2-Stroke Carburetor Tuning - Idle Adjustment | Fix Your Dirt Bike.com
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- Опубликовано: 15 сен 2024
- 2-stroke Carburetor Tuning is fairly simple, all you need is a screwdriver for adjusting the pilot air screw, a strong kickstarter leg, and patience. When tuning your 2-stroke carburetor, you typically want your dirt bike to idle as low as possible without dying, so if your dirt dies after startup or idle super high, you will need to adjust the idle on your carb.
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Before you make any adjustment to the carburetor jetting, tune the idle to see if you need to change the jets at all.
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My bike idles ok but when i apply the rear brake it dies. I should mention that it has two screws one for the idle and one for the air/fuel mixture. By the way it is a 80 Indian moped with a keihin pa moa carburator.
Thank you
@@SDsailor7 When you hit the brake, or come to a stop in general?
@@Fixyourdirtbike I have not driven it yet i just recently completed the restoration i started it and adjusted the carburator and that is it. When i apply the brakes is when it dies. I was told that i need to do a compression check to see if the rings are ok. Right now i dont have the right adapter to do the compression check. If i remember right the manual says to adjust the idle until the rear tire stops turning but if i do that it dies so i had to raise the idle.
So i am not sure if i am doing the carb adjustment correct or there is a problem with compression and it can't handle a load.
Hello , can you help me with adjustment this carburator on Yamaha DT 125, I screw and unscrew it and now not have power at start , I must add throttle more times to get power
I really hope i get an answer, So my carb does have the idle adjustment knob and ive changed it. How do i reset it to a neutral position? Just twist it all the way in? but that would probably take the idle down way too much. or take it off and then do it? Ive got it better than before but the idle still is a little bit off. Idk if im making sens haha but I Hope someone can help, thanks.
Oh i almost forgot I have a 96 rm250, its in good shape for the most part.
This was the most time - efficient video i have seen in my life.
Besides the unskippable add at the start lol
It was perfect.
Hell ya
@@SimplyMage19 get RUclips red if u don’t want adds
I was Going to say that same thing
there are very view tutorials on the web that get such a good point out so fast .a screw driver,a strong leg,and patience,could not have said it better myself.
Quick and to the point with no BS, I like it!
I'm 4 years late but, thank you. Made my life way easier. I was adjusting the choke idle knob haha.
Me too
Wow, I was ONLY adjusting the fuel mixture because I didn't know there was a pilot air screw. So my bike would fire right up but die over time because I was flooding it. It was eating gas and throwing fuel onto the exhaust. Thanks a lot.
They say the more simple an explanation, the more understood the subject is. This was so quick and to the point, THANK YOU!!!
Very helpful video.
My scooter in freezing temperature was reaching easily 70kmh and with a warmer weather slowing down and I had to be satisfied with 45kmh. Now at least I understood why...
Thank you very much!
NAILED IT!! No fluff and all resolve.. KILLER!!!
Bravo! this is a master class on how to make a quick and informative video. Bike is idling like a champ now.
Fantastic video. 1 minute 47 seconds and all the information I needed. Keep up the good work!
Hey man, I appreciate the video I’m 14 and I have to do everything myself and this is my first time ever doing this and I did it first try thank you
Thank you for the quick tutorial!! My IT175 was idling super high and this did the trick. Took less than 5 minutes to adjust it properly. Thank you!!!
Glad to help!
Thank you so much for this video, on our RM85/L there is no idle tune like there is on the 125, I didn't know where to adjust the idle because it would just bog out and die after 3 seconds. I will definitely use this to help tune my bike. Thanks so much!
Thomas Harp Glad to help!
Awesome video. Easiest to follow and very very informative. I thank people like you that make it easy .
7yrs but i used ur video as guide thank you
This video was so informative and straight forward that I felt stupid for not understanding carburetors beforehand!
HAHA, thanks for watching!
Just got my fist 2 stroke and im new to the jetting carburetors. Thanks this vid helped alot
I am 5 years late but THANK YOU SO MUCH. I will try this as soon as I can!!!
Thank you so much lol just bought my first 2 stroke bike 1999 cr250 (has this same carb) and couldn’t figure out why it wasn’t running right, turns out I had my af screw turned all the way in
This video just solved all my issues in 2 minutes. Thank you
WOW ONE OF THE BEST HELPFUL VIDEO ON YOU TUBE .. NO SHIT TALKING JUST STRAIGHT TO THE POINT AND FINISH ... WHAT I NEEDED
TO KNOW ... GOOD ON YOU MATE !
Helped me start my bike after a top end rebuild 🙏🏼 thank you!
Concise, precise and straight to the point. Gotta love it.
nice vid man.now i can easily start my scooter after watching your video i feel like im the king of the world.lol
more vid to come
On a PWK35 there’s an air adjust screw and a throttle stop screw. The throttle stop screw is pretty straight forward but some input on the air adjust screw would be appreciated.
The throttle stop screw is for on the fly adjustment, and the air screw is for adjusting the base tune of the idle. Checkout my tuning guide for more info → www.fixyourdirtbike.com/fix/how-to/2-stroke-carb-tuning/
Thanks for the video i built a 2 stroke again its been long enough to almost forget the air leaks and mostly the simple things 😂😅
Thank you so much. Rebuilt my cr 125 couldn't figure out how to fix the idle cuz it idled at almost the rev limiter knew it was carb related thanks to the video I know how to fix it
Cam Ben Glad I could help!
I have a 99 cr 250 and your videos have help so much thanks very much.
Glad to hear!
Me too.. super amount of help!!
And my 1999 cr250 is doing much better..
Hey bud love the videos!! My YZ250 runs nice and crisp when it's cold out but as the weather gets warmer (Las Vegas Nevada) it's not as crisp anymore. I don't want to mess it up so i haven't tinkered with it but your video helps. I think it's running rich right now.
Thanks for watching! Yes, if your bike is crisp in the cold, but sluggish in the heat, you have a rich condition when it warms up. How drastic are the temp changes in Las Vegas?
Since I bought the engine kit I’ve never touched or took apart the carb the only thing I have the touched is the set screw with spring
My motorcycle stock at 9 years and when it cleaned the carb only it start but I can't reach 60kmh cause of "bogging" or anything and they said it's too old so that can't run , I hope this work hehe..
: Thank you for fast guiding♥️
It sounds like a vacuum leak. Check your carb body for cracks and recheck all the seals.
I have a TM 300 with the usual PWK 38. The bike starts at the first kick, cold or warm, but it tends to stall and the air screw does nothing... I thought I had a leaky jet block gasket but after a leak test, found out it's good. 42 idle jet. 175 main. The bike runs OK, the only problem is this rough idle, the tendency to stall (dangerous, expecially when going downhill on very slow/hard situations) and the air screw doesn't affect it. The carb is clean.
8 years later and this video is still the best.
Bro u fixxed my stupid gas gas 250 it was 4 stroking bad and bi mechanic was able to fix it had to to down from a 180 to 160 and main jet was a 50 and went to a 45 bc it kept fouling plugs also 1-2 gear would feel like hitting rev limiter thank you so much
I have a 05 ktm85 sx and every time I start the bike it jus opens wide up and idles as high as possible what should I do?
im having same problem w 86 it200
Sounds like an air leak from around the carb seat or reed valve seat. Check to see if there’s any air coming out from around those areas. If not, check the torque on your head bolts or your head gasket.
I had the same problem with my 04, it’s the left crank seal
Thank you carburetor man very informative very professional very well done😊
Thank you RUclips viewer. 😀
my plugs are wet and dark. what should I try first?
take air screw out 1 turn or more
How do you reset the idle knob? Do you just close it all the way or the same as you did to the air screw?
I got a 98 Yz80, and sometimes when I give it full throttle it will bog, usually in the higher gears, 4-6, it idles great, and usually when I start it, I don't have to use the choke, even when cold. I'm running 50:1
You are definitely running too rich. Try reducing the size of your main jet first, that should take care of your bogging. I would reduce the size of your slow jet too, if you can start cold with no choke it's too rich.
The idle adjustment know on the choke, how do u reset it back to neutral position? Or how many turns clockwise or counterclockwise?
Yeah I want to know the same thing...
does anyone know where to adjust the float level on keihin pj28L is it like adjusting any other float, from the base of the carb to the top of the float or is it different?
lol thanks. Finally dialed in my KDX
I'm new to bikes and have a 1967 Yamaha ym2c 2 stroke, it takes a couple of kicks to get started but immediately shoots up to redlining on the RPM's, what would be the best course of action here? Any help is appreciated
Mike Heide This is caused when the air fuel mix is too lean. This can be caused by jetting or bad seals/gaskets. When was the last time you cleaned your carb?
Mike Heide Install your exhaust and try again. You also may want to check your new gaskets and re-torque everything. A vacuum leak will cause take off too.
My kx125 revs pretty high on idle and when I rev it, it revs up good but will be idling a little higher than it was before. If I rev it up high, it idles extremely high too
It sounds like your slide or throttle cable is sticking
What a great video! I clean lots of carbs and the way you presented the info is so clean and tight including the text in extra large print.
Glad you like it!
Solid video i will try this on my bike tomorrow
Good luck!
I need to replace my idle adjustment knob. What is a "neutral position"
Bottom out the adjuster - count the turns as you unscrew - turn in to half that number = neutral
Great video. My son has Suzuki jr 80. We just had the carb worked on and it's running great, but he now has a hard time starting it. He's 9 and weighs 65 lbs and has a hard time kicking it hard enough to get it started. I can start it pretty easy when I choke it and kick it over, but he struggles where it used to be really easy for him. After it's warmed up he can start it fine. Would this be an air adjustment?
If the temperature increased significantly where you ride your carb is now running rich. Play with the air screw and see what happens. You may need to re-jet a size smaller on both slow and main.
Best ever, beats the hell out of the 20 min junk.
Exactly what I needed to hear and nothing else, thank you!
My bike has a hanging idle upon start it revs out to full throttle carb isn’t stuck open or seized brand new car just installed I’m thinking air leak also it’s a 2 stroke cr250r
That sounds like a vacuum leak, check your boot for cracks.
I meant piston and rings also have adjusted the float in the carburetor will run for 10-15 minutes and then dies animal always start with choke on
what's up man just built a water-cooled motor.motor runs and idle but when I throttle it bogs but if I run choke up it response like how it should be if it's down. running a 33 Keihin carb main-142 pilot-52 needle clip one up from the middle. but question is way does it bog? I'm assuming it's my pilot to small??? I'm like 2 & 1/2 turn out on pilot screw from the body.lmk thanks
Is you engine cold or warmed up when that happens?
What does it mean when I have oil coming out my silencer. All settings are from factory. 23 yz125. 32:1
White smoke antifreeze, gray smoke oil.. from your transmission.. crank seal failure..
My kids bikes idles to the moon n neutral, then when u put it in gear it bogs n almost dies what can cause this
Hi I have a problem I've tried all the steps you said but my bike still won't start at all I've cleaned the carb out 5 times the bike is getting gas but it won't fire I have a 1997 kdx200 with a kehien pwk35 carburetor I need help
Pull your spark and clean is as best as you can, but DO NOT replace it with a new one. Put it back and kick it over hard like you're trying to start it. Pull the plug and tell me what it looks like. While you have the plug out. Plug it in and touch the plug to the cylinder head, then kick it over and make sure you have spark. (You may need help and a dark garage)
Hi! My bike starts, goes ok on idle (maybe a lil too high) but when i give throttle the gas hangs for a bit and slowly goes down, I dont think i have it too lean. Anything i can do to fix??
How do you re set the idle adjustment knob ? My cr want ideal IV had the bike for year and never had a proper IV clean carby and new plug and still want ideal. I did take the idle screw with the lock nut out when I was cleaning it and forgot how many turns can you please tell me how many ruffly in it should be
I just bought a 93 CR125 and it idled alright. Since then I replaced the dented pipe with a FMF one and cleaned the carb as it was dirty. It starts easily but won't idle at all and the idle adjustments screw doesn't change the idle.
Double check that your carb boots are sealed and the air filter is installed and clean. Just to be safe, if you haven't already, I would go through the entire fuel/air system and make sure everything is clean and in good shape. Fuel filter, air filter, reed valve, carb boots etc. Let em know if you find anything, if you cant get it to idle message me on my FB page and we'll figure this out. facebook.com/FixYourDirtBike
Fix Your Dirt Bike thanks buddy. Yeah I strip the whole bike down clean the whole airbox so clean the air filter it's as clean as it was when it was new. I just changed the reeds to Boyesen as well and still no change. The FMF sheet says to change my main, pilot jet and needle.
Does the FMF sheet say specifically what pilot jet and needle to use? Or does it just say increase fuel flow? Either way, I'd start with a one size larger pilot jet and raise the needle by one position and see what you get. At this point small adjustments are key!
Fix Your Dirt Bike it says to use a 172 main and a 58 pilot. The clip position stays stock and the air screw 1.5 turns out. I was told yesterday at the dealer that I bought the pilot jet at that it will not affect the idle at all and that the carburetter has to be dirty still so I will take it apart yet again and make sure every orifice is clean then try it again. I bought a 58 pilot jet which I'll swap as I do t want it to run too lean. I'll let you know what happens.
Who said that? The pilot jet directly effects idle. Anyway, I can't count how many times I've cleaned a carb only to have the pilot clog when I get to the trails. Every time it's something that was knocked loose during cleaning but didn't make it out of the carb. hHave you checked your float clearance? You may have accidentally bent the float tab and it's not letting the bowl fill all the way.
How do you set the idle adjustment knob to a neutral position? like halfway in between when you begin adjusting the air screw?
Yes, the same way you neutral the air screw.
Fix Your Dirt Bike thank you so much. You earned a subscriber.
My 92 lt250r won't idle with just mixture screw have to use throttle to keep running started at 48 piolet jet now on 40 jet still won't idle do I go lower?
Have you checked your reeds? I what's the temperature where you are? Have you checked your carb body for cracks? what does your spark plug look like?
wow thank you. simple, precise great angle on the work. well done
Love the video...so I have a 1978 Suzuki 125ts with mikuni vm24 carb. One main screw on right side middle, one small screw on left side closer to air filter...I have done every adjustment possible, it will idle until I ride it and try to coast or downshift then it dies...any suggestions
Thanks! The bigger screw on the right side is the throttle stop screw, so the more you screw that in, the higher the throttle slide will sit when closed. The small screw on the left is your air screw which affects the air/fuel mix at idle.
First things first; when did you clean your carb last?
I did this on my pw80 and now it just idles really high like its about to blow up
You may have a vacuum leak. Have you done a leakdown test?
Wassup my KTM 250 2 stroke is acting up so when I ride it and try going on 4 gear it slowly turns of by itself and sometimes when i barley turn it on and put it on first gear then on second gear the throttle goes on it’s own with out me even giving it gas what do you think is wrong if you can help me out I would truly appreciate it
Bogging and taking off, that's interesting. When was the last time you cleaned your carb? Have you changed elevation or has the temperature changed significantly before you started having issues? When was the last time you checked your reeds?
Hello, I enjoyed watching it, but I have a Kawasaki KX100 bike. There is no change when moving the air adjustment screw, knowing that in the past the adjustment changes. What are the possible reasons?
Hi i have a 1994 RM 250 that just fals plugs like crazy but when I get it to go a good distince it starts to bog an even dies if im luck I down shift an it starts back up but its rill ruff an it kind of sounds like a 4 stroke any ideas pleas help
Sounds super rich.
93 yz not starting. i guess i should go with the stock yamaha carburetor settings, would yo agree?
Thanks for the great information
I have a scooter if i but the fiter in place it wont go faster because it nees more air to go in what the cause of that... And the curb dont have a air screw but the thing i know it have a big jet hole...
The ratio is correct with the air filter on. So the engine gets enough oxygen and fuel to work right.
What to do when carburetor spits fuel on the ground. When I try to kick start Suzuki ts250 fuel spits out the carburetor.
It sounds like your reed valves are bad.
my engine doesnt idle at all and when it goes high rpm when i try and make it idle, gonna chek this tomorrow bit late tonight
Possible vacuum leak. Check your rubber. Then do a leak down test if you can't find anything.
I have a 07 cr80r and tones of spark but every time I pull the carb drain plug it’s full of fuel....been a 2 stroke guy all my life lol and it’s pissing me off. I’ve cleaned it many times
Pilot air screw refers to al the screws on the carb or just one?
Just the one underneath the intake.
@@Fixyourdirtbike thank you
When i'm opening up the gass it runs great but when i'm in my last gear and i pull open the throttle, he starts to slow down and stop in the end. How is that possible and how can a stop it? I have a bing carberateur
philip starmans The next time that happens pull your plug and if it's black/wet, your main jet is too big. Let me know what you find!
I have a dt125r and the bike is starting but not idling or revving up, What should i do?
When was the carb cleaned last?
thank you for video,I have problem with carburetor,when engine is cold I close completely choke shutter and engine work idle,but after warming when I open choke shutter engine works high,max rpm and after few seconds engine falls !! can you solve this problem please?
It sounds like your jetting is too lean and too much air is getting through. When you are choked your engine is getting the right ratio so it runs right, then when it opens the sudden increase in oxygen causes the engine to take off. I would start with a larger slow jet.
I got a keihin pwk 28 carb that has been modified by the previous owner... he took the choke off and filled the choke passages with jb weld so basically carb has no choke is that bad or a good thing??
What about the idle screw? What should it be set to when your adjusting the air screw?
Josko Wrabec What bike are you working on? Your idle screw is the air screw.
The air screw can only be turned by screw driver the idle screw is usually protruding out with a spring under it that you can see. SO yes there is an idle screw and an air screw. In this video the idle screw was actually the choke knob but not all carbs are that way. if turning your choke knob does not adjust idle you will see an additional screw that protrudes out usually can grab by the finger and turn it or a flay head. Then the air screw is counter sunk into the carb only a screw driver will reach it. The idle screw lifts the carburetor slide to let more air in.
terry fonz, so which one do I adjust first? And what baseline should I start off with?
terry fonz That is the throttle stop screw. There is no fuel adjustment, that's what the idle air screw Is for. It adjusts the flow or air into the carburetor to match the flow of fuel from the pilot jet, also knows as the slow jet.
Josko Wrabec Set your throttle stop screw all the way out so the throttle plate is closed. Set your idle air screw to a neurtal position. Try to start your bike. If it starts and has a very high idle (more than the idle screw can compensate for), your jetting is too lean - go up a jet size and try again.
If you can't get your bike started, pull the spark plug. If it's wet with fuel, your jetting is too rich - go down a jet size and try again.
Can you help me out? I have a blueprinted Honda CR80 motor for my shifter kart and when I start it up the motor will rev all the way up! Like, max RPM's! It will eventually drop back to idle but only after running for a minute or 2....... what can be causing this? I took the air filter off and took a look at the carb slide to see if it's sticking and it doesn't seem to be when giving it gas on/off.
Your engine will take off like that if it gets a sudden increase of air, making the mix super lean. The reason you can stall it out is because its just oxygen burning, which makes no power. I would do a compression test, you may have a leaking gasket. If you don't have the equipment for a comp test, loosen and re-torque all the bolts on the engine. Make sure you only tighten the bolts gradually to keep the pressure even as you go.
This help me in like 2 seconds thank you
Glad to help!
All I needed to know thanks man
how is the upper screw to be not air i think the throttle screw? black with a sping on it? thanks G
That could be the throttle stop, but it depends on what carb you have.
I followed your instructions and my bike still doesn't start but it gets so close but still doesn't. do you think I need new jets?
2002 cr250 brand new mikuni carburetor starte in on choke it revs wide open no matter choke on or off tried adjusting the air mixture to still Rev wide open anyone can help me fix this issue I'd appreciate it
It sound like you have an air leak post carb and your engine is getting too much air. Check your seals, gaskets, and carb boot.
Question, when you try to start your bike the first time with the screw halfway out, are you using choke and is the engine cold?
The engine should be warm when tuning. I should have put that in there, and I have plans to redo this video.
What does he mean by placing the adjustment choke knob to a nuetral position? Do you mean half way? I have both Clymer and Honda repair manuals and both books do not have a direct answer for this on the cr125. I have read 7 clicks out and/or 30 clicks out but 30 clicks and that is with the choke fully on so there is a lot of conflicting information.
what are the reasons why poor Fuel climbing on cylinder head from carburetor
Hey my bike is a 1991 yz 250.. it won't kick over only bump, I've tried adjusting the needle, tried adjusting the floats, cleaning it out, and have tried the idle adjusting; so far no start by kick. Only bump start.. however when it does start its like the throttle cable is stuck wide open, but it is not because the throttle it's self still moves normal when used; snaps back and all, so my question to you is what could be causing it to have such a ridiculously high Rev.
I'm saving this video just in case my dumbass forgets lmao
Mine runs/idles with the needle seated… confused on how to approach the problem, or is it a problem?
I have a motorized built and tried adjusting screw to set idle but It struggles to stay running and tried running the screw like has been shown all the way in till it idle but my problem is when it does idle and it starts it throttles it self without twisting throttle could you point me the right direction thanks
Did you rebuild your carb recently?
Do you know anything about racing carburettors I have a racing carburettor on one is it any different
I bought a lectron carb hav any insite on that? The bike starts almost always first kick but I have to turn the choke on to get is started. But turn it off fairly quickly otherwise the bike will die.
first it fouled while ideling then I put a new plug in and it lasted one tank.then the next day I started it idled fine then I rode like 100 yards and it fouled out while riding.i took it out and its wet and dark and will not spark anymore.
I would start by changing your main jet to a smaller size.
Help! I have an '89 KX250 that won't idle without a tiny bit of throttle input. However when I do that, it idles just fine. No matter what I do with the idle speed screw AND the pilot screw (Keihin PWK 38 carb) it still dies. Ideas? Thanks!
cdnbluesdriver first things first, have you cleaned your carb recently? if you have, have you turned your idle screw all the way in or out to get as close as to idle as possible?
My problem is not the start it starts by barly even trying even before the new rings but my problem is that i fould like 10 sparks plug in May like i would ride it one day with a new spark plug and next day it would fall so i put new after new it wasnt annoying at first but last week i went riding and i fouled 2 spark plugs it was fill with oil is this the problem?
Either your mix is too rich, you are idling to much, or both. How do you ride? Woods or MX? 2 strokes need to be under load keep oil flowing through the engine. so If you find yourself idling a lot or riding to slow you will see plug problems, and rich jetting will make it worse.
Also, are you using the same model of plug every time? Is it the OEM plug? If you are using a plug that is not designed for the ignition system, you may be getting a colder spark than you need. If you are using the OEM plug, your ignition system might be failing.
Wait, am I supposed to count the idle screw turns out from where it doesnt turn in anymore or when it's flush with the carb?
When its all the way turned in.
Why does my bike idle high for like 10 seconds then shut off after I give it throttle. I already checked for vacuum leaks and tried adjusting the screw
What you described is definitely a lean mix. Either it's a vacuum leak or your throttle stop (if you have one) and idle screw are set just lean enough to idle high.
Please help.
Just bought a 1970 Suzuki TS 250 and carb was leaking.I had a carb i took off a good running TM250 before i restored it and put on this TS 250.Bike starts nice but idles high and is dead in middle range,no power to lift wheel.Full throttle hauls butt and idles nicely although too high in my opinion.
What shall i look for ?
TIA
Dennis Dillman lower your needle one position and see what you get. You may need to get a smaller slow jet also.