👨‍🔧 Tips Adjusting Air Pilot Mixture Screw Mikuni Keihin Carburetor 2 Stroke Dirtbike MX YZ250 KX250

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These are just general guideline / tips. You should check this adjustment for every ride (even during the day of riding.) If your bike has severe running issues - this will likely NOT resolve that problem. Before you go diving into your carb and turning your air fuel mixture screw - make sure ALL services and maintenance are up to date - and that there are no OBVIOUS issues that need addressing. This video demonstrates what you should listen for when adjusting your air pilot screw. And the difference in sounding Lean and sounding Rich at idle. Make sure your carb / carburetor is clean and rebuilt with no obvious problems. Make sure your crank seals are good. Make sure your exhaust silencer is clean and repacked. Make sure your intake reeds are in good condition. Make sure there are no intake leaks, exhaust leaks, or other obvious crankcase leaks, etc. Make sure your topend is recent. If you have other questions, please comment below.
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22 авг 2024

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Комментарии : 99

@auskilluminati333 2 года назад

Simple and effective video. What's missing on RU-vid nowadays 👍

@HorsepowerHouse 2 года назад

got tons more on our channel

@sergiogutierrez9184 3 месяца назад

I agree

@freetaylor72 Год назад

Great video man, whare I look when it sputters when I get on it about first 0 to 1/4 throttle. Seems like when I hit 3rd she blasts off like a rock, but until then she hesitates alittle. I installed the JD jetting kit the way they showed it. Sunk alot of money into this build...my first 2 stroke

@HorsepowerHouse Год назад

Throwing a carb kit at it is probably not the fix. You have to make sure all services are up-to-date including: thoroughly cleaned and inspected carburetor, top-end, air filter, exhaust silencer packing, all O-rings relating to the exhaust, carburetor and intake, inspect intake reeds for damage, check cylinder compression, do a spark plug reading, etc. We need to know what year make model and how many hours are on your bike before we can recommend anything else. My guess is a thorough service and maintenance of your engine and carburetor are in order... Stock carburetor settings are fine for most bikes unless you live in extreme altitude, or at sea level in high humidity (or the above services are not up to date ..) Post a long video of you riding your bike and of the bike running and idling and will we advise you further.

@freetaylor72 Год назад

@@HorsepowerHouse Yes will do... I've done everything you mentioned except repacked the silencer. But I will post a video for ya and I really wanna say thanks for your time. I'm pretty sure it just needs a fine tuning, but like I said I've just been learning as I go. The bike is a 01 ktm 200 mxc, compression is 165 out of 180 on a new top end... new Keihn 38mm carb with the jd jetting kit. New air filter, reeds, spark plug etc....crank seal water pump seal.... . 50/1 gas mix with high end race oil.. bike is a monster... I'll shoot a video this weekend so you guys can help out! Thanks again

@HorsepowerHouse Год назад

@@freetaylor72 Has it always had this problem, or did it just start doing it? And definitely check the silencer packing and exhaust o-rings. Where do you live? (Altitude & climate) Post a video and that might tell us more.... -Dave

@HorsepowerHouse Год назад

@@freetaylor72 What is your jetting? Pilot, Main, Needle, Air Screw setting etc....And what fuel & premix oil do you use? And how does the spark plug look?

@HorsepowerHouse Год назад

what did you determine?

@enforcedraccoon8648 3 года назад

Will warmer weather create a more rich or lean condition?

@HorsepowerHouse 3 года назад

For most summer weather, also means more humid conditions as well, so that is "dirty" air (with less oxygen) compared to much "cleaner" drier, denser air in the winter. So, you should equal that with fuel flow as well. If the bike is "breathing" cool, clean, dense air, the bike usually needs more fuel (otherwise the bike the will run too lean). On the other hand - If the bike is breathing hot, humid "dirty" less oxygen air - it needs "less fuel" to have the perfect air/fuel ratio. So, simply put, bike needs leaner carb settings in hot summer, but richer carb setting in winter. Of course it depends on where you live, altitude, humidity, etc. Go on how the bike is running though - how it feels - as well as a spark plug reading.

@enforcedraccoon8648 3 года назад

@@HorsepowerHouse ok thank you

@M3vibe92 Год назад

@@HorsepowerHouse Thank you!

@horizonview1850 Год назад

Best indepth video ever

@HorsepowerHouse Год назад

Got lots more on the channel.

@morganhay859 2 года назад

Mine pops off for a second and then shuts off. I’m thinking some sort of carb adjustment. Takes a couple kicks to get it started after that

@HorsepowerHouse 2 года назад

As stated in the Descriptiopn - fully service, dissassemble, clean, rebuild your carburetor - IF everything else has been serviced. Top-end rebuild, petcock cleaning, fresh fuel, new spark plug, etc etc etc...

@HorsepowerHouse 2 года назад

What you are describing could be caused by a million things.

@jonny621 2 года назад

i have a similar problem on my honda cr 250 carb mikuni tmx 38 ... i already replaced all parts pj 25(40), mj410(420) , needle jet s7, needle gdy26-68(gdy26-65) float level 10(7.5) , doesn't want to idle. I have 3 revolutions of air, but it still seems to have little air and reacts badly to the air screw, can I take it all out to increase the idle speed....could it be a problem with vforce3? they are about a year old, I had them outside and I didn't see a mistake

@HorsepowerHouse 2 года назад

Has it always had this problem? Or what started it?

@jonny621 Год назад

@@HorsepowerHouse no, and I don't know how it started, I just noticed that it was still smoking,I already had it cleaned with an ultrasound and it didn't help, but now I took it apart over the weekend and cleaned all, even the smallest channels, with a wire, but now I have the problem again that I'm probably low on fuel, because when I step on the gas, it keeps a high idle for a while and after it drops in a few seconds, so I go up with the idling nozzle, now I put 30 but it's still not ok

@HorsepowerHouse Год назад

@@jonny621 I would say you are searching in the wrong area to solve the problem then. Something else is wrong.

@justobservenow3480 4 месяца назад

My 2023 yz 250x was having rich jetting problems fouling plugs. It only has 3 hours on it. And the last couple of times I rode it it was sputtered and died. The smell from the exhaust was like plastic instead of the nice yamalube smell. Im running 32.1 non ethanol 87 pump gas. But the gas is from ealy September 2023 . So someone said old gas smells plastic like when burnt

@HorsepowerHouse 4 месяца назад

Dude get that ancient fuel out of there. Fuel starts to go bad after THIRTY DAYS! And only use non-ethanol fuel with Sta-Bil and your good quality premix oil. I bet your carburetor could use cleaning as well. And check the spark plug. If you have videos of it running, send the links.

@adamwilson5635 Год назад

Thank you for putting up this video on jetting.i have a 91 cr250 I just finished putting back together, and have never messed with tuning a carb before. Your examples will help, I hope. Also, what do you have wrapped on your fuel line? Thanks

@HorsepowerHouse Год назад

Heat shield

@adamwilson5635 Год назад

@@HorsepowerHouse is it to protect the fuel line, or keep fuel cooler?

@HorsepowerHouse Год назад

Keep fuel cooler. Colder fuel makes more power than hot fuel. Always refrigerate your fuel or at least keep it cool in the shade or in a cooler with ice.

@redcreator3532 7 месяцев назад

I curently ride in winter (i ride 125 2t beta enduro bike) but I have a problem with the air/fuel needle because I can only turn it for 1 turn and than starts to go realy hard (so that means Im always on rich side and the bike realy wants to die it isnt running good) but normaly I could turn it like 4 turns. Is this normal for Keihin carburator or is it becaus I run summer jetting?

@HorsepowerHouse 7 месяцев назад

What is the climate where you ride? Temp, altitude, humidity. If it is quite different in winter vs summer you have to richen up your jetting for winter colder weather. Pilot jet and Main jet.

@redcreator3532 7 месяцев назад

Hi, its around 0 degrees celsius. I wasnt changing any jet only air/fuel needle. I richen it up like month ago it was running good but now it wont even stay running.@@HorsepowerHouse

@HorsepowerHouse 7 месяцев назад

Richen pilot jet and main jet. Should solve it.

@redcreator3532 7 месяцев назад

I will try, thanks for advice!

@Isaiahstetson Год назад

So my 2020 Tc125 Lecteon carb dirtbike was running lean at one point to where it was bogging, I made it 1/8 turn richer and it made it to rich. And I go 1/8 turn leaner and it’s to lean. What do you think I should do?

@HorsepowerHouse Год назад

There is something else wrong.

@mineer-pg5sv 8 месяцев назад

To rich is much better then to lean i almost blew my bike up a few days ago because of an air leak which made the bike lean keep that thing richer then leaner

@skipperjones7490 3 месяца назад

My 2024 YZ 250 runs good but my spark plug is a dry black. My buddy said it's running a little too rich. I changed the pilot and main leaner from stock but it didn't run good so I went back to stock. If I back this air screw out a little will it lean it out so i don't foul a plug deep in the woods?

@HorsepowerHouse 3 месяца назад

The video is your friend. Follow it's lead...

@SuperRedsCichlidChannel Год назад

What size jets do you usually run in cold Temps?

@HorsepowerHouse Год назад

Larger than summer temp jetting. Depends on where you are in the US though. Hot humid usually needs leaner jetting. But hot dry conditions need richer (to keep the engine cooler.) Colder drier air usually needs richer jetting (because the bike is breathing cleaner air.) But there is a fine line all depending on the conditions you are riding in.

@mclovin_it8872 11 месяцев назад

Just got my yz85 couple days ago and i drained out the old fuel and poor in new! It smokes alot when idling. Would that have to do with the carb adjustment or is that some internal issue? The previous owner installed new carb i could tell and he said he hadn’t adjusted the carb when he installed it.

@HorsepowerHouse 11 месяцев назад

Let me guess, you got it at a really really good price...

@mclovin_it8872 11 месяцев назад

@@HorsepowerHouse haha yup 2006 yz85 for $1,600 i can tell it idles high! I started it up lastnight but it was getting late and didnt want the neighbors to call the cops for a noise complaint so i was going to see whats up with my carb and adjust it if possible.

@HorsepowerHouse 11 месяцев назад

@@mclovin_it8872 it could be any number of things, my man. I recommend you get some professional help, maybe from a mobile mechanic who can come to you, otherwise you will be chasing your tail for who-knows-how-long.

@mclovin_it8872 11 месяцев назад

@@HorsepowerHouse alright ill do that and see what they think or recommend Thanks!

@HorsepowerHouse 11 месяцев назад

Let us know what you find out. It can be any number of reasons why a motorcycle will not idle properly.

@peekingtom8337 3 года назад

What's on your fuel line

@HorsepowerHouse 3 года назад

Heat shield

@peekingtom8337 3 года назад

@@HorsepowerHouse also, I'm currently living in blairsville ga, about an hr north of talking rock. My 2020 250x is only getting one ride per plug and I know the jetting must be off, I'm having to run the br7es plug to make up for this. Any suggestions on a main jet or pilot jet per season that have worked for you? Ridden yzs all of my adulthood love the bikes

@peekingtom8337 3 года назад

@@HorsepowerHouse most frustrating my local yamaha dealer suggested I use the bpr7es.. would that not be at a risk of detonation? I'd like to resolve my issue completely and run the recommended plug I'm trying to get my bike in order before oct because I will ship to parris island then for 3 months of training, want to come back to a bike ready to go

@peekingtom8337 3 года назад

@@HorsepowerHouse one more thing... does that headshild affect how the bike runs as in improvement or simply to preserve because of the expensive cost of fuel line these days

@HorsepowerHouse 3 года назад

@@peekingtom8337 colder fuel makes better power than hot fuel. Simple as that. And if you refrigerate your fuel and /or use heat shields on the bottom of your gas tank you will gain horsepower.

@auskilluminati333 2 года назад

I've been changing my jets and checked the rubber O ring on the air fuel screw is seated. But I still am having issues with air fuel adjustment. It does not change idle no matter how far In or out I go. And I've gone down. In jets and up 2 sizes with no change. Moved.the needle seat down 1 but noticed a bit of pinging. I'm at a loss