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Search the forum for keihin carburated 2t models up to 2016. I dont remember the jetting, but use the NECJ needle from a Suzuki.
Edit: Main: 160. Pilot: 40. Needle: NECJ.
Part #13383-37FE0 for NECJ needle.
Jetted my 125 -19 properly and people think its a 150, i shaved the head and put 1mm of squish too.
40:1 motul 800 with ron98/mon94 oxygenated fuel.
HGS Pipe and silencer.
PW 2 1/4turns in from fully turned out.
520 main
25pilot jet
Stock 4.0 slide
S-7 needle jet
42-75 needle put at 2.5 clip
(i use schims to go half clips)
BUT it ran a little lean at 3/4 throttle(tuned by ear)
So i put the needle in my drilling machine and modified it were it was lean( filed down probably 0.001mm).
(see picture, see the needle in the middle were there is some file scratches).
Been riding it hard(A class) for 95 hours, 3 top ends. No problems other than adjusting the air screw every practice.
Been riding all year from 15 to 90 fahrenheit no problem ! Pulls like a train and just keeps going.
Recently got a 250sx -22. Im gonna put AJ's jetting to the test. 5.5 isch cut slide and all the other specs.
Running 40:1 motul 800 with ron98/mon94 oxygenated fuel. I put the needle clip in the 3 position since its 15 fahrenheit outside.
// Mattias
The Shop
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I think the needles are anodized aluminum. I'd be a little concerned about your mod removing the anodizing and making the needle subject to wear or corrosion. I'm sure you're keeping a close eye on it.
Been running the needle like that for 90hours and no problem. Just sold the 125 so now im on a 250sx.
I did as hylo recomended and ran the needle at the third clip pos. Ran great up til between 1/2-3/4 throttle, went very lean and the rpm's took off like a rocket. This with a 500main. I had to bump the pilot back to 35 because 32.5 was too lean.
Will do some more testing with a 540 main.
It sounded better and the rpm didnt take off when I ran it on the stand. (Zero load I know but thats how I jetted my 125 and it runs perfect)
Running 40:1 mix.
//Mattias
Been ghosting this post along time and I appreciate all the work you guys have been putting into this, so I finally bought the number 5.0 slide for my 2018 KTM 150 sx. As I don't want to cut my 4.0 slide and keep that one stock.
I have the JD block jet gasket all ready.
So should I just run the slide as it is or should I file the engine side notch to 3mm with a 4mm file?
Is there anything else I should do? Been seeing people drilling holes to the float bowl nutt etc..
Best regards Adam
Pit Row
So I recived the JD gasket kit and the number 5 slide, so i'm about to get everything sorted tomorrow or this weekend
If I decide to do the notch should I go one step leaner on the pilot jet to a 30 from 32.5 as you described on the first page? I don't know what temperatures or elevation you where testing at.
I'm at sea level and it's around 23F to 41F at the moment.
This is my plan
MJ 540 for sand tracks
PJ 32.5 or go to a 30 if I do the notch?
Needle Jet S4
AS 1.5
slide 5.0
Needle 42-74 on the 2nd clip
Needle jet S4
PV 1.75
Fuel mix 40:1
I'm asking because I have very limited time with both work and 3 children at home, so I want to get everything as close as possible and just enjoy my bike.
Thanks
Really don’t understand mikuni needles and what they mean, like 43-72 what’s the 43 and 72 mean? Tamper and length?
https://www.thumpertalk.com/forums/topic/1223312-discontinued-mikuni-ne…
A 43-75 is half a clip richer than 42-75. How much leaner is 42-74? It is smaller in diameter, so it should be richer at first at least, but still half a clip leaner according to the chart.
This confuses me.
In practice, I'd say most people will notice 1 whole clip change more than they will notice a 1-step change in diameter.
I have about 10-12 of the 6BFY series needles and enjoy experimenting and fine tuning for conditions. It's really nice when you get it right there at the sweet spot and can make it really perfect with 1/2 clip changes, etc.
It is actually pretty funny, when I posted the question I was jetting my bike here at home. A bit of experimenting and a whole lot of curiosity. And I wanted to do it properly, without the feeling of having to hurry to get my fill of track time. The temps here in Norway fluctuate a lot from summer to winter and my bike was jetted in 15C celcius. It is now -5C celcius.
Anyways, I tried the difference between 42-74, 42-75 and 43-75. It was bang on with what you wrote. The difference between 43-75 and 42-74 was minimal, but the bike felt rich with 43-75 around 3/8 throttle pos with third clip. 42-74 felt good but not great. I ended up using 42-75 since 43-75 didnt feel as good. I am now content and happy.
Not sure the neighbours are though. A 250 up and down our street maaaany times.
Post a reply to: 125/150/250/300 KTM/HUS/GG jetting thread