjustment. Excellent tutorial. Thanks
The process is exactly the same for a 2 stroke. I used this bike for convenience and easy of showing the procedure.
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
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.
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.
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.
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.
Thanks. Be sure to check out my show over on Blip.tv /thejunkman for more carburetor videos as well as other videos not on UA-cam.
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 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
Very good video! Thanks!
@HopeForBipolar Carbs have one or the other not both. They are adjusted using the same proceedure just the operation of each is oposite. I cannot give a recomendation being I don't know what you have (an air of fuel screw) Towards the end I explain in general which way to go leaner/richer depending on what screw type you have.
@salafibrouae Yes you are running too rich, however the blackend spark plug is from overall jetting not just the idle mixture. This proceedure just adresses the air/fuel mix at idle so you don't foul plugs or over heat while idleing, as well as taking care of any tendency to "bog" off idle. Your problem lies within the main jet, jet needle or both.
The needle closes the main jet at idle so your only running on the pilot circuit. Buy an assortment of pilot jets and play around a little. You can also get some micro drill bits to use as a crude measuring device and compare the size to a known jet size. As for you intake, experiment with building your own velocity stack and use a pod style filter. The intake will roar and be loud so if sound is a concern work with the stock air box.
Thank you for the education - you took the mystery out of a long standing carb problem for me,
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