How to jet your Dirtbike Carburetor CRF450 CRF250 CR250 CR125

Amazon sells jetting kits. Get one HERE→www.amazon.com/gp/product/B002...
Yes I know my cinematography sucks, but I've had so many requests for this I figure whipping this video up/out would be better than nothing at all. A wise man once said that sometimes perfection robs creation from happening. Git'R DONE! lol Oh well, here you go- How to jet your Honda Dirtbike CRF450 CRF250 CR250 CR125

[@briansmobile1]

Yes. Your airscrew will have to be adjusted regularly if you have seasonal temp changes and you need it to idle in traffic. You can buy an aftermarket one with four numbers on it and a long knob to make it easy.

[@TheSusanrudolph]

You are a great teacher and have helped me to understand the fuel/air system. Thanks for posting these videos, very helpful. Please keep it up!

[@michaelromrell4791]

Thanks for doing this video. the explanation of each jet/needle/screw and their locations was super helpful!

[@91lxstang]

I have came across 3 of your videos searching for completely different things throughout this week! good video man!

[@XEdzel]

You're videos have so much useful information! Thank you for your time in making them.

[@Sweloe]

Hey man I seriously appreciate your help. Keep it up!

[@EPstroker]

Thanks for the vid learned a lot. I have a crf 450x that's doing the popping thing and very lean (header pipe starts to glow when I fire it up after I opened up the air box). I did the air box mod to it. And need to re jet, not sure what I need though. Right now the needle is in 3rd position, and jets are a 150, and 60s. Air screw is 2 and a quarter turns out. I just bought the bike and am trying to get it sorted out. I'm in the south east and elevation is around 500 above sea level.

[@YearRoundFails]

THANK YOU SO MUCH! So informative. I've been looking all over for a video like this. Thanks so much!!!!!

[@yeahwerepthesamesmartech7113]

pretty damn good video explaination for no sleep. give this guy breakfast and no telling what can happen!

[@fdx723]

cheers Brian helped me out alot very detailed and well put together!

[@nathanealmatlack3960]

You just earned a subscription. Thank you for this video it was very informative. Keep up the good work I would love to see more.

[@sidpineapple]

hey man. thanks for the video. my 09 Crf250r has a misfire when I hold the throttle steady- like cruising up a road or something (around 1/2 throttle) it doesn't have any bog or issues anywhere else through the throttle range, got some advice for me?

[@willc44]

hi @brian my 2007 CRF 450X is kinda hard to start and has a huge flat spot in the throttle when exiting corners and throttle delays a lot at low RPM too (like on single track) alot of poping & blubber in deceleration. 170 main 45 slow jet. I moved the needle up from 4th to 3rd. U think I should go down on the main as well. I also backed the pilot screw about 1 1/2 turns I live in northern California THX Bro. :-)

[@briansmobile1]

@DWOODY12 You want to jet it at the temp you plan to ride at. Temp and altitude both play huge rolls. Humidity can also play a role as well.

[@winkscrf150]

nice vid man i like the sound effects "pop-poppop-popopopop" haha nice

[@briansmobile1]

@MegaDogslayer With it being winter that's common due to the cold. I'd run it till it's warmed up for sure on the choke. Also if it's been sitting the gas may be bad. The popping is from being too lean and the choke requirement is from being too lean as well. When it's cold out you have to run richer because cold air is more dense and basically thicker so it makes it lean.

[@briansmobile1]

@DWOODY12 How long since it's had a tune up?

[@briansmobile1]

@DWOODY12 That's normal because you're going from high RPMs and then cutting fuel real quick so the mid-low jet is dealing with high vacuum pressure etc and a small port. As for the cold mornings you can adjust your air screw to improve starting or twist the throttle five or six times before starting.

[@qwerty123627]

hi brian i just bought a kx250 2t and the thing is running really rich and idleing high if i start it up the pipe instantly drips spooge theres a constant drip and the bike is smoking a fair bit just wondering what you think possibly just jetted wrong and the spooge is smoking or crank seal leaking?

[@gabrielthompson1072]

Nice video, I use to do this my Yamaha years ago. Have you checked out Lectron carbs?

[@briansmobile1]

@kayvonmansouri When you're on the road racing you'll re-jet three or four times in a week end to be in peak performance if it's a new track/elevation/humidity to you. Then you write down what worked and what the conditions are/were so you can short cut in the future. If you just want a close enough setting you can get an aftermarket air screw that can be adjusted by hand and only address it on that circuit where it's often most noticed.

[@briansmobile1]

@Shroffff YES if you run too lean you will overheat. On a race bike you want to be a little too lean because of the power you get, but it's really hard on them it makes them burn up prematurely. Any time you see an engine failure in a race it's almost always due to being jetted too lean.

[@jasonnichols9809]

I've seen a few videos you've done to work on my silverado. I just searched for this thread and as i was watching the intro for this video i knew that voice was familiar. sure enough I was right. I didnt know you work on dirtbikes also. Great videos man. Keep them coming. I'm in Phoenix, AZ elevation is just over 1000 ft. Riding an 04 cr250. summer's coming up so 90's-100's i will be riding in. should i run mine at the second notch? also what size for the bottom needles? thanks in advance

[@mundanus84imperium]

Hi! I watched your video a year ago and still watching it trying to figured it out how to re jetting my bike. I have a crf 250 r 2006 and it was on my garage for two years now without use. The last time i rode it, the bike was lean i guess with the (pa pa pa thing while de accelerating). So i re shim and clean the jets founding two clogged. I ran the bike for some minutes but the pipe it's getting red hot glowing and the bike are unstable it goes off as soon as i let the throttle off. The jet sizes are 55,40,68 and 172 main. I'm at sea level between77 and 90 *F. I hope you can help me out with the jetting thing and also want to know if you exactly know why the pipe get so hot. Do you think the jet sizes are ok? The glowing thing obey to a lean mixture? Cool video man and thanks in advance.

[@briansmobile1]

@oishisakana You're welcome. I'm glad I could help you. I like grateful people!

[@briansmobile1]

@ML424wr Leaner means less gas. Thinner air is less air so you jet less gas to maintain the 14.7 to 1 stoichiometric balance that makes the bike funner.

[@goonvids1]

do you know the jetting of a 125 cr 05 with pro circuit pipe & R304 ? my spark is full of oil every time i do low rev

[@briansmobile1]

@kayvonmansouri This year is dry enough that you can still ride, but it's still cold too. It's likely your air screw adjustment is set too lean. Just like you have to choke the bike to start it cold so it's riched up- when you ride in the cold you have to have it richer.

[@briansmobile1]

Thanks for the feedback- you're right. I'll get one.

[@bristol32distraction]

I love your videos, and this one in particular helped me tune the carb for my 2006 honda CRF450X. I had a question for you. Is it possible to add an electronic ignition kit to this bike? What is involved, and where can i buy it? Thanks again, and keep the videos coming.

[@Shroffff]

another great vid thanks man :) and i am loving these sound effects keep them coming :) but one question, is running lean a large problem for over heating what ?

[@crf450rjaybird3]

hello i just installed a stage 2 hot cam & jebco exhaust the bike runs good no poping but its stock jetting should i up jett? its a crf450r 2005 thanks for your time

[@uva3617]

hello I have a 2003 crf450 I live in 5000 ft whats my best way jet it right and also I just put new piston and valve but I stared like 3 time oil seen clear looking the I left to re adjust my valve an the oil was milky but no white smoke

[@briansmobile1]

@blairaudio  The pilot jet and main jet are different like the on-ramp and the freeway are different.

[@jamiemanley1579]

So my elevation for where I live is around 3000 i am running a complete fmf system and my main is currently a 170 and my slow jet is a 40 what should i change

[@briansmobile1]

@turboz8826 The idle is that knob on the left side of the carb that you can turn by hand, but sometimes has a flat screw slot in it. NOTE- only set the idle after the bike is warmed up or you'll stall in the corners or in the air.

[@McDoobles]

Beauty video bud, BAM!

[@briansmobile1]

@ihavetwonipples That pilot screw is the adjustment for the starting circuit. It needs to be backed out a bit more.

[@tescoireland1234]

Great video brian. Can you make a video about carb sync please?

[@briansmobile1]

@bsavage14 Try one setter richer (higher number) on the jet circuit (throttle position) that causes the symptoms Usually mid to main jet.

[@jamesv2811]

Thanks mate this saved me allot of time

[@ihavetwonipples]

@briansmobile1 Lake Tahoe CA, I'll take a look at what jets are installed this weekend. what about the little screw on the bottom of carb... if I twist that would it help to start the bike?

[@mustangmike04gt46]

great video man.

[@pablobasstb]

your explanations are awesome!

[@arjunpamidi]

I have a ssr 70 c pit bike and When I throttle it too hard from a low rev, it goes phut phut phut phut phut phut , wat do I do

[@urmomsayswhat]

what would you say if the bike pops, takes gas pretty well, but runs better in cooler weather, likes the hotstart when fully warm and it's hot out and if I'm sort of crusing on a big trail it seems to like about 1/4 throttle? oh but it pops when I'm decelerating down hill. I think it's running rich?

[@kayvonmansouri]

Hey Brian Great vid thanks for posting. I'm a fellow Utah'n (Salt Lake area). My bike (2005 CRF450R) runs really strong but recently started poping on decel and wants to kill (lean like you describe). Its never done it before until this year. Have you seen a dirty carb do this? I realize that jetting may be the answer, but where its never done it, I wonder if it has a clogged jet. Also have you seen the hot start stick to cause this? i removed the cable and pushed it in, still does it.

[@HairyCarpet1]

can you be to rich on the main jet and to lean on the slow. when im at low speeds and let of the throttle my bike pops. and sometimes when im at highspeeds and i get on the power out of a turn it blubbers a little bit and almost cuts out for a second

[@bulmer69JR]

it is summer time what jet should i run it is very hot could i just adjust the fuel air what jets would you run to stop the blubbering?

[@kayvonmansouri]

@briansmobile1 . So do you just keep your jetting the same and adjust your air screw from winter to summer in Utah? Also are Hondas more prone to this? My riding buddies dont seem to have the same problem. I realize it could be other factors. Thanks again for the reply

[@honda06cr125]

I have a cr 125 and I put a pro circuit full system on it and I have a jd jetting kit in it should I change the jetting or not

[@briansmobile1]

@turboz8826 Focus on one circuit at a time. Remember jetting is like playing battle ship. You have to stab in the dark some times to find where you need to be. Also if your goal is to make it idle make sure you're getting it up to operating temp before moving on.

[@tuckerbessinger8003]

I have a 2006 crf250r and my elevation is 354 what jet do I need to use and it is about 80 degrees out side

[@briansmobile1]

@ferebeescott211 It's your air screw and slow jet. (usually a #42 stock you need one leaner like a #40 or #38)

[@the934x4]

My bike bogs a little on pick up until on the pipe, but also does the lean popping when cruising at 1/2 to 3/4 throttle, like on the road between riding spots...on the pipe it's fine and down low it's bogtastic-suggestions? 02 CR125

[@yonmoore]

What do I do if it's hot as hell outside and I'm 100ft above sea level? I'm in Houston. Any recommendations? Thanks for the vid. Good job.

[@Shroffff]

@briansmobile1 ah right thanks but how does too lean lead to more power ? less drag in cylinders?

[@briansmobile1]

Thanks Nate!

[@ares1180]

Hey Brian can a sticking hotstart lever cause the bike to pop and run lean???

[@topsecret6970]

Brian i am havin some issues with figuring out what to do to my carb. i have an 05 crf450r stock except for jardine rt-5 full system. bogs reall bad when going slow then dumping on the gas or when going threw woops or hitting a hill at a decent speed. which most would say its rich. but the spark plug tells me its lean as hell. it also does not idle well untill warm. What to do!

[@FalcoGFX]

I'm trying to get my carb tuned up perfect on my 0'2 cr125 two stroke because when I give it sudden throttle right now, it bogs down alot. But I'm not really sure what that means, do I need bigger jets or what? Can you tell me everything I gotta do to get that crisp throttle response?

[@ferebeescott211]

When you come out of a slow corner and you twist the throttle wide open, while the bike is still at a low rpm yet the throttle has been completely opened what curcuit is it pulling off of at the moment? My CR125 runs its ass off at wide open (after it burns the excess fuel) but feels like its pulling a led sled when beggining to accelerate until it burns off the extra fuel

[@ridemx787]

@creepy4valentine the power valve is most likely stuck. i used to have the same problem on my rm125. if that happened while i was out riding i would just find a jump i could flat land and just land as hard as i could and it would free it up

[@briansmobile1]

@MRPITBIKEMASTER Most techs that are pros and tune for guys like James Stewart or Andrew Short have to do it a few times each race. It's only hard the first time then it gets easier.

[@MegaDogslayer]

Great video. I've read through all the comments. I've got a question also. I just bought the bike (2004 CRF450F) Previous owner put a White Bros exhaust header and silencer on, and said he never got around to jetting it. Only idles with the choke. If i kill the choke it will kill the bike. I also get a lot of popping from the pipe as well. If i want to ride the bike I have to keep the choke on or it will die when i let off the gas. Where would you recoment I start?

[@paintslinger2009]

I have a 125cc Loncin i had put a new air filter on it And cleaned the carb properly but I have a different style air box with very little resistance so will that make me bog when I punch it over 3/4 throttle not enoughair flux to pull the gasout the carb properly is my guess it ran full speed before any opinions please thanks I also tryed numerous carb settings like add more fuel it pops add less it's also shit

[@Evilstone222]

Looking what do you think jets wise ik I should get to jist test jets wise

[@mastahermit]

g-day Brian.. i was a little worried about re-jeting my carb xv1600 roadstar, just installed a kuryakin hypercharger....... thought it would still run without re-jeting but my scooter was one sick puppy. your vid was just what i needed, loved the white board and you pointed out a few simple things. not so worried now as i can only break it....? not sure if you know the bike but if you have any more jewels you care to share......?

[@hepting9]

This is a great video! I have a 2006 CRF450x. My bike has been overheating, especially at low speeds (I can hear the radiator boiling). After some research, I'm thinking of trying to change the jetting. I pulled the spark plug tonight and it appears like the bike is running too lean (which makes sense as I pop a lot as well). Can you tell me where I should start with the jetting? What do I ask for at my dealership? Do I need to change out all of the jets. Any help would be appreciated..

[@briansmobile1]

@MRPITBIKEMASTER Keep your 42 it almost NEVER needs adjustment. Try changing TWO MAX. ONE at a time is better I'd start with the air screw. (most likely culprit) and then jet needle.

[@428428428428]

Hey Brian, I have a 2003 crf450r and the bike runs great but lately i have been having an idle issue. The bike doesnt bog down and runs good but once it is hot and i stop it dies, it doesnt want to idle at lower rpms. I have played with the Pilot/air screw but it doesnt seem to help much. Im going up to the mountains next weekend to ride and dont want to be kicking the bike every time i stop. what should i do/adjust. Thanks, Nate

[@briansmobile1]

@indosurfer210 You're welcome- I appreciate the feedback that it helped you. It makes me feel like I'm making a productive difference with the vids. I usually just get a pile of questions.

[@stix746]

What size jet u think I should use on a crf 450r with 40 over piston in it?

[@briansmobile1]

@MRPITBIKEMASTER Try it and see what it does. To get it right on you'll most likely make more than three adjustments. Especially when just getting into it.

[@briansmobile1]

@ihavetwonipples You're too rich on your main jet and too lean on your starting circuit. Are you in Colorado or Alberta?

[@bulmer69JR]

hey brian i have an 04 crf 250 r it blubbers or pops at mid throdle it ok when im on the throdle the wheather here is 85-90 with high humidity i have a 152 main jet ,a 40 slow jet ,3rd clip on the needle oh great trick on snapin the throdle to get it out.and the fuel air screw is 2and a half out im in canada at sea level. it also loses power on sandy hill then want to die im thinkin im to lean what would be the correct jetting thanks ED

[@DennisRawet]

Ive got the problem on my CRF250R -09 that when its cold it almost dies, have to adjust the idle screw up a bit untill its good, after 2 laps on the track i have to re-adjust the idle screw down, cause the idle is so frikking high ppl think i run with full throttle almost.. is something clogged? have to post this on some forums maybe to get better help.. thanks for a good video!

[@briansmobile1]

clean the carburetor bore etc. AND likely address a throttle tube issue.

[@briansmobile1]

@creepy4valentine I'm half Swedish- check the silencer for blockage.

[@briansmobile1]

@HWeingard You're welcome. Thanks for watching it.

[@ares1180]

Brian Help me out Please? Bought a 2002 crf450 thats popping. It runs great.. it just pops. Pulled the plug.. snow white. Took out the jets from the carb and they are clogged. So im guessing its running lean right? Cleaned the jets put in the new plug and took apart the hot start lever because I think it was letting in unwanted air. Lubed the cable and it looks good now. I started the bike and definetly saw an improvement but it still pops mostly when i let off the gas. Im stumped what to do??

[@drakewall8475]

Brian please help my four stoke was popping so I moved the clip on the throttle down one I started the bike and it revved so high i was bout to blow the motor is it the throttle cable?? Can you please help??

[@Daniel96sj]

Hey need your help please. I bought a 1996 YZ250 and its having alot of problems but runs, so I decided to rebuild it. Anyway what do you think will be wrong with my carb: My bike starts fine when its cold, but once its warmed up after ridng and your turn it off you cannot start it again, the only way I started it was by push starting it. Also once its warmed up it idles really high and when its in gear it keeps going without any throttle. Ive bought a new top end and clutch plates

[@ihavetwonipples]

crf450,low hours, with FMF exhaust, high altitude 6200 ft+, usually cold temperatures 50'-, FMF jet kit installed to recommended settings, bike is very hard to start when cold. At running temp fires right up. Hesitates when full throttle (wide open) is applied. Do you have any thoughts, ideas, jet/setting i should run? Or should I just send you the bike to dial in....? Pretty nice vid by the way.

[@jamesrussell4914]

I rejected my bike no hezitation wen I hit the throttle no hezitation but under declaration it pops and back fires and spits flames is that normal or what

[@buddyofplumphy]

i have a crf250r it sounds flooded when starting and it wont hardly start when cold i can roll start it and it backfires when i let out of the throttle after it gets hot you can kick start it and when you shut it off it makes a gurggiling sound i need help

[@melaniemartinez5180]

so on my cr125 my bike runs rich and i run a 40:1 ratio on my fuel can u help plzzzz

[@danmickelson1109]

Great video! Thanks for the help.

[@zmancrf150r1]

I have a CRF150R and it pops when i let go of the throttle, So it is too lean. What size should i get then if i live in Kansas

[@Colombiaenduro]

hi briansmobile1! i have a big problem with my honda crf250r 2005 starting it up cold! i kick it a ton of times and it sometimes starts but then dies off. Eventually it starts but is very hard to get running. once running the idle is a bit high when the clutch is pulled in but once i let go of the clutch the idle goes down to normal yet the bike moves a bit by itself. If i give it quick gas the bike bogs down and almost dies. I have to accelerate smooth and precise from standstill. what do i do

[@natew6115]

i NEED your help man. i live in so cal around 1000 to 2000 altitude i have a 2007 crf250r i bought the bike with the t4 dual pro circuit slip ons. but i have a hug amount of pop like your talkin about when its to lean so i checked the jets... i have a 175 main in rite now and a 48 pilot. so i upped it to a 180 main and a changed he pilot to a 45. an that didnt help i still have alot of pop what would u suggest????

[@briansmobile1]

@FutabaKIKS It ALL depends on how open the throttle is when it backfires. (White board diagram at 4:08)

[@georgevreeland5569]

hey, i have an '05 YZ 250f, i just had top end rebuilt, carb cleaned and a new main jet, i have 3 rides on it since i got it back, i was going to sell it to my boys friend, i tried starting it and it ran like crap, a friend of mine is looking at it, he told me that it needs a vacuum tube, how can it run perfect one ride then run like crap the next time u start it ?

[@briansmobile1]

@FutabaKIKS Yes. Or your timing chain is off a tooth or two.

[@briansmobile1]

@DWOODY12 Flames can come from a lean backfire. Too rich usually will blubber and lack power.

[@ThePro1807]

will jetting your crf250r elimanate the bog? someome please answer

[@refns2005]

What do i need to do if the bike keeps pulling after i let off the throttle?

[@MrNyad1346]

hello dude perfect video !! my yz450f works good but when i give gas some times my idle are higher and after 5-10 secs goes to normal !! maybe u can imagin the reason?

[@PQR5CHE]

bio shout that means your to lean

[@topsecret6970]

and to top it all off i was trying to incorporate a dynojet jetkit but that makes it more confusing because the main jets they give are way smallar then what is in it now

[@FutabaKIKS]

@briansmobile1 Oh great. Does this mean I have to get new jets, or just adjust that needle?