2018 KTM 150sx spitting and sputtering

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6/9/2018 3:36 PM

I have a 2018 KTM 150sx that I just can seem to get running right. It spits and sputters at the low and mid range but is fine in the powerband. I have tried adjusting the air/fuel screw to lean it out and make it richer but it doesn’t seem to work. My fuel/oil ratio is 44:1 which has worked perfectly in all my previous bikes. Does anyone have any jetting settings that seem to work?

Please help

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6/9/2018 3:43 PM

Have you adjusted the pilot or clip position?

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vomiting equals disqualification.

6/9/2018 4:01 PM

Check the reeds. They are known to be bad from the factory. The mikuni carb is tempermental as well. Will probably take some time to dial in the jetting.

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6/9/2018 5:18 PM

BR8ES wrote:

Have you adjusted the pilot or clip position?

Not yet. I’m going to try moving the clip position up one notch to lean it out some when I get around to it.

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6/10/2018 8:13 AM

Check the reeds and get a JD jet kit.

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6/10/2018 8:48 AM

KTM317 wrote:

I have a 2018 KTM 150sx that I just can seem to get running right. It spits and sputters at the low and mid range but is fine in the powerband. I have tried adjusting the air/fuel screw to lean it out and make it richer but it doesn’t seem to work. My fuel/oil ratio is 44:1 which has worked perfectly in all my previous bikes. Does anyone have any jetting settings that seem to work?

Please help

Mine did the same exact thing a few weeks back. Thought I had everything jetted right and bike ran great until the first time I rode it in the super humid Texas weather and my bike did exactly what yours is doing. I played with air screw and clip neither did much. Ride a buddy's 150 the same day with a Keihin and his was perfect. I ordered a Keihin the next day lol. Runs great now.

FYI I am running 40:1 and my Mikuni setup was 470 main 32.5 pilot, 3rd clip.

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6/10/2018 1:10 PM

I have 2017 TC250, and 2018 TC125. Both bikes ran rich on bottom. After experimenting with air screw,pilot, and needle,,the solution for both was grinding the slide to equal a leaner 5.5-5.75. Stock on mine was 4.0 slides. The 125 was worst offender,,,it'd sputter hiccup blubber before cleaning out towards topend.. Now both are sharp and clean and responsive rolling on exiting tight corners. I run the recommended ratios and race gas in both. There's other threads on jetting the KTM brothers on here,,both KTM/Husky use same carb. Many are sourcing slides from other Jap models,,or having shops cut the stockers...with some finesse and a dremel it's a 10 minute do it yourself fix at home.

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6/10/2018 6:25 PM

rollin64caddy wrote:

Check the reeds. They are known to be bad from the factory. The mikuni carb is tempermental as well. Will probably take some time to dial in the jetting.

This^. Reeds on mine were like an open door. Like that from the dealer and would have made jetting a nightmare had I not swapped it out for a V Force.

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6/11/2018 6:32 AM

Both of my huskys had gaps in reed cages,,,I flat sanded and put new ones on the 250 as v force wheren't available yet,,and later v force on 125,,,,did they run better ..a little...solve jetting...no way. My old bikes with Boysen reeds always had gaps,,,after only 1-2 rides. Didn't make ther jetting this bad. Many many owners have found the slide is rich.... buy one or grind one or have someone grind yours. The lower 1/8-1/2 will wake up.

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6/11/2018 12:01 PM

And many mention no issues with the stock reeds, so go figure or no measurable difference with the VF4R...

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vomiting equals disqualification.

6/11/2018 12:02 PM

There is a good carb tuning thread over at KTM Talk about filing the carb slide, etc.

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vomiting equals disqualification.