KTM 150 SX 2017 carb tuning

mxallum77
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mxallum77
Hi

Recently just bought a KTM 150 sx 2017, it has the mikuni TMX carb which from reading has its issues. Just wondering what jet sizes people run to get the bike running good
any info would be great (UK rider)

thanks
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timobijnen84 10/20/2020 4:25am
10/20/2020 4:25am
6 threads down is a whole topic on ktm jetting.
There are some very knowledgeable people there.
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mxallum77
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mxallum77 10/20/2020 4:32am
10/20/2020 4:32am
timobijnen84 wrote:
6 threads down is a whole topic on ktm jetting.
There are some very knowledgeable people there.
thanks !
mxfolife732
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mxfolife732 10/25/2020 3:32am
10/25/2020 3:32am
I just did mine. Did 40 pilot 460 main 44-74 on first clip. Runs way better than stock.
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mxallum77
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mxallum77 10/25/2020 6:48am
10/25/2020 6:48am
mxfolife732 wrote:
I just did mine. Did 40 pilot 460 main 44-74 on first clip. Runs way better than stock.
Did you go up or down on the pilot jet ? As I’m not far off what your running mines currently got a 42.5 pilot 470 main 1st clip 43-73 ? Cheers

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mxfolife732
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mxfolife732 10/25/2020 6:56am
10/25/2020 6:56am
Pretty sure 470 and 45 are the stock jets. 43-74 on 3rd clip is stock. I went about 2 screws out on the air screw. Trying new plug today to make sure it’s not lean but definitely running better than stock. Running 40-1 and might buy a pro circuit shorty for a little more bottom end.
mxallum77
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mxallum77 10/25/2020 7:02am
10/25/2020 7:02am
mxfolife732 wrote:
Pretty sure 470 and 45 are the stock jets. 43-74 on 3rd clip is stock. I went about 2 screws out on the air screw. Trying...
Pretty sure 470 and 45 are the stock jets. 43-74 on 3rd clip is stock. I went about 2 screws out on the air screw. Trying new plug today to make sure it’s not lean but definitely running better than stock. Running 40-1 and might buy a pro circuit shorty for a little more bottom end.
Yea going to be trial and error, tempted to buy the JD jetting kit if no luck but Yh also want to get a shorty as got stock exhaust
fredmotokx 10/25/2020 7:05am
10/25/2020 7:05am
As people stated above, there is a really good thread on how to jet our Mikuni TMX.
https://www.vitalmx.com/forums/Tech-Help-Race-Shop,42/KTM-HUS-125-150-2…

Below are some changes I did from stock on my 2021 150sx, the bike is way faster rolling out of the corner and has a bit more top end. No more oil dripping out of the exhaust.

10° to 20° sea ​​level
Needle pos 2 (from 3 stock)
Idle jet 32.5 (from 30 stock)
Main jet 490 (from 470 stock)
Airscrew 1.5 stock
Needle 42-71 stock
Needle Jet S4 stock
Slide #4 stock
Pump 91

Next season I will try a #5 slide with 42-74 needle as recommended in @AJ565 post. It should help clear even more the bottom end.

Hope this helps a bit, but I'm sure reading the whole thread I linked above will help you way more.



AJ565
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AJ565 10/25/2020 8:28am
10/25/2020 8:28am
mxfolife732 wrote:
Pretty sure 470 and 45 are the stock jets. 43-74 on 3rd clip is stock. I went about 2 screws out on the air screw. Trying...
Pretty sure 470 and 45 are the stock jets. 43-74 on 3rd clip is stock. I went about 2 screws out on the air screw. Trying new plug today to make sure it’s not lean but definitely running better than stock. Running 40-1 and might buy a pro circuit shorty for a little more bottom end.
mxallum77 wrote:
Yea going to be trial and error, tempted to buy the JD jetting kit if no luck but Yh also want to get a shorty as...
Yea going to be trial and error, tempted to buy the JD jetting kit if no luck but Yh also want to get a shorty as got stock exhaust
Don’t waste your time on the JD jet kit. Follow the jetting thread and live happily ever after.
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macz400
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macz400 10/25/2020 3:50pm
10/25/2020 3:50pm
You can play around with the Mikuni all day and it will be ok, only to then have to change it next time you go out. Or, bolt on a Keihin from the 2016 and live happily ever after.
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AJ565
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AJ565 10/25/2020 4:53pm
10/25/2020 4:53pm
macz400 wrote:
You can play around with the Mikuni all day and it will be ok, only to then have to change it next time you go out...
You can play around with the Mikuni all day and it will be ok, only to then have to change it next time you go out. Or, bolt on a Keihin from the 2016 and live happily ever after.
Gonna have to disagree with you on that one. The jetting stays the same all year in my bike unless it’s in the 30/40’s. Then it’s just a clip change maybe a pilot jet, just like you’d have to do with any carb.
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FGR01 10/25/2020 5:14pm
10/25/2020 5:14pm
macz400 wrote:
You can play around with the Mikuni all day and it will be ok, only to then have to change it next time you go out...
You can play around with the Mikuni all day and it will be ok, only to then have to change it next time you go out. Or, bolt on a Keihin from the 2016 and live happily ever after.
AJ565 wrote:
Gonna have to disagree with you on that one. The jetting stays the same all year in my bike unless it’s in the 30/40’s. Then it’s...
Gonna have to disagree with you on that one. The jetting stays the same all year in my bike unless it’s in the 30/40’s. Then it’s just a clip change maybe a pilot jet, just like you’d have to do with any carb.
Yeah, I would basically frame this another way. The Mikuni, once you are in the ballpark or very close with jetting, is fine over a broad range with minimal adjustment. Whereas the Keihin is more tolerant of less than perfect jetting and will remain "rideable" over a broad range in spite of it.
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15tc150
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15tc150 10/31/2020 7:33am
10/31/2020 7:33am
Check your reed block, the 2014+ ktm reed block is an absolute marvel of garbage, and can come from the factory with gaps between the reeds and sealing surfaces, you could spend your happily ever after chasing jetting and it’s the poorly designed reed block that’s messing you over. I bought one for my 2012 250sx to try out, same reed block design as the new bikes, just a different base plate everything mounts to, in 2 days, it went from good, to complete failure, and I could get a tan from how much light was poking through the amazing sized gaps at the reeds

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