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Bill_B

2019 KTM 125 SX jetting bike runs rough

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13 hours ago, 7Tktm said:

Hmm. We've mx raced 125s since 2008ish and up til Covid bought new bikes each year.  Last were 19s which we didn't even start until PWKs were fitted. 

But here you say you just ditch the mik before using it. Indicating to me, that you would rather spend 300 on a new carb instead of some jets.

I'm i missing something?

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No, you're not missing anything. We did have an ill judged experiment with a new 250 sx with a Mikuni as my son decided he fancied it. Won first time out on it (just a club meeting to be fair) then decided he didn't like it, so it was sold with 12 hours on it. However, it ran beautifully with the Mikuni, so nothing against these carbs. Just prefer PWKs. Don't think I've ever bought a new one though, we've built up loads of spares over the years - will be some garage sale when he stops racing lol. Bob

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Well, that's sort of my point, you shouldn't have to buy new seals and slides for a new bike, KTM should have it fixed first time out and not leave their customers to spend money to work it out. That's all. Now I'd better not say too much about our cone valves and trax or I'll be told that the standard suspension is great for 125 racing.......lol Bob

Edited by 7Tktm

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I agree and for the price of what a new bike is now days one should not have to touch anything I redid my old 99 and thrilled I know it it's paid for I'd rather put a 3rd if only a quarter of the money into it to make it absolutely new again burst as the price of a new bike which is above 8 grand Personally I feel that the bikes are so good and have been for the last 15 years that anything within last 10 years could totally be redone and totally competitive the motors definitely got enough it's all in the suspension and set up

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You should not have to buy a slide ,but you don't have to lol 

You see the afr ,it's really good ,if you ride at low throttle and at altitude you might need a slide 

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10 minutes ago, mog said:

You should not have to buy a slide ,but you don't have to lol 

You see the afr ,it's really good ,if you ride at low throttle and at altitude you might need a slide 

Mog I have to disagree with you here.  If you ride at low throttle and sea level you’ll be fouling plugs (with the factory included jets and/or the KTM recommended settings) and have spooge dripping on the swing arm. Now keep in mind I’m talking about a 2021 125xc, not a 150 and not an older 125.   I promise I’ll update on the results of the #5 slide-hopefully this weekend!

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Back when I bought my 99 200 the hot set up was to go to a 7 slide and and NOZH needle that cleaned it up considerably that was in 99!! I totally can understand needing to do some jetting on a new bike in but having to buy a bunch of parts for the carburetor the gasket and all that other nonsense that isn't right and KT m's very aware of it Don't get me wrong I love the Orange bikes I've ridden KTM since back in the day when they were called pentons really showing my age now

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Marcus, I maybe shouldn't have commented as I now realise the post isn't about flat out mx racing/practice so I'll bow out gracefully! Bob

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3 hours ago, Pipski65 said:

Mog I have to disagree with you here.  If you ride at low throttle and sea level you’ll be fouling plugs (with the factory included jets and/or the KTM recommended settings) and have spooge dripping on the swing arm. Now keep in mind I’m talking about a 2021 125xc, not a 150 and not an older 125.   I promise I’ll update on the results of the #5 slide-hopefully this weekend!

Depends on the oil as well 

I rode a 17 TC 125 and it wasn't as bad as people are saying the 21 is lol ,that was the worst year for jetting 

If you do ride a lot on part throttle a slide will work ,bit also often the leaner clip works just like it always has 

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On 2/22/2021 at 4:49 PM, SmokinJoe said:

There's a post on vital mx from like December. With a guy with a totally stock 2019 150sx. Who started a post because his bike had the bog miss around 3/8 throttle. He had done the jd jetting block swap and it didn't resolve the issue.

An owner of an 2018 who took the time to properly dail in the mikuni. Strongly recommend going to the #5 slide and 3 sizes leaner on the needle. In that post was a link to a thread from 2018. Where he and a few other owners. Hash out took the time to come up with the jetting that fixed the lean pilot to the too rich slide/needle. That gets rid of the bog miss around 3/8 throttle. 

Not only does it fix that the bike runs better through the entire rev range and makes better power and is not as effected by different temperatures as much. 

Other owners with orange n white 125's n 150's from 17 thru 20's. Who did the swap to the recommend jetting also reported the same positive changes. 

Similar changes to the mikuni on the 17+ 250/300's also have the same benefit. 

So you trying to tell me that running a hotter plug to solve jetting is like trying to fix it by changing premix ratios.

Those settings in that Vital thread from 2018, are setting that I came up with, for both the 125/150 and the 250/300. I have a bunch of time in testing on both of those platforms. The specs have been refined a little bit over time for different types of fuel, but for the most part are still the same for pump fuel. AJ updates that thread every once and a while. I post on TT often.

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Link to thread?

Curious to see if it ended at 

 Sea level to 1500'

#5 slide

Damn near any needle, Suzuki preferred 

27.5 ~30 Pilot , 

 480-500 main,  bigger the better with no ill effects usually 

Edited by Turn,TheScrew

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