Perfect YZ250 Carb Tuning PWK How To (Get Your Jetting Dialled)

This is a comprehensive look at the Keihin PWK. This example is from a YZ250, but the design is very similar to all modern Keihin PWK carburetors.
This is the foundation for perfect jetting. Without a clean and properly set up carb it's impossible to get it right.

[@amello98]

I picked up a 2002 YZ250 in pieces. All your YZ vids have been super helpful- from the engine rebuild, lacing up black wheels and now the carb. Thanks! Keep them coming!

[@chadrides914]

Best Kehin carb vid on the entire interwebs. Thanks TrueTech.

[@Kevin-wy8kc]

but that not what he said it was. super annoying

[@aklaunch]

Bravo!! One of, if not the best video on this subject that exists

[@markbrynteson5141]

Thank you sir, very informative

[@4x4American]

Great video, thanks!

[@nastysoda9212]

Thank you! Really appreciate you talking thrrough what you're doing, other videos jsut have some timnelapse with music which helps me Zero.

[@griffenyoung5958]

What a great video!!

[@Randy_Cox]

Great video. I bought a 2024 yz125x and had to change my main jet at the track. When I did it I had to unplug both the throttle position sensor and power jet connections so I could rotate the carb. Once I got the jet changed I completely forgot to plug the electrical connectors back in.....but the bike ran great, no over rich loading up like it had before and I rode all day. The next day during preride check I seen the connectors and rehooked them back up. And didn't notice any difference the whole day.😂 Looks like I need to get a 40 power jet too. Edit. After a little more looking into this and reading the yz125x manual doesn't even say it has a power jet, or where it effects the fueling. So even though it is the same carb with the same parts, per the manual it doesn't exist on the 125. LoL

[@ericmahoney5916]

How is everything with your 125x? I just got mine 3 weeks ago and threw in the jd jetting kit, but nobody seems to know much about this carb and bike combo

[@Randy_Cox]

@ericmahoney5916 I have a couple videos on my channel about jetting it and now she runs like a champ.👍

[@camselkirk7248]

Excellent video, highly underrated KZbin channel. Keep it up man. I’m working on my ‘98 CR250 at the moment and trying to figure out why it won’t idle. It appears to be running rich so I think I need to change the pilot jet. That being said, how many different sized power jets should I order? Just one size at a time?

[@ChuckfromTrueTech]

I haven’t messed with the power jet on a CR, I’m not sure, but first it’s important to verify that everything else is in good shape: carb clean, reeds, piston/cylinder, crank seal, spark plug, air filter etc. Once all that checks out it’s time to change jets.

[@jeffmurphy402]

Quality video. You know your shit!

[@dakstaverman62]

Hello i have a 06 yz250 im in ohio at 850 above sea level,i have fmf fatty and shorty silencer and vforce3 reeds i ride woods and am more steady on throttle,should i run 175,45,3 clip down and 40 power jet? And i run 32:1

[@wjb111]

Great informative video! What brand/source breather line do you use? Earned a Sub. 👍🏻

[@ChuckfromTrueTech]

I buy it through a wholesale supplier I deal with. Not sure of the brand. I buy it in a large roll.

[@01camarosspower]

What is your go to premix and ratio? Awesome video and very helpful!

[@ChuckfromTrueTech]

I run 50:1, but I ride mostly technical rocks. Primarily low RPM. For higher RPM riding I would be mixing richer.

[@surfpr727]

Thank you for such an excellent video. Do you run your YZ250 on trails or hard enduro? Do you think that the YZ250X is better for slow trails and hard enduro?

[@ChuckfromTrueTech]

This YZ is a big learning project for me. I rode a YZ in trails for years and now my primary bike is a TPI. I’ve ridden this YZ in some proper hard enduro terrain, but it just can’t compare to a proper enduro bike. It’s good, but not excellent. The X is better for hard enduro, but it’s still no enduro bike.

[@surfpr727]

@@ChuckfromTrueTech thank you, I really appreciate your perspective.

[@seanbalaun8963]

Hey Chuck. Thanks for the video, but...believe it or not...Yamaha has a mistake on their chart in the YZ250 manual. The power jet actually works from about 1/2 throttle to full open. Yes, the solenoid will close the circuit at higher rpm (to allow the engine to rev cleanly to higher rpm), and while open at lower rpm will allow a richer mixture for better throttle response. If you track the carbuetor's power jet circuit you'll see it enters the venturi at the point the slide would be about half open, so it "physically" limits the flow through the circuit from that point to full open.

[@ChuckfromTrueTech]

Different years of YZ250 manuals have different graphs for the jetting. Maybe that’s why. 🤷‍♂️ What I know for sure is that the difference is immediately noticeable when the power jet is changed.

[@CraigSteinman-zt3vu]

I take it TANGO stands for T and FOX TROT stands for FT in the power jet part#?..thank you for the video I definitely need to change my power jet

[@natewrenn7723]

Quick question for the 2 stroke keihin portion.. between the needle clip and cable holder is that a spring and rubber gasket? My carb seems to be missing any parts on the inside of the cable holder??

[@ChuckfromTrueTech]

Some PWK carbs have the spring & some don’t. I’m not sure what the reason is, but most KTM & Beta carbs don’t have it.

[@eddiewallin3157]

I was wondering my manuel says power jet kick in a 1/2. Throttle

[@ChuckfromTrueTech]

Different years activate at different times.

[@danielplace1962]

The tps doesn't control the power jet solenoid in any way. The ecu triggers it and it is rpm based. Solenoid closes off the power jet at 8500 rpm.

[@northernspur6282]

What is the name of the catchy little tune, I don’t normally like music over a tutorial but this one’s cool .

[@ChuckfromTrueTech]

🤷‍♂️ It was from some copyright-free website. Thought it fit the bill.

[@willcountypowersports6338]

Awesome video, where can I find that carb cleaner at? Can’t seem to find it thanks

[@ChuckfromTrueTech]

Suzuki has discontinued it but Yamaha & Honda still offer it.

[@willcountypowersports6338]

Is the Yamaha combustion chamber cleaner the same thing that’s the only thing I can find.

[@zackiaryruddick701]

Hey chuck , so when you set the float Hight you say you want the float arm to just touch the needle without comprising it , mine compresses it like halfway in so I have to bend it quite a bit to do as you said, I'm just not confident yet brand new bike and it came like that but not running very well, how would it affect the bike if the pin is being compressed halfway in instead of just touching it ??

[@ChuckfromTrueTech]

The float will close the valve as soon as it presses the needle against the seat. Measuring halfway compressed isn’t accurate. Your float will close the valve too early resulting in a low fuel level. The bike may run lean.

[@zackiaryruddick701]

@@ChuckfromTrueTech thanks for answering so quickly, I will reassess the float Hight I'm sure it's way out , but the only thing is the bike was using alot of fuel and seemed to be running rich , so I jetted down the main and pilot and the power Jet to a 40 for the yz250 like you did in your video but I didn't change the needle position and the bike felt much better but I think I need to change the needle to a richer position as the bike is lacking top end pull , I'm just wondering if the float Hight is way out that means my jetting will need redoing yea ?

[@brettlaage9687]

@@zackiaryruddick701I saw in another video that you hold the carb at a 60 degree angle to measure float height. It was for a Beta, but with the same carb. I think that they want it at an angle so the weight of the float doesnt compress the needle.

[@ShortBusEnduro]

Do you change power jet without downsizing pilot and main? I’ve downsized my pilot and main 2 sizes for my style and elevation but I wasn’t sure if changing power jet is gonna lean it out too much. I’m barely on the pipe most rides, not smoking, no spooge and plug is still black, not chocolate brown.. 2021 yz250 with 3hrs on it. Single track and trails

[@ChuckfromTrueTech]

Yes. You can change it independent of the rest of the jets. If you’ve gone sown 2 sizes on pilot & main it’s very likely that your needle is too rich as well. You must be up at elevation to be making those changes?

[@ShortBusEnduro]

@@ChuckfromTrueTech I installed the next needle size down (n3cw-2) along with jets. I’m at 400ft and ride from sea-level to 2500ft, probably 1200ft more often then 2500ft. I’m old, I ride slow and much prefer the mx style bike over “trail” bike, just cause of the way I ride and I like a stiffer suspension. Before I changed jets, I would come out of a corner on a trail… hit the throttle and it would foul the plug everytime. Tried needle first, but still spoogey and fouling… that why I went with the “drastic” changes. I just got my #40 power jet in the mail yesterday. Should I swap power jet and put stock needle and jets back in?

[@ShortBusEnduro]

#172 main #45 pilot

[@elcincero321]

​@@ShortBusEndurowould be better to go back up to 175, check new plug and look for brown chocolate tip and if not 172 is your way to go.

[@Fox250R]

Does the power jet only apply to yz250s or can other PWK carbs on other bikes benefit from changing the power jet?

[@ChuckfromTrueTech]

I haven’t experimented but I have heard of guys changing it on other bikes as well. Most recently the KX250.

[@mozer30]

Is the power jet size marked on the jet like the main/pilot. I haven’t got a screwdriver small enough to check the size 🤦‍♂️

[@ChuckfromTrueTech]

Yep. There’s a little Keihin symbol and the size.

[@mozer30]

@@ChuckfromTrueTech thank you for the reply 👍

[@johnnyblair6034]

What altitude and temperature would you say the jetting on this carb is ideal for?

[@ChuckfromTrueTech]

That depends on your engine, air filter, pipe, fuel & riding style. I completely changed it after test riding the bike. The 40 power jet is the only part I kept.

[@EkonRekon]

What years of YZ250 does this apply to? I've got a 96'

[@ChuckfromTrueTech]

‘96 didn’t have it. Looks like it started in ‘99/‘00. The rest of the carb is similar to tune.

[@justinrupert7233]

What do you use in your ultrasonic cleaner?

[@ChuckfromTrueTech]

I use water & about a litre (quart) of Zoom Motorcycle Cleaner. It does a good job with aluminum parts & getting dirt stains off, but not great with anything greasy. It works well for me because I generally degrease in my varsol tank first.

[@alwynjones465]

Will the 40 power Jet be ok on 23 y125?

[@ChuckfromTrueTech]

I haven’t tried it on a 125. Easy to test though.

[@MS-ye9vx]

If you use the Suzuki 3 taper needle necj like you mention do you change any of the other jetting?

[@MS-ye9vx]

And what clip position on the necj do you start at? I’m a New York woods rider. I’ve been reading a lot in forums also. Awesome video thanks!

[@ChuckfromTrueTech]

Yes. Since the needle is thinner at the end you need to use a smaller main. I think I ended up at a 160 on the YZ.

[@ChuckfromTrueTech]

@@MS-ye9vx I started in the 3rd clip position, but I'm down to the 2nd and I'm going to go another half a position. I never trust any jetting charts. Every bike is a little different.

[@MS-ye9vx]

Thanks for the quick reply. I’ll give it a shot!

[@kentooney5988]

any opinion on JD needles?

[@ChuckfromTrueTech]

I never experiment with them because it’s tough to find good info on them and the JD kits are over-priced if you just want the parts. I don’t need a kit. I have all the individual parts, so I just make the exact change I need.

[@Jordan348_MX]

I've got a 2023 YZ250, just put the FMF exhaust on it. Jetted it to 175/48 (FMF specs) Still drips at the pipe/silencer connection and out the tail pipe. I am running 927 premix 30:1, I am wondering if I need to go to 40:1. or maybe the bike is just not broken in yet, its got 5 hours on it.

[@ChuckfromTrueTech]

Unless you’re an aggressive motocross racer 30:1 is too rich, but spooge is almost always caused by a fuel rich (as opposed to oil rich) mixture. Every bike & every rider is different. The FMF chart can be a good starting point but you will need to tune the bike by riding it in your actual riding environment. It certainly sounds like you’re too fuel rich as well.

[@Jordan348_MX]

Thanks for the reply. I’m trying to learn how to get this thing tuned. Do you think going to 40:1 would cause less of the spooge build up, or should I try adjusting jets again? I’m def a weekend warrior riding small motocross tracks in Florida at sea level.

[@ChuckfromTrueTech]

I don’t expect reducing the oil will affect the spooge. Reducing fuel usually does. Have a look at that YZ jetting chart in the manual & go through the instructions. They’re better than the FMF recommendations.

[@Jordan348_MX]

Thanks, I found the chart in the catalog, it appears my new jetting is leaner than stock, but I think my oil may be the problem. I'm using Maxima 927 which has a very high flash point 420 (almost double of Yamalube-255) and from what I read you really have to hammer that throttle and ring the bike out, which I'm def not riding hard enough. For starters I am going to go to a regular premix like the Yamalube or HP2.

[@Jordan348_MX]

Thanks for the info! I also just picked up a 2024 YZ125 and I've noticed that when I turn the gas off and let the fuel run out of the carb, just before it turns off, it revs really high and the RPM's shoot way up before shutting off, my YZ250 does this a hair, but not as high on the RPM's. It's brand new and starts on the first kick, doesn't drip and pulls like a monster for a little 125. It came with the V-Force 4 system from Yamaha. I assume it's due to getting air but slowly starving of fuel since it happens right before it runs completely out. Any reason to be overly worried about this?@@ChuckfromTrueTech

[@MrJeffharper47]

Two questions: Why go to a 40 power jet? And what’s so special about using a Suzuki needle in these carbs?

[@MrJeffharper47]

Wait, just got the the end of your video, I see you changed the power Jett because it was too rich. But why the Suzuki needle?

[@ChuckfromTrueTech]

The Suzuki needle is a triple taper instead of dual. It tends to give a smoother feel in the bottom to mid-range. It’s not for everyone, but I like it.

[@MrJeffharper47]

@@ChuckfromTrueTech I see. I’ve heard people talk about it on the YZ250 Facebook page I’m a part of and I’ve always wondered.

[@justobservenow3480]

I've been running 32.1 on my 23 yz 250 x. Is that too heavy and will i sustain damage by running it at that? Everything is completely stock. Only 3 hours on the bike. 87 non ethanol fuel and yamalube.

[@ChuckfromTrueTech]

You won’t hurt anything with 32:1.

[@MrJeffharper47]

You definitely need to run at least a 90 octane fuel. That’s what the manual on my 2006 calls for. 93 would be better. No need for “Race” fuels if the bike is mostly stock

[@250ridr2]

Nice idea but what is your elevation?

[@ChuckfromTrueTech]

Personally I ride from sea level to 8000 feet regularly, but if you’re higher you might want a smaller power jet.

[@250ridr2]

Yeah I'm at only 850 ft rarely go much higher

[@SoCalMisfit712]

Hoping u can help me. 2023 yz125 jetting is trash stock. Pilot is close at 62 I could go down to a 60 or 58. Main is 165 which is also close I could go up a little and play with it. I have a horrible bottom end bog, you snap the throttle without the clutch and it wants to die. I’ve went to the richer needle on the bottom clip and it is almost there. Everything I’ve seen and read everyone is going leaner, but I’m thinking richer on the needle since it’s getting better the farther I go down on the clip. So should I jump up to the next thinner needle, meaning smaller diameter in the straight portion with the same taper starting position. Or should I chase it up with the taper position. There is only 1 richer with the position difference so nydf to nycf which is only a 1/2 groove richer. The needle I’m thinking of going to is nyde which would be same taper start position but 1 step richer on the straight portion. Which by the graph I have in my manual controls closed to 1/4 throttle. I know pro circuit has a y3 needle which they say cleans up the mid but they still don’t have it in stock, and I can’t find it anywhere. There is a y4 needle but they also said they’re still testing with that one. I got the jd jetting kit but it’s way off 50 pilot and I have a half to 3/4 turn on the pilot and it just sounds lean down low. Their main is at 175 and to me seems way too big, and the needles make the bog worse than before. Only other thing I can think is the mid body gasket but the carb is new, but doesn’t mean it’s not bad. Or the power jet but in my manual it says under 8500 to the extent of 1/2 to full. Any help would be appreciated thanks.

[@ChuckfromTrueTech]

That’s a lot of info. It sounds to me like you’re stuck in a vortex to too much information. It sounds to me like your pilot isn’t sorted out yet. I expect that with everything stock, if you go up a little on the pilot you may get closer to a diagnosis. Most bogs like the one you’re describing are caused by the pilot.

[@SoCalMisfit712]

@@ChuckfromTrueTech it doesn’t bog off idle when I snap the throttle in neutral. It’s under load when in gear. I had a 50 pilot in it and it was lean bogging snapping the throttle in neutral. Air screw was 1/2 turn out. The bigger pilot fixed that, if I go any bigger you loose the air screw tuning. Meaning a pilot over 62 and I’m 3 turns out and it’s a burbling mess. 🤷🏼‍♂️

[@Randy_Cox]

My 2024 yz125x likes a 52 pilot, 172 main. Stock needle on top clip position. The bikes come to rich down low, to lean up top. This power jet talked about in the video is probably another cause of so rich down low, so if you change the power jet like described you might have to go richer on pilot since your leaning out the power jet.

[@SoCalMisfit712]

@@Randy_Cox what is the stock needle?

[@Randy_Cox]

@SoCalMisfit712 NYCF is stock needle for 2024 yz125x

[@dakstaverman62]

Forgot to mention air mixture screw was 1.5 turns out and the reason is that im fouling plugs,thank you

[@ChuckfromTrueTech]

There are too many variables to be able to say what jetting you need. Each bikes is a little different. If the engine is in good shape you should be very close to stock. If you’re struggling it’s often helpful to go back to stock and make small changes from there. Jetting charts are often way off.

[@dakstaverman62]

Would you still recommend the 40 power jet?

[@ChuckfromTrueTech]

You need to test every application, but I've found it to be helpful on most YZs I've jetted.@@dakstaverman62

[@dakstaverman62]

Ok great thank you

[@007BlackGuy]

I can smell the video

[@ChuckfromTrueTech]

🤣

[@jfratis9081]

YZ250s are track bikes. If you keep the jetting from factory and then are lugging them they will foul plugs. If you want to putt around on trails, before you swap to an 18'' rear wheel or anything else determine what oil you are going to use, what ratio, and then rejet.

[@ngrimm0]

My yz250x does the same thing. Changed power jet all good now

[@gumpycognac4505]

was never taught to say “zed” while learning the alphabet.

[@ChuckfromTrueTech]

Most likely because Zee rhymes with G, P, V, (the last letters in each line) in the alphabet song. Zed comes from its Greek predecessor “Zeta.”

[@jamesoso259]

Soo lean I wouldn’t even touch a sand pit

[@knighthawk3559]

Chinese carbs are best for power.

[@ChuckfromTrueTech]

🤣

[@Kevin-wy8kc]

the generic piece of paper he shows you starts at about 10:27 and is about a minute long and not game changing. Who wants to watch another carb cleaning video?