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Only $10 for all 2026 SX, MX, and SMX series.
Main - 540
Pilot - 35
Needle - 42-74, clip 2 (possibly 43-74 on clip 2 when you get down in the colder temps)
Needle Jet - S4
Slide - #5 slide from JD jetting
AS - 1.5 to 1.75
Make sure you replace the jet block gasket with the one from JD. Make sure you set the float height correctly to 7.5 - 8.5mm
Jets are ordered, wish me luck. Thanks guys. just had shoulder surgery so I wont be able to test for a while.
Have a 2020 ktm 125. Ran great first couple months from new. Then i started chasing my tail with jets. And nobody could point me in the right direction. Somedays i could get it close but always had that 1/4 throttle bog and rich pilot that i couldnt shake. I couldnt get a slide as they are on back order here. So i cut mine which was easy enough.
i have put all specs in listed and keen to see the results when i go for a lap on the weekend. Bike has a pc pipe and r304 shorty, tsp head and vforce4.
cheers for all the info. I would of never stumbled across a setting like this otherwise.
Assuming you are using this spec from page 1? :
MJ 510
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 2.25 turns in from all the way out.
Fuel mix 40:1
These specs were without the extra notch on the front of the slide that you have there. With that notch, you may need to do a 30 pilot. Especially if it is hot summer down in Aus right now. Just be aware of that. What fuel, oil, and ratio are you running?
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Yer following specs from page 1. And i have put. 30 in the pilot for the notch and it is also between 30-40 degrees most of the time when im riding atm. Running unleaded 98 with motorex 2t oil @40:1
Let us know how it runs.
2022 250sx
FMF pipe and silencer
MJ 490
PJ 32.5
AS 1.75
slide 5.75 from JD Jetting
Needle 43-75 on the 2nd clip
Needle jet S4 (KTM part #55431021400)
PV 2.25 turns in from all the way out.
Fuel mix 36:1 Motorex
2:1 91 pump gas/100LL av gas
Bike is slightly lean its seems on the top and a high idle. but the air has been cold in AZ. 500 Main now installed and will try a 35 PJ in it this weekend. I think the recommended settings would be prefect during the summer
Overall the bike is way more crisp from the mess it was stock lol
Back the power valve out 1 turn and mix the fuel to 50:1 with the 500 main. When the temps are below 40 I have to go to a 35 pilot and the 3rd clip on the needle especially with ave gas or 50/50 T2/ethanol free pump. I can’t comment on the idle as I have mine set to stall if I let it try to idle by itself.
I'm riding AZ also and all my settings are the same as yours except I am at 1.25 - 1.50 on the PV as AJ said. My bike is a 300 now and I am on a 35 pilot. I was on a 37.5 when the temps dropped when it was a 250. I run straight Avgas at 38:1.
Took bike out couple of weeks ago and was getting a bog in corners and when snapping the throttle on. apon reading abit more through here seen someone with similar issue where pilot was to lean. I have since changed to 37.5 pilot and 520 main. I took bike out again on the weekend and all i can say is wow. What a differance, bike has never been so crisp and responsive through the entire throttle range, no longer loads up when idling.
Thanks Heaps
That's great. Glad to hear it's rippin'....
GasGas MC250 2022
HGS silencer and pipe
VHM 12 set piston and insert of 22.60 cc
Main jet 500
Pilot jet 32.5
Slide 5.75 (Filed by hand)
Needle 43-75 (KTM part #55431134400)
Clip position #3 (mid)
Needle jet S4 (KTM part #55431021400)
Air screw 1.5-2.0
Fuel 32:1
Pulls strong on top, but at part throttle and mainly when closing the slide I will hear a hiss/quack/wha. I was thinking a lean condition part throttle so raised the needle from 2 from top to third. Seemed to help, will try raising it a notch more next time I am out.
Caveat, fuel is Octane 100 that has been sitting for 4 months.
What is the Temperature and elevation? On my MC250 I was mostly same jetting as you... but running 38:1 and and 43-75 on C2. I was using a 37.5 pilot with this when it was cold out. I'd try going to 35 or 37.5 if I was you.
Has anyone used the TSP offset woodruff key at all? I ordered one, going to see how it performs. Hopefully a little more midrange on the 150 for some enduro stuff. Edit: Sorry i guess that's not jetting technically
Thanks for getting back to me. I’m at sealevel, on that day it was 8 deg C. I’ll get an 37,5 as well
Whats up guys. Needing a little help here with my 2022 KTM 250sx. In 2nd and into 3rd gear only, my bike has a weird bog and seems to only happen right after the mid-range when the powerband starts to kick in. I am running the setup below. I have the stock expansion chamber with the r304 shorty. I run straight AVGAS 100LL with Amsoil Dominator at 50:1 with PV about 1.5 in from all the way out with the standard PV spring. When I'm in neutral and warming up the bike it sounds so crisp and doesn't miss a beat, only occurs when I'm twisting the throttle wide riding on the track. Thank you! *stock reeds as well*
Main jet 500
Pilot jet 32.5
Slide 5.75 (Kawasaki part#16025-0003)
Needle 43-75 (KTM part #55431134400)
Clip position #2
Needle jet S4 (KTM part #55431021400)
Air screw 1.5-2.0
Fuel 50:1
My bike is a 300 now, but when it was a 250 I had almost exact same specs as you also using straight 100LL. Except I was running a 37.5 pilot and the bike ran excellent. (40-60 degrees. Summer I ran a 35). I was also on 38:1 with Motul 800. Try the 42-75 needle on clip-2 at some point also. I went back and forth.
Would I need to mix it richer then with the 100LL? I will try the 35 pilot, I am here in FL so temps are around 70-80 at current. Riding Redbull day in the dirt this weekend so I will test it then! Appreciate it man!
Pit Row
I run the same, straight 100LL. I think with us running that fuel we need a little richer jetting than the specs on page 1.
With your temps I think 35 pilot will get you better. Then try that 42-75 on C2 when you have a chance just to know how it runs. Might be a bit better.
Okay I will give it a try. Why did you run motul 800 at 38:1? Out of curiosity, what pipe setup are you using and which color PV spring did you use?
I run the 800 because it's very good oil and runs excellent. I have no experience with Amsoil but I hear it's very good. I believe that's what AJ did all the original settings with. I run 38:1 because Motul is a European oil and comes in liter bottles instead of quart bottles! It's just easier to do 500ml per 5 gal of fuel instead of 16 oz. That makes it a little more oil than 40:1 and takes it to 38:1. No other real reason for that than I also like more oil than 60:1 or 50:1. I also have a 125 that I run at 38:1 so it makes it easier to have 1 jug.
I am running an FMF Factory Fatty with Powercore-2 silencer (normal length, not shorty) and the stock PV spring at 1.25 - 1.5 turns in from all the way out.
Okay good deal man. is it a myth that more oil will create less power? I will try your ratio and oil for my next jug and see how she likes it. I definitely want the FMF system, will be getting soon. Would it be a possibility i was getting a lean bog with that 32.5 pilot? I never got the bog until I tried sunoco 110.
Basic old school 2-stroke wisdom is that more oil always creates more power. This is due to better ring seal and better lube on the bottom end. This assumes you are jetted for that ratio, of course.
Yes, totally possible you were getting a lean bog with too small of a pilot. When my bike was a 250 it ran very well on the 37.5.. even at slightly higher elevations like 1500ft.
Dang alright I will definitely give it a go then! So, the specs I am currently running, with a 35 pilot, should be sufficient for the Motul 800 @ 38:1 correct? Was there anything else you did to the 250?
Just to throw some info out there, the PC pipe and silencer made more power than the FMF did. In either case you want the long silencer.
currently 141 hours on the stock bottom and running 55:1 with 51 on this current top end.
Hey alright, are you running the standard 304 then? And what is your thought on the slight bog i am experiencing? Switched to a 35 pilot and im testing this weekend. running the 100LL @ 50:1 amsoil dominator.
I had a long reply typed out and the server had an error when I hit submit.
yes, the 304.
yes it could be a lean bog. Could also be a bog that the 1/2 clip position of the other needle FGR mentioned would fix. Thats what I had happen with me. I had the bog with straight race fuel which the 100LL runs similar. I also had a rich bog in between jumps that I had to drop the pilot one size to fix. I think I have the 35 in there now and the 37.5 caused the bog. I run the 37.5 when it’s below 40, anything over that I get the bog. And this is how my bike it, not saying that’s how yours would be as each runs a bit different and weather/location plays into it.
I switched out the mikuni for Keihin 38mm on all of my ktm 250/300s. Running 40:1 maxima K2. They run absolutely amazing. Smoother and more power everywhere plus much needed over-rev.
Have you have it on a dyno ? i would think that you are right that is maby smoother and more power down low but i think that the mikuni will have it coverd when its comes to overrev.
Did both the Keihin and the Mikuni on my 250/300 (and a few 125's). Keihin has a wider window of "acceptable" performance, i.e. is easier to nail a workable setting. Mikuni has better performance once dialed correctly with the jetting from this thread, especially overrev. With the Mikuni you may only be 1-2 steps off on jetting and pull your hair out before you ever get there though. So the Keihin is maybe a better first option for guys that don't especially like tinkering with stuff or care to learn a whole lot about jetting.
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