How to install fuel mixture screw on 4 stroke dirt bike - Keihin FCR carburetor

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This video shows how to install fuel mixture screw on 4 stroke dirt bike, for Keihin FCR carburetor. This carburetor is used by majority of dirt bikes - Yamaha, Honda, KTM, Suzuki, Kawasaki..
This in an inexpensive way to allow you to easily adjust your carburetor due to elevation and whether conditions.
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fuel mixture screw 4 stroke dirt bike

[@landonlewis333]

Thanks for actually letting us hear it while it was bad

[@stampydragon2739]

I love this how he shows you adjust and talks about why it’s important as a mechanic I appreciate the fact he’s passing on knowledge to the average viewer who may or may not know

[@motoaz3963]

You saved the day again now to get that mixture screw. I've been fighting mine for months now, who would have thought the air fuel mixture.

[@dirtniron]

cool man! glad it helps!

[@diarmuidoc9427]

Enjoying these vids on the WR, great information. Thanks for making them Rado. 👍

[@dirtniron]

Thanks bro, I am glad it helps!

[@pahuntco9461]

really good explanation!! thank you so much for showing how to bike reacts when you turn it up and down

[@dirtniron]

thanks, glad it helps!

[@noahkloeck5870]

Super strait forward. No bs. Great vids man.

[@dirtniron]

thanks Noah, appreciate the feedback!

[@brendonchase9460]

Awesome vlog. Great tips and easy to follow your visual demonstration. Thanks heaps

[@dirtniron]

Glad it was helpful! Thanks Brendon

[@user-dy9bm7sk7n]

Great video, thanks for posting....hi from Australia :)

[@hugovignati1420]

Desde Argentina te saludo, excelente tu canal, tengo una WR450 2008. Gracias!

[@c00t999]

you're a legend ! Thank you for the reasons why ! About to do this on my drz400sm mikuni carb

[@dirtniron]

Glad I could help

[@physics1874]

Thank you so much great video. I’ve been looking for the problem with my super high idle on my 250 and I think this might be it

[@secristshow1616]

Thank you for the video, my friend. Very helpful.

[@nickj250_]

very good video right to the point it helped me alot. love this channel

[@dirtniron]

thanks, glad it helps!

[@johndeere2cylfarmer]

Another great video! Keep up the good work!

[@dirtniron]

Thanks Hunter, appreciate it!

[@antoniheartt7007]

helped out appricite how u let it run and showed before u set it and after it's set proper

[@smithkenny4450]

It was really a headache to adjust. thank for this Kevin.

[@dirtniron]

you are welcome !

[@akathecanadian]

Nice! Easy, quick and to the point

[@dirtniron]

thanks Joshua!

[@jiapaguilar2495]

Good job sr!

[@RedBaroness12]

this helped me alot thanks !!!

[@dirtniron]

Glad it helped!

[@wendyadomaadoma1462]

Nice tips.

[@31bradi]

J'ai remonter une épave de 2003 yz250f .. j'avais ce problème merci pour cette vidéo 🙏👌👌👌👌👌👌

[@jbtwo1733]

Thanks for showing how the spring, washer, and o-ring are assembled!

[@dirtniron]

Glad to help!

[@epann2921]

@@dirtniron I found several images online showing the washer and gasket below the spring. How on earth can I verify which is the correct way to assemble.

[@Skippstar]

Awesome video. Bike now purrs like a kitten 😁

[@fynn8252]

I'm having the exact same problem as shown in the beginning of the video. I have a KTM 525 and it's also a Keihin Carb (looks exactly like yours). But no matter the position of that fuel mixture screw, the bike will not want to start. I played with the idle screw as well but no luck. I took apart the carb to see if the jets may have been clogged but everything looked good. Float level was also adjusted properly. When pulling the choke out, the bike bogs down even more compared to when the choke is in. In order to start my bike, I need to give gas for about 20 seconds until the engine is fully warmed. I never had this issue before. It could be a deeper issue than I think...

[@dirtniron]

sorry for late response. I would take the carb out, clean and inspect everything, then get stock jets or JD jetting and start the tuning from there

[@fynn8252]

@@dirtniron hey no problem! I appreciate you reaching out still. It ended up being a misadjusted intake valve from the prior owner! Bike is all fixed and runs amazing! 😃 BTW: I left another comment on your 5 reasons you like the WR450 video.

[@Thornicide]

I have an 06 WR450f and its backfiring just like yours was, Is this what is causing my bike to overheat very quickly? (I discovered my fuel mixture screw is missing and ordered a replacement.)

[@TheSilentboy1980]

👏👏👏

[@colbymiller485]

Hey do you think I it's leaking out of this screw the oring is bad

[@eliasmarkiet4180]

Thank you so much! Could I install this with the carb still in the bike?

[@dirtniron]

you can try to rotate the carb until you have enough room to take it out, watch out for spring, washer and O-ring

[@danielgeorgsson8556]

best video

[@dirtniron]

thanks, glad you like it!

[@gixxer7907]

The idle was highest at 2 1/4 turns out from seated so have ordered a bigger pilot jet

[@catocoman]

Really nice video. One question. What kind of battery do you have. How many cca amph does it have to start the bike so easily?

[@dirtniron]

not sure exactly, it was lithium battery

[@swoogles4093]

My 04 CRF250R runs well but sometimes going down hills with throttle closed it backfires and then stalls when clutch in. Choke on fires right back up, I'm thinking of buying one of these so I can adjust it on the go.

[@dirtniron]

yea, you need one for sure

[@archiekruze7421]

Anyone know what the black screw on the carbureator on a kx250f 2005 is?

[@butterbean2523]

Which direction would you adjust the screw for an increase in elevation or temperature?

[@dannionconrad6717]

Two years late, but as the air becomes thinner you need less gas to compensate

[@Hondacrf2024]

What is the black octagon screw above the air fuel screw you turned and where does that need to be set

[@dirtniron]

that is idle adjustment, you need to play with it little bit. once you have your fuel screw set and have good throttle response, use the black screw to lower or raise your idle

[@krafczyk1927]

Maybe some one knows what size orings i should put there?

[@GuillermoDelBosto]

do someone know the size of that little ring ?

[@stu0700]

I found the Fuel Screw on JD Jetting website... Do you know where I can find the Idle screw as seen in the video as well?

[@dirtniron]

i am not sure, I thought it already comes with it

[@marcorubio5122]

That black bumpy knob on the thumbnail, is that the idle adjuster?

[@dirtniron]

yes thats right

[@leafywatson249]

Sorry it has a auto start and a kick start also thanks for your videos

[@dirtniron]

Cool, glad you figured it out. Good luck man!

[@woogied2]

How come you went with the WR over the YZ450F.

[@dirtniron]

I got it on trade, wanted to check the bike out, especially wide ratio gearbox

[@segurahh1179]

Hi, I'm a newbie in motorcycle mechanics and have a doubt. Clockwise in air screw (turn it "in") mean more air or less air / lean or rich?

[@dirtniron]

air screw - in means less air out means more air fuel screw - in means less fuel out means more fuel usually 2 strokes have air screw and 4 strokes have fuel screw, so they work the opposite way.

[@azm1azm1azm1]

On a 03 KTM 450 after complete top end rebuild , cylinder re sleeve, new piston & new titanium valves and new adjustable accelerator pump with every thing tuned and running perfect. one day after a few months my muffler started melting my side plastic muffler cover, then a few days later the bike starts to lose power at higher RPM. Any ideas ? Thanks for any help on this. Carb is KEIHIN FCR-MX 39 Carb jets stock 170-40, in shop book 175-48 Jets In as of 03-22 - 178/50

[@jacobponce9900]

I have an 04 KTM 450exc. It sounds like you're running lean, you need more fuel or less air. Ideally, more fuel. To verify, try running the bike on the choke (less air). If it runs stronger, that's a confirmation.

[@jake_hull_offical]

What cani do if my o ring and washer dont come out with the old one?

[@dirtniron]

put the screw back and try to take it out again.. you need them.. maybe have to take the carb apart ...

[@leafywatson249]

Hi dirt n iron im really upset please help me I brought a used 2013 250 ssr and I lost the two keys that came with it what can I do about it

[@dakotapicklesimer1554]

Leafy Watson by a new ignition switch off eBay with the same wires for easy plug and play installation

[@livingthedream4882]

Quick question mate...I got a new 250 4 stroke brand new...when i start it and put throttle it cuts out do I screw the screw in on the carb or out...thanks

[@dirtniron]

if its brand new its probably fuel injected.. does it have carb? you need more fuel if its cutting out, so you need to go out if you are talking about a fuel screw

[@livingthedream4882]

@@dirtniron yeah it as got a carb mate

[@livingthedream4882]

@@dirtniron when I pull the throttle slowly it revs up but when I rip it back fast it stalls out

[@dirtniron]

@@livingthedream4882 sounds like she is too lean, bogging when you go on the gas fast. Give her more fuel, maybe need even bigger pilot jet. try first to adjust fuel screw 1-2 turns out

[@livingthedream4882]

@@dirtniron thanks pal for getting bk in touch...I will have a look at her 2moz ...I will let u know how I get on 👍

[@bikelifesoldier5412]

I just received this screw as part of a carb rebuild kit. Everything went as it should until I check my throttle cables at the carb. If I open the throttle completely it locks itself wide open. The screw next to the wheel/pulley that the cables hook into inside the carb clicks at full throttle and wedges itself against the wheel. Please help I've tried everything!!

[@dirtniron]

you have to fix it, take it out and inspect .. something is wrong

[@bikelifesoldier5412]

@@dirtniron thank you for taking the time to respond. I eventually realized (after 3 days) that I was not reinserting the pulley cover screw. This screw serves two purposes. One being to hold the pulley cover in place and two stopping my pulley from turning past full throttle. If I had put it back together it would have solved the problem but I wouldn't have known why and I'm trying to learn shit! 👊✌

[@joshuadixon7395]

Question. I just did my first 05 ktm 450sx rebuild and it starts and idles clean but when I give it throttle it cuts out and runs like ass. Could this be a jetting issue?

[@dirtniron]

Yes it could be the carb. If it cuts out under the load it sounds like its too lean. Try one size bigger pilot.

[@matthewsmith5109]

Could be mid body orings, they don't come with carb rebuild kit, you have to order mid body oring kit from all balls. The stock o rings deteriate and clog the orifices. Kit is 16 bucks.

[@gixxer7907]

I bought a fuel screw for my ktm 450. I tried it today but the fuel screw keeps loosening when under full throttle even when the fuel screw is one turn from seated. I took the fuel screw out and noticed the o ring wasn't on it but was seated in the carb so picked it out with a paperclip. Will that have been why it was coming loose? Or any ideas as to why it is coming loose as the vibration under full throttle is just undoing the fuel screw

[@dirtniron]

oring was in the right position, seems like.. they tend to stay in the carb when the fuel screw is removed. it should have oring, washer and the spring. do you have all 3?

[@gixxer7907]

@@dirtniron yes, it is a new fuel screw. I had washer then spring then washer then o ring. My old fuel screw the o ring snapped so just bought a new fuel screw but this one keeps coming loose where as my old one didn't but I had no washers with my old one and the new ones washers are slightly too small to fit so I can't fit my old one. I guess I'll just have to put it back together and hope for the best 🤷🏻‍♂️ if it still loosens maybe try loc tite on the threads?

[@dirtniron]

@@gixxer7907 I dont think there need to be 2 washers, spring, washer, oring.. thats the way I installed it.. what brand did you get? jd jetting has good product

[@gixxer7907]

@@dirtniron I got rfx. Some do come with two washers but not necessary. Thank you for replying and wish me luck lol

[@Dupray__]

Does this also help with throttle response?

[@dirtniron]

sure does, once you have your bike dialed it runs better

[@nouri792]

help i switched from 2 stroke to 4 stroke and only noticed that it has no oil tank .. 🤦‍♂️ i was looking for the adjusting screw for a while, but then it didn't have any until it always died at full throttle, whether the screw was in the middle , all in, or almost completely out. I noticed the screw later because I saw that it wasn't in vain. it has to be a mix even if the 4-stroke only burns gasoline. what do i have to do as a german i can't find any german videos it's so hard to understand. how much does it have to go in and how many times it has to go out again? 1.5-2.5? I ran at half throttle for 10 minutes, did I destroy the engine? I need an answer quickly

[@dirtniron]

it depends on your jetting, usually around 2 turns out is ok

[@jiggydogg14]

I just got a yamamha ttr 125 and it idles super high and it gets super hot within 3 seconds of it being started what can I do about it

[@dirtniron]

adjust the carb, check the throttle cable make sure you have little play on your cable..

[@jiggydogg14]

@@dirtniron ill try that thanks

[@miguelmartov7951]

My motorcycle is Yamaha yz 250F 2003, already hot it does not start or using the lever above the clutch, what can it be?

[@dirtniron]

too rich maybe, when did you check valves last time?

[@miguelmartov7951]

Dirt N Maximum is 5 months old, and from that time I have gone out 8 times to the bush, I changed new valves, gaskets, calibration chips, piston rings, I only did nothing to the carburetor

[@andreig8895]

What can i do if my fuel screw is lose? If I tighten him he has no problem, but if i unscrew it, he will fall from vibrations. Can I use it or buy another one?

[@dirtniron]

Needs to have the spring to keep the pressure. Maybe you need to get new one, but make sure it has a spring.

[@noahsteffens828]

@@dirtniron For some reason my fuel screw won't go all the way in. It seems to be the spring holding it up because it slides in just fine when I try without the spring.

[@suriyanarayanan5222]

Sir, why does my bike engine off while i applying the choke?. Is it running in rich or lean ? please rply

[@dirtniron]

rich

[@suriyanarayanan5222]

@@dirtniron my yamaha 125 cc bike starts in one kick,but the rpm slowly down with in few sec, i increased the rpm also but the engine sound is rised. I can't fix the idle rpm in normal .plez reply.

[@suriyanarayanan5222]

What is the idle rpm of my yamaha 125 cc bike? It wants more rpm to stable, normal rpm was not starts the engine after 2 hours the shutt of engine.reply plez.

[@aleajactaest4975]

Hello my friend and kind regards from Hellas (Greece) island Cyprus.. I have one ATV YFZ450 model 2009 and i don't know how to adjustment the carburettor.. Can you help me please.? Thank you..

[@dirtniron]

get correct jets, maybe start with the stock jets and needle first. Clean the carb, make sure its all clean and then see how she runs, play with the air screw and see if you can adjust it to have crisp response. Check my "how to adjust idle on 4 stroke dirt bike" video for more tips

[@aleajactaest4975]

@@dirtniron Thank you my friend but I do it that 😅 My needle screw is 6 around back, is that normal.??

[@boneyguy1]

I turn it to two turns and it still pops and wants to die, I went to 2.5, and 3 turns as well. Doesn’t seem like it’s getting enough gas still

[@dirtniron]

try bigger pilot jet

[@marcinyamaha5986]

Czy ktoś może mi. Powiedzieć ile obrotów dal ?

[@Zen-525]

my fuel screw is real easy to turn. can it fall out?

[@dirtniron]

yea it can.. do you have the spring? maybe get new spring

[@ramseypaulpierre8231]

I m having the same freaking issue with my

[@frankiemarchese2978]

Do you know the sizes of all your jets?

[@dirtniron]

Pilot 45, main 168, rest should be stock..

[@frankiemarchese2978]

Okay cool just asked because when i recently took my carb off i noticed the pilot jet was huge. Stock is 45 and theres a 58 in it now. The starter jet is smaller than stock I believe and the main is stock. No running issues and the fuel screw is about 1.5-2 turns out so i guess its all good

[@dirtniron]

58 is really big, I never heard about such big pilot in WR. I had 50 before, with different needle, but now with JD jetting needle 45 feels great.

[@frankiemarchese2978]

Yeah i dont think it needs to be that big even though it has a full fmf. Ill turn the fuel screw down to 1/2 turn out and see if it runs like crap. If nothing changes ill go down a couple sizes on the pilot.

[@beginnerrider6681]

Can somebody out there please help I know this video is old but I have the same carburetor but mine's has a Welch plug over the pilot air screw and I removed it and put a new one in and now the bike doesn't want to start it just kicks over

[@dirtniron]

you put an aftermarket screw in? make sure you adjust it same way it was before, or play with it until it feels the best

[@beginnerrider6681]

Dirt N Iron thanks so much for replying to my question I didn't think you were going to reply to be honest but anyway yeah I have a 2006 Yamaha TTR 90E and, is a Mikuni carburetor in the mixture screw is so hard to get to I will have to take the airbox off so I can't really do a diagnostic so again I'm glad that you told me to get one of those aftermarket screws

[@Brensta18]

Mines so loose it’ll rattle out. And the spring is in it so idk what’s wrong

[@dirtniron]

they get loose if they are turn too far out, if you need more than 3 turns, then try to go with bigger pilot or lift the needle one notch.

[@azlong4596]

Rado get a wrench in that girls hands and up on a bike. No better time than now to get her MotoVated.

[@dirtniron]

Haha, that's great suggestion. She likes to hang out with me in the garage. :)