Upgrade to enjoy this feature!
Vital MX fantasy is free to play, but Premium users receive great benefits. Premium benefits include:
- View and download rider stats
- Pick trends
- Create a private league
- And more!
Only $10 for all 2026 SX, MX, and SMX series.
Tell us what fuel, oil, and ratio you are using and also what jetting is in the carb now.
Fuel 91 Motorex oil 40:1 tomorrow I will open the carb and I will let you know wat jetting 🙏🏼🙏🏼
Hello so it is what I have so far
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Luxon 4-Post Bar Mounts
$189.95 - $239.95
Free shipping: VITALMX
I can’t read any numbers on the needle
The needle number will be stamped here.. use the zoom function on your phone to read it...
In the meantime, I will say that you'll likely be much better off by simply raising the needle clip 1 or 2 positions. You're currently in the 2nd richest position there which is likely excessive for 4500ft, especially if the temperature is also warm.
Thanks a lot I will do it and I did try to read with the phone on the needle but there is nothing stamped, I do have another needle number 6BFY44-73 the previous owner gave it to me should I use it?..and I also did some research and I see people using PJ 40 instead than 42..what you think?
Thanks again for the help
The 6BFY44-73 is a Mikuni needle. Won't work in your Keihin.
For now I would try moving the clip up 1 position. 1 change at a time or else you might get yourself lost with changes.
Yes, in other pages they recommend at least, 35 PJ if You don't notch the slide . 32.5 if You notched the slide .also you can try running 40:1 premix. Check float level heigth.
I actually found this online for Keihin carb..what do you think?
If that is the NOZI needle you have, it may be somewhat useful. Also, assuming you have the same size slide that the 150 came with when it had the Keihin that chart is for. That shows clip#2 for your elevation and mid-temps so I'd try 3 and then 2 and see what it gives you.
22 KTM 150sx owner here. I have had good luck following info on the first page, but have hit a sticking point following a cylinder porting job. Seems to have a bit of a bog off the bottom. Currently running:
MJ 480
PJ 32.5
AS 1.75
slide 5.0 from JD Jetting
Needle 42-74 on the 2nd clip (Yamaha 284-14116-H4-00)
Needle jet S4 (KTM part #55431021400)
PV 1.5 turns in from all the way out.
Fuel mix 40:1
Debating on dropping pilot down to 30 and see where that goes. Just concerned about leaning the bike out too much. Any advice would be helpful. I ride at sea level in Michigan.
What fuel are you running?
I am surprised you are so lean on the main. I'd expect you to be more in the 500-510-520 range.
Try going in to 1.5 or 1.25 on the AS. If it improves then that likely validates your belief that a smaller pilot is needed.
Running 90 octane rec fuel
To me, the bog is indicating that it is lean, and that you should be going richer on the pilot, not leaner. That 480 main does sound a touch lean, unless you’re using the bike at altitude.
Appreciate the response. I will give these changes a shot
Some really good info on here, Iv read through about all of it.
I have a 2022 ktm 125 xc that’s a headache..
currently trying the specs from the first page and on initial setup it was lean to the point of not moving under its own weight.
revved great on stand though.
Currently setup as
5.0 slide from jd
Needle 42-74 on the 4th clip!
s-4 needle jet
35 pilot
490 main
AS- 1 1/2 but really not dialed there.
it’s somewhat rideable but not great at all.
1000ft elevation, repacked silencer, good compression. 40:1 maxima k2 and motorex both. Any help appreciated!
Pit Row
You are way lean on the main. Put a 520 or 540 in it for starters.
Also, there is the 2022 issue. Does your bike have the 2022 recall completed on it (ECU replaced)?
What fuel are you using?
Is the muffler the same as the SX? No spark arrestor?
I’m running 92 pump. I have ran the stock silencer and currently the fmf 2.1 same result. Not sure on the ecu being replaced I got the bike recently and has 14hrs on it. I did already try the 540 main and it made no real difference as my problems lie on the bottom end, the bike runs great on the pipe on the top end side it’s the front low end side that’s terrible. Fair amount of spooge also but not much for smoke output.
On the one 2022+ bike with the newer ECU that I jetted, when using this jetting it got a rich bog, not a lean bog. It needed a leaner needle. The bike would start up and rev good when it was cold and as the engine reached full operating temp the rich bog would come in and it would get raw gas/oil out the pipe.
Go back to page 32 on this thread and read my post with the video of the GasGas 125. The jetting I ended up with on that bike was:
AvGas 100LL, Motorex at 40:1, vented airbox cover, FMF pipe and 2.1 silencer
Pilot 37.5
Main 540
Slide JD #5, no extra notch
Needle 42-75, clip 3
Needle Jet S4
AS 1.75 out
Depending on the humidity and temps where you are, and using pump gas, you may need a 35 pilot or even the 43-75 on clip-2.
Hi summer temperature and new problems..
I have a 2022 Ktm 150 sx PC works pipe 304 shorty silencer and Keihin carburetor setup with 40 IJ 180 MJ NOZI needle to the 2 ring and the bike still rich at the bottom with no power and spark plug super wet
i usually ride at LACR with temperature around 99F at 2710 ft elevation
any suggestions?
thanks
Historically that NOZx series is too rich in the first 1/4 throttle. Check ktmtalk jetting forum for needle guidance.
Hi guy, I will need some information.
Unfortunately the 300 sxs cylinder broke. Do you know the reference for this one? Maybe a 300 exc 2017 carburetor cylinder is identical?
I am attaching some photos of the piston cylinder.
Wanted to say thanks for all of the great information shared and pay it forward with my experience lining out our ‘22 TC125. Bike is stock except V4 reeds and FMF pipe/ silencer. It’s setup for MX with big 13 yr old (5’9” 180 lbs) that loses his mind if it’s bucking or miss-firing during partial throttle.
Initial setup below in 80-90 degree temps.
MJ 500
PJ 32.5
AS 1.75
Slide 5.0 from JD Jetting
Needle 42-74 P3
Needle jet S4
PV 2 turns
Fuel 1/3 110, 2/3 91 mixed 32:1 Super M
Ran OK but quickly realized the main was too lean and made the pipe look cool.lol Went to 520 main but fought the 74 needles and settled on 42-75 P3 to clean up partial throttle. Was still too lean on main so jumped to 540 and went 43-75 in P2 to clean up mid. At this point i believed the 540 was a touch lean but temps were climbing to 90-100+ so I left it. As it got into upper 90’s I had to change to 42-75 P2 and it ran clean at all rpm and throttle position.
Short version is 1/2 clip needle change per jet size change was required and larger diameter needle recommended. Runs flawless with setup below in 90-100 temps at 800’ altitude.
MJ 540
PJ 32.5
AS 1.75
Slide 5.0 from JD Jetting
Needle 42-75 P2
Needle jet S4
PV 2 turns
Fuel 1/3 110, 2/3 91 mixed 32:1 Super M
If you've read this far do yourself a favor and toss the Mikuni in the trash and pick up a Keihin PWK. No more voodoo magic, just smoke and smiles baby!
Don't @ me!
Good write up and glad to see some confirmation on my results with the 2022+ bikes. You've realized from your tinkering now what you'll need to do when temps and humidity start dropping. You'll end up going back to that 43-75 clip2 and likely a 35 pilot and then when it gets even colder 42-75 clip3 and maybe 37.5 pilot.
I need some help. I have a 2019 ktm 150 sx that seems to be running rich on pilot even woth a 27.5. The air screw is 3 turns out and it is at its crisp point.
I'm nervous to go any lower on the pilot. I also have what seems to be sputtering / feels like I am hitting a rev limiter right before 1/4 throttle then it clears up with a bit more throttle.
I am currently running
Slide #5 notched
Main 490
Pilot and 27.5
needle- 42-74
JD gasket
Float height- 8.80
AS 3 turns
PV 2.25
Was the bike previously running well and then developed this low end rich condition?
What fuel, oil, and ratio are you using?
What needle clip position?
Needle clip position 2.
40 :1 with 93 octane- aalways ran it this way with Yamalube premix oil
I noticed it became richer when I notched the slide. It was rich down low before but got worse with the notch.
Other than the pilot what would cause a rich condition. i thought the float was causing it but I lowered it and checked for leaking float jet but nada.
I noticed it runs it's best after 1/4 throttle but between 1/8 and 1/4 throttle its like hit a rev limiter.
Post a reply to: 125/150/250/300 KTM/HUS/GG jetting thread