In this video I go over every part of how to tune a Carb while its on the bike. Starting from the pilot system to the Needle system and finally the Mains. This video is for 2 and 4 strokes.
You got a great video man it's right to the point is easy as ABC I've been a mechanic my whole life but you know you still look things up just to bring back that memory I'm in my 60s but listen to you brought back everything instantly it's like don't overcomplicate things
@@TheMotorcycleForge I got my motorcycle up and running thank you it might as well be a piece of junk without that carburetor running just right now I'm Papa-Wheely back on the road again 😜
@@TheMotorcycleForge I Am have a little issue with my 21 mm OKO Carb. I am at 5000 feet elevation. I'm having a hard time getting the bike to idle after warmed up. It seems to only one idol at 2500 RPM or better and even at that it's not very stable. Could you recommend a good starting point for my idol jet. The main jet seems to be fine. I'm running a 80 in it right now and a 35 idle jet. I've checked for air leaks and don't have any. I really appreciate your help with this issue.Thanks DC.
@DirectCurrent4u At a guess, I would think it may be a bit rich on the idle circuit. Have you tried altering the mixture screw? I explain how in this video. If you have, I would try a 30 idle and see if it improves. By my calculations, you are running rich on the idle. Go down in small increments until the bike is happy idling hot but just needs a little choke when cold. Might even be as small as a 22 idle jet.
@@TheMotorcycleForge Thank you for your reply! I think the smallest idle jet is a 30. But if that is not low enough I will try to find some smaller ones! I will let you know how it goes when i get there. Thanks again for your help! Cheers DC🙏🏻👍
Thank you! Helped me a lot. Runs a lot better, from the start ant overall, haven’t messed with the main jet though because I’m currently doing a break in on my new Polini Corsa 70cc So I’m not using full throttle. I still have some tuning to do but for now I’m very pleased after watching your video and tuning my moped. 👍😎
Love your ol dt175 have an 81 xt500 was my first bike I purchased at 18 and I'll never get rid of that gem. Insta sub, excellent explanation, and even better taste in bikes❤
By far this is the most realistic on how to tune a idle carb! while the other places explain like it some kind of quantum physic science making it nore complicated then it shouldn't .
@@TheMotorcycleForge You may laugh but it's a heavily modified Hawk-250. I love working on these things for some reason and this bike is super cheap to work on and learn. My next project will be to restore something more classic/iconic. Again man, thanks for the help with it, the pace and info in this video is absolutely perfect.
very nice explanation! i didn't know that lean pilot jet can cause a slow rpm return when closing the throttle which i am experiencing right now on my bike. it's a little bit complicated because my carburetor has accelerator pump so i have more things to get working properly
Thanks man much appreciated. The only thing to remember with the accelerator pump is it adds fuel with throttle movement (rolling it on) but not when holding the throttle at a fixed position like 50% for example. What is the project bike?
I have a problem with my KTM 250 2T The tool has not been used for almost a year This week I found time to take care of it, I did a fuel-oil change, I cleaned the filter plug, everything, finally I tried to start it, but the car could not start. It only started with carburetor spray and shut off straight away From that I understood that the carburetor needed to be cleaned and that's how I did it. Now the problem is different, the motorcycle drives straight up to very, very high turns I played with the air-fuel screw but unfortunately it didn't help. Is there a situation where the problem is different? Something in the carburetor maybe? need help pleases tool,
@kobiisrael10 Make sure the jets and atomizer are fully clear in the carb, it may be lean from a blockage. Make sure it has fresh fuel as well. There should be no residual dried fuel in the carb body and other parts. Once everything is spotless, it should run correctly. If not it may need the idle speed and mixture altered.
Ive got a 1994 suzuki ds 80 and a brand new PWK nock off d slide carb and i can NOT tune that thing 😭 please advice. Its a 80cc 2 stroke enduro bike. I have 110 main jet in it idk abt pilot jet. I have a spare 115 jet and a 110 jet but its longer than the 110 in the carb rn Edit: it has a screw by the float bowl (air screw maybe?), a idle screw and a screw on the top of the intake where the air filter goes (mixture screw i believe) Edit: no it does not run or idle it only fires
Hello sir, i have an old Honda xl185s and im looking to tune the carb, stock carb/settings but it high speed its stuttering but when i open the throttle fully the it cuts out and then cathes up
If you have a accelerator pump that may be the cause or when cracking the throttle it's getting a big gulp of air and leaning out till the fuel catches up.
I have a 35 pilot in mine and im not sure what main i have but i cant get it to idle smoothly abd when i give it gas it takes about 5 seconds to idle back down from quarter throttle. What should i do
@Thomas-b4m1p it's running leanon, you will need to richen up the idle mixture and adjust the idle to suit like in the video. May also need a bigger idle jet if that doesn't work.
From my observations, each carburetor component affects the entire rpm range. Take the example of the main jet - it is said to work 3/4 to full. To check that theory its enough to put a jet half as big as needed - the motorcycle will not even start from 1st gear. Engine will just turn off. And the same that too large - it will flood. No less good work - explains a lot.
Interesting observation. The jet needle has the same diameter at the top but it becomes long and tapered. As the carb slide lifts the taper starts to allow fuel to pass. So the idle jet starts it off, then as the slide goes up, even a little in first gear, the idle jet maxes out, fuel is needed to balance the increase in air, so the main kicks in to help. The main is helping but not yet carrying the load of fuel it is capable of. When you think about it, the carburetor is a masterpiece.
Unfortunately I don't know of any kits either so when I need a main jet smaller than 100 I order them individually from these guys as they are my nearest stockest. www.motorcyclespareswarehouse.com.au/products/keihin-main-jet-large-hex
Is it bogging when you give it full throttle like a jab and stumbling no power after changing your carb? I got a defective JFG flat slide carb I could only tune idle and that's about it I bought tiny jets like 40 I'll try to find the link
@@calambres6614 it was bogging bad but I started to increase the main jet size and it keeps getting better. I would of never thought it would take such a big jet but it runs great now. At least now when I put the G2 reed valve and pwk carb on my phantom 85 I'll have a lot better idea where to start but I'm waiting for someone to make an expansion chamber for them so I can do it all at once. A good expansion chamber would really open them up and if nobody makes one by next summer then I'll try to find someone who can make me one using the stock exhaust for the flange. I'll pay the person obviously
Hi, i have a 26mm one of these carbs on my YX140 pitbike and its running like a bag of shit. It has a 85 main jet and a 45 pilot jet. Can you help me to get this to run right. I have a 102 jet which i can install but idk if its a good idea or not. Please help
I haven't jetted a predator engine before but if it's a pwk carb or similar. I think a 145 main and 45 pilot jet should be a good starting point. You could start one size richer to be super safe but this should be pretty close.
@Smodlee Could be either very rich or very lean among other things like float height too low. You will need to do some testing to figure out which one it is.
As long as your throttle cable has the correct fitting on the carb end it's pretty easy. Just compress the spring and locking tab up to the carb top and put the end of the cable in the cutout in the slide and release the spring & locking tab.
High idle can be from a few things. Throttle cable is adjusted to tight. Something is stopping the slide returning to the bottom, Im guessing you have adjusted idle speed screw already? Bike could be to lean on idle circuit either from incorrect jetting or you may have an air leak.
I would start with a 115 main and 42 pilot which is a good starting point and see how it goes. Then after you could try a 112 or 118 main to see if it gets any better. .
Okay can someone help me becouse i dont fully understand english so if someone could detect problem for me i would be thankful. I have problem with my carb cuz i have to rich fluel and my spark plug is almost fully black( and burn in about 2 mth) . On the leanest fuel setting it still happens for my spark plug to be fully black. I also wanna mension that my true powerband in my 2 stroke is hard to get.
What happens if the pilot is extremely lean From factory my pilot is 75 and main is 160 I have a jd jetting kit and it’s telling me to put a 50 pilot and 170 main
Generally bike will be slow to return to idle if to lean on pilot jet., may pop a little on decel depending on bike. I think a 50 would be ok, if you follow the video I give a full list of symptoms and how to tune the carb.
Hi mate, i just have a question i have an 150 cc bike it's all good everything's working fine but there's this issue when i turn the throttle full the acceleration is dull but when it's 3/4 throttle it accelerates very fast & idk what's wrong the cable or something
So detailing explanation. Greetings from Greece. Thank you for this video and all the useful info, man, but there is something i can't get over. Idle is always too rich on my pwk 28 keihin. I'm running it on an yx 150 ksr type engine. Idle jet is 32 main jet is 108. I don't know what's wrong with these carbs. May there be a problem causing that? I'm talking about the engine flooding with fuel from idle to 1/8 throttle, the rest is perfect. I can't find amy solution anywhere. I hope you could provide some helping tips, brother. Thanks again!
What adjustment is the mixture screw at? Also there might be a small peice of material causing the float valve to leak or the float might be set a smidge high for perfect seal.
@@TheMotorcycleForge even if i completely remove it, the motor still runs too rich. I took it apart an hour ago, blew some air through all holes and replaced the needle. The idle now is more stable and the first eighth of the throttle is great but now i got another problem and i guess i need to play with the needle position and main jet. It bogs at 1/4 when opening the throttle after cruising at less than 1/4. Bogs a bit and goes along. Screams lean but I'm not sure.
For the needle I recommended these two, N80F or JJY and I would start in the middle grove and see how it goes. May need to lower the needle/lift the C clip depending on bike. Hope this helps.
my bike dt 125 newly rebore and i use yamaha rxt 135 piston with ring. also use 4 stroke carb yoshi r 28mm i use 120 main jet and pilot jet 40 run it perfect. but i want to replace it with my stock carb mikuni 24mm the stock jetings is 165 main jet and pilot jet 22.2 the bike not run. what jetings can u recommend. and tnx for the video i got an idea
So does it not run at all or just rough? Give the stock carb a good clean and make sure no jets or passages in the carb are blocked before changing jets.
So jetting from mikuni is difficult to keihin for example. A 100 keihin jet is the same as 200 mikuni jet. Pilot on the mikuni may be to small nut cant hurt to try some different jets
hello, nice video! thanks. i recently bought a pwk34 for my bike and i got it running ok i guess but i have a question: what does the screw besides the negative pressure hose do? it doesnt seem ajustable since it doesnt have a spring so unless is tighten it surely come off with vibration. should i keep it tight or unscrew it ? please help! anyways good video i got my mix right thx
So if you are talking about the screw above the intake trumpet/ air filter side. It's supposed to be for adjusting the power jet/ it's for two strokes but personally I normally don't use it as it makes tuning the main jet a little more complicated.
@@TheMotorcycleForge i have a 4 stroke so im not even touching it now that i know haha thank you! my carburetor came with 2 spare main jets, one pilot and another needle to set it leaner i guess (the number is smaller on the spares). i have my engine running decent with almost 3 turns out so i have to change some things. should i change the needle and pilot too if i put the smaller main jet? or is it enough with the later. thank you in for your time to reply. i really appreciate it
If you have the pilot circuit working well at low rpm you shouldn't need to change it when you change the main jet. The needle is just for the part throttle/ mid range so I would only change it when alternating needle height doesn't help.
Hi, I'm from Argentina and I bought a fxr 150 but it came with a honda tornado carburetor, a keihin 32mm, I understand that the chicler measurements between keihin and mikuni are different and I don't know of an equivalent, I know that the original fxr is 27.5 idle and 115 main, I would like to know which keihin chicler could go well, by the way, good video
So I run a 30mm keihin pwk copy on my fxr 150s. With around 40 pilot and 112 main jet. A 32mm carb is probably a bit big for a fxr150 but I haven't tried one so not 100% sure.
What is a good jet size for a china 150cc Enduro with a big bore kit with 65mm piston, 26 mm flat slide keihn carb and yashumira exhaust. Right now I have a 40 pilot and 110 main, clip in middle on needle. It is a 4 stroke. It back fires on deceleration. I tried a 115 main and worked without connected to filter and airbox. Connected to airbox I have to drop to a 110 main jet . With the big bore kit the 150cc should be somewhere between 180 and 200 cc. I will try to open airbox a little to low for bigger main. I was thinking maybe changing pilot from 40 to 42 or 45 to help get rid of backfire on deceleration. Seems to run ok through out the throttle range, could be a little better I think. No bogging but not great acceleration on top end.
Ok so your on the right path with the backfire, a bit richer on the pilot jet should help or try turning the mixture screw in a 1/4 may also help. I think a 110 main in a 26mm carb is probably to big. I run a 112 or 115 in 30mm carbs on our 150cc bikes. Maybe a 105 might give you more acceleration. Last but not least if your engine is 180cc to 200cc a 26mm carb will probably limit top end power , depending on what your bike revs to and its stroke. Hope this helps.
@@TheMotorcycleForge when the bike was 150cc before the big bore update I tried the 28mm flat slide and it simply did not work, poor performance. On a Kawasaki kmx 125cc 2 stroke the 28mm worked fine. On the 4 stroke china bike I had no luck, once I tried the flat slide 26mm it worked, and jetted easily except for the deceleration backfire. I'm a little worried about going to a 105 main it might be to lean. It ran good with no filter on top end with a 115 main. It runs ok on top end but not as good as the 115 without filter. Don't want to run bike with no filter to much rain and dirt here. We will try to open air box tomorrow and see if that allows for a 115 main. I will bring a 105 main if the 115 does not work. I tried adjusting fuel/air mixture screw but did not get rid of backfire.motorcycle is heavy. I have a rack on the back to carry a top box and 2 water containers 20 liters each, around 5 gallon. It's my typhoon, shtf bike. My other bike is a Yamaha aerox with the 155cc engine. Great bike but a scooter and is boring as hell. My girlfriend won't ride on china bike. She's scared of it. Plus it's high off ground like most dirt bikes are.
Sounds like you have everything pretty sorted. If the airbox mod doesn't work you could try a 108 instead of 105. Only other thing I would try is a get a air fuel ratio gauge. Will make tuning simpler as bikes can pop on decel when lean and rich.
@@TheMotorcycleForge thank you for the feed back. I live in the Philippines on an island surrounded by the Pacific ocean. No fast food or malls here. Can order things, takes weeks to get. Maybe we can get maybe 10% of the variety Amazon sells. I have jets from china they are 110-115-120 etc. I order jets for pwk slide carb from different sources and see if I can find something. I prefer adjusting jets up or down at 2mm at a time instead of 5 at a time. Will check spark plug also to see if running rich or lean. I only have 200 km on the big bore kit. I only have about 800 km on bike and when I bought the bike new the place I bought it from said they put 20w-50 full synthetic oil in it. I wanted regular oil for break in and I had to drive around 50 km to go home. Checked oil when I got home and it looked like clear fluid with zero lubricating property's. Changed the oil right away with a good non synthetic 10w-40 oil but the damage was already done. The bike ran ok but it belt like I was driving a horse and buggy, so slow I could not stand it. When changing cylinder the cylinder walls were scared at 500 km. All because what ever oil they put in the bike was useless. I should have had the dealer change the oil with oil I provided. You shift in second and give the motorcycle gas now it will throw you back in the seat. The speed shop that sells the big bore kit rates it at 180 cc. Me and the mechanic both feel it's more in line with a 200 cc. So close to having it running the way I want it. The bike hauls a*s. But could be a little better. Police here have been known to tear the muffler off on after markit exhaust if to loud. I have a db killer baffle installed in muffler which makes it a little less noisey. If I get rid of the back fire I can keep the pipe longer.
Dam that's a pain about the shipping thing, really makes projects take a long time. Sounds like the bike is a ton of fun to ride, yeah synthetic is pretty crap for running a motor in, the dealer should have known that. Do you know what the stroke of the bike is?
I had a nibbi carb spent.3 hours on this and it still screwed when.you.rap the throttle it would just.cut.out.Think i.got.a.defective carb no matter what I tried something going to try a different brand
Ok at a guess 108 might be a bit big for a 26mm carb but if you have tried leaner and richer maybe it is the carb. I would try a 100 main jet and if its better after that try a 98 main.
As I understand it the power jet affects only full throttle so I would tune that last and use the same technique as tuning the main jet, I avoid using power jets as there is no real gain on the bikes I use. Hope this helps
@@TheMotorcycleForge yes, there's not a whole lot out on how to use, or what the proper procedure for setup after everything else is good. I appreciate your time friend. Thank you.
First thing to check is that your throttle cable has some free play as it might be holding slide open a bit, Second make sure nothing is obstructing the slide from closing properly, lastly it might be lean on the idle jet so a bigger idle jet may help.
@TheMotorcycleForge @TheMotorcycleForge thanks! Used a jetting calculator and can't get exact sizes... Stock 4th clip down. 160 main, 45 pilot. Used two calculators. First was to see jetting for aftermarket exhaust, second Used the values from the first. 155 main, 3rd clip down, and 44 pilot.... The reference of your almost 5 turns down to 3 moving from pilot 50 to 45... so stock states 2 turns out on the air screw, to get closer to 44 the calculator came up with.. I'll be aiming for somewhere between 1.5 to 2 turns out.
Well I would check the basics first, what is the plug condition like? Is the sparkplug gap correct. Set up the carb correctly, float height ect. Go from there, if still no luck consult who you purchased it off.
I have a am6 engine with a big bore kit, exhaust and all that stuf and i had a dellorto 21mm carb on it and it ran fine with it then i got a mikuni 28mm flat slide carb and the problem with it is that when you give it quick full throtle it bogs down. I tried biger main jet, tried different float settings and nothing realy helped. Its got a 32 pilot and 150 main jet. Please help i realy want it to work good again.
I would possibly try altering the idle mixture it may only need 1/4 turn in or out but my guess is that the carb is probably a smidge big for that motor. Does it accelerate smoothly when you roll on the throttle slowly?
Yeah that's the same with our race bikes and the conclusion I came to is because the carb is a bit big for the engine. At low speeds the rapid change in throttle is to much for the engine but it will still gain some power up in the high rpm as a result.
Using google translate as I don't quite understand what you mean. Every bike is different so your jetting may be much different than mine. Hope this helps
Can i get your Instagram please? Im so interesting about how you tuning about 2 stroke,i mean in Indonesia we are tuning 2 stroke,even a chainsaw ,i want to sharing about motorcycle 2stroke with you i have a question about upgrade 2stroke ,port ex,carb,comperssion everything,thankyou🎉
@ernysetyaningwati5257 I currently don't have Instagram but I have a email on my channel page which you can send messages and pictures ect. Would be happy to help.
Looks like is misfire at full rpm is it possible the mix oil in gasoline in the tank is too rich because was okay before with 1 n half turn on adjustment srew, since I did the mixture too rich in oil starts to do this
I've got a PWK 30 JRC Power Jet on an old 1972 Triumph 650 - Thing runs fantastic EXCEPT the choke/enrichener has to be on. As soon as I turn it off, the bike stops. - I heard it was pilot jet, but I took off the bowl, removed it and it was clean...ran a guitar through all the little holes...any other ideas?
@retromototoys I would first have a go adjusting the mixture screw and idle adjustment. Also make sure the idle jet is correct and that there is no blockages in the carb body.
Man thank you so much great video! I've been trying to tune my pwk for my pit bike and no such luck until I found your video thank you brother! Grip it and rip it!!
Great video sir, I have a Honda XL 650 the Orignal carby was shit so i bought a PWK 36mm and it's so much better, I recommend the PWK Carby on any older bike
Ok so first, have you made sure a nothing is clogging the pilot jet or any part of the idle circuit. What pilot jet do you have in it? Will it idle when you turn the choke on?
