KTM 250 SX Carb Swap

MxKing809
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MxKing809
Edited Date/Time 11/29/2017 2:56pm
Ok fellas,

Is the 38mm carb worthh it on a 250 sx or is it only needed on the 300 sx?

I'm looking at them online and was curious if I could just get the pwk air striker carb with the screw top, or if I had to find one with the top plate like the stock 36mm?


Looking at this one.....
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Digger29
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Digger29 2/27/2014 5:08am
2/27/2014 5:08am Edited Date/Time 2/27/2014 5:15am
Yes it's a great mod and definitely worth doing. Just put the 38 PWK from a 13 125/150SX on your bike. It is the exact same size body as the 36 you'll be swapping it with.
MxKing809
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MxKing809 2/27/2014 5:14am
2/27/2014 5:14am
Ok thanks Digger!

It'll help on the stock top end right? I don't need the 300 kit to notice a gain?
nytsmaC
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nytsmaC 2/27/2014 5:16am
2/27/2014 5:16am Edited Date/Time 2/27/2014 5:17am
The screw top like your picture is longer than stock.
hellion
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hellion 2/27/2014 5:48am
2/27/2014 5:48am
I like the screw top carb better mainly because it's so much easier to work on. I also find it fits no problem.

The Shop

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KTMShane699
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KTMShane699 2/28/2014 5:30am
2/28/2014 5:30am
My 2014 250 SX has the carb off of a 2014 125 SX on it. Used a 40 pilot, Suzuki NECJ needle, 175 main and the. 6.5 slide out of the 250. Digger gave me the hot setup.

Also means I have a brand new 36 carb if anyone needs one...

Shane
GimpIndustries 2/28/2014 8:20am
2/28/2014 8:20am
Digger29 wrote:
Yes it's a great mod and definitely worth doing. Just put the 38 PWK from a 13 125/150SX on your bike. It is the exact same...
Yes it's a great mod and definitely worth doing. Just put the 38 PWK from a 13 125/150SX on your bike. It is the exact same size body as the 36 you'll be swapping it with.
The 125 and 150 have different part numbers for there carbs. Which one of these is the correct one?

2013 125SX - 50331101544 - CARBUR. KEIHIN PWK 38S AG
2013 150SX - 51531001444 - CARB. KEIH. PWK 38S AG BC0
Digger29
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Digger29 2/28/2014 2:11pm
2/28/2014 2:11pm
I have the 38mm carb from the 2013 125SX. That's definitely a head scratcher to me because I've worked on & jetted a number of KTM 125SX & 150SX's in the last cpl of yrs & I didn't see any differences on the either 38s that come on the 125SX or the 150SX. Remember if you do it to swap out the 7.0 slide that comes in the 125s 38mm carb for the 6.5 that is in your 36 on your 250SX.
slipdog
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slipdog 2/28/2014 2:34pm
2/28/2014 2:34pm
It's not uncommon for a manufacturer to have different #'s for the same part to track what model parts are being sold for.

For instance, Honda uses different letter combinations in their part #'s to designate models like KRN or MEN. Even though the 2007 CRF 450, 250 and CR 250 use the exact same fork seals and bushings, they will have different #'s depending on what microfiche you look at.
neverwasfastenuf 2/28/2014 5:55pm
2/28/2014 5:55pm
slipdog wrote:
It's not uncommon for a manufacturer to have different #'s for the same part to track what model parts are being sold for. For instance, Honda...
It's not uncommon for a manufacturer to have different #'s for the same part to track what model parts are being sold for.

For instance, Honda uses different letter combinations in their part #'s to designate models like KRN or MEN. Even though the 2007 CRF 450, 250 and CR 250 use the exact same fork seals and bushings, they will have different #'s depending on what microfiche you look at.
Those dirty little secrets, albeit smart. Thanks for the clarification.

Big brother will have all our moves mapped out for us before we even make a decision.

Wink
KTMShane699
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KTMShane699 3/1/2014 4:34am
3/1/2014 4:34am
Digger29 wrote:
Yes it's a great mod and definitely worth doing. Just put the 38 PWK from a 13 125/150SX on your bike. It is the exact same...
Yes it's a great mod and definitely worth doing. Just put the 38 PWK from a 13 125/150SX on your bike. It is the exact same size body as the 36 you'll be swapping it with.
GimpIndustries wrote:
The 125 and 150 have different part numbers for there carbs. Which one of these is the correct one? 2013 125SX - 50331101544 - CARBUR. KEIHIN...
The 125 and 150 have different part numbers for there carbs. Which one of these is the correct one?

2013 125SX - 50331101544 - CARBUR. KEIHIN PWK 38S AG
2013 150SX - 51531001444 - CARB. KEIH. PWK 38S AG BC0
The different part numbers could also represent a difference in jetting from the factory. I don't know if the 125/150 share completely identical jetting off the top of my head. But something as simple as a needle or jet change would require an entirely new part number from the OEM.

Shane
Kenman
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Kenman 3/1/2014 5:35pm
3/1/2014 5:35pm
Would this be the same swap and jetting for a 2013 250sx? At sea level?
MxKing809
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MxKing809 3/1/2014 6:59pm
3/1/2014 6:59pm
Yup, they're identical for the most part. Head shape is different and reed cage is a different brand, but it'll work just fine on a 13
dk0r
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dk0r 5/21/2014 5:52pm
5/21/2014 5:52pm Edited Date/Time 5/21/2014 5:58pm
I'm looking to do the carb swap on my 2012 250sx and so I ordered the 2014 125sx carburetor (KEIHIN PWK 38S AG | 09 [SKU#: 50331101544]) shown here:
http://www.motosport.com/dirtbike/oem-parts/KTM/2014/125SX/CARBURETOR?f…

What I received is pictured below. Note that this is not a screw top like MxKing809 showed in his first post:


Now, I've realized that Digger29 specifically recommended the 2013 125sx carb.
However, there seems to be no difference between the 2014 that I ordered (in the link above) and the 2013 in the link below:
http://www.motosport.com/dirtbike/oem-parts/KTM/2013/125SX/CARBURETOR?f…

--Do all 2013/14 125sx's come with screw tops?
--Was the screw top phased out in 2014?
--Have I received the wrong part?
Digger29
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Digger29 5/21/2014 6:59pm
5/21/2014 6:59pm
That's definitely the right carb. Keep the 6.5 slide from your stock 36 and install that in the 38 carb. Also don't forget to get the Suzuki NECJ needle and put a 175 main jet in it and you'll be good to go.
stonerb
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stonerb 5/21/2014 7:28pm
5/21/2014 7:28pm
Digger,

What are the benefits of running the 38mm rather then the stock 36mm?
Digger29
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Digger29 5/21/2014 7:42pm
5/21/2014 7:42pm
Better top end without sacrificing that much bottom end at all. I really didn't notice any loss in bottom end. If you put the 38mm carb and a Vforce4 and run the jetting that we're running you're bike will be a whole different bike. I rode a buddy's 14 Husky TC250 on Monday at MX207 in ME that we did the above mods to and the bike flat out hauled ass! He was thinking of selling it until we did the mods to it and now he loves it. It was GOOD!!
dk0r
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dk0r 5/21/2014 7:54pm
5/21/2014 7:54pm
Digger29 wrote:
That's definitely the right carb. Keep the 6.5 slide from your stock 36 and install that in the 38 carb. Also don't forget to get the...
That's definitely the right carb. Keep the 6.5 slide from your stock 36 and install that in the 38 carb. Also don't forget to get the Suzuki NECJ needle and put a 175 main jet in it and you'll be good to go.
Thanks for clarifying.
I was under the (wrong) impression that the screw-top was the stock carb on 13/15 125/150sx --it is not.

I'll post again after testing it tomorrow.

Pit Row

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seth505
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seth505 5/22/2014 1:55pm
5/22/2014 1:55pm
I have a question, if people are going to the 38mm carb then why not just go to a smartcarb or Lectron?

I have similar jetting to above (with my stock carb) and I feel like my bike runs sweet.
Digger29
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Digger29 5/22/2014 2:28pm
5/22/2014 2:28pm
Have you read the review's from the all of the guys who running the Smart Carb? I think I've read over 200+ pages and I don't think there is one guy that has his cast or billet Smart Carb working correctly. It appears to be a very flawed product. I'm all set with that. I'll stick with my perfectly jetting and starts on the first kick every time 38mm Keihin carb.
seth505
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seth505 5/22/2014 2:52pm
5/22/2014 2:52pm
Digger29 wrote:
Have you read the review's from the all of the guys who running the Smart Carb? I think I've read over 200+ pages and I don't...
Have you read the review's from the all of the guys who running the Smart Carb? I think I've read over 200+ pages and I don't think there is one guy that has his cast or billet Smart Carb working correctly. It appears to be a very flawed product. I'm all set with that. I'll stick with my perfectly jetting and starts on the first kick every time 38mm Keihin carb.
Wow, that's a good reason then! Haha, I haven't been keeping up on that research, they just sounded like a cool idea in theory when they were first brought up. Definitely happy with my conventional carb, idea of even more top end with the 38mm sounds awesome though...
Crush
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Crush 5/22/2014 6:45pm
5/22/2014 6:45pm
The factory 2 smoke guys down here run the carb off the 04 model...
Steveo_supremo 5/23/2014 7:44am
5/23/2014 7:44am
Digger29 wrote:
Have you read the review's from the all of the guys who running the Smart Carb? I think I've read over 200+ pages and I don't...
Have you read the review's from the all of the guys who running the Smart Carb? I think I've read over 200+ pages and I don't think there is one guy that has his cast or billet Smart Carb working correctly. It appears to be a very flawed product. I'm all set with that. I'll stick with my perfectly jetting and starts on the first kick every time 38mm Keihin carb.
I think that's mostly because the guys who are happy with them aren't posting much. I'm very happy with my 38mm cast Smartcarb on my '13 250SX. I have about 15 hours on it now (95% MX use, 5% singletrack). More/smoother low end, WAY MORE top end and over-rev, plus I can adjust the jetting in a matter of seconds with my thumb and forefinger.
Hal_396
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Hal_396 5/23/2014 10:29am
5/23/2014 10:29am
So what slot are you putting the clip in on the Suzuki Needle?
Digger29
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Digger29 5/23/2014 1:23pm
5/23/2014 1:23pm
Hal_396 wrote:
So what slot are you putting the clip in on the Suzuki Needle?
The 3rd setting on the needle.
Hal_396
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Hal_396 6/3/2014 3:47am
6/3/2014 3:47am Edited Date/Time 6/3/2014 5:14am
I ordered one yesterday. There on sale for $310.00 Can't wait until it arrives..........
Digger29
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Digger29 6/3/2014 5:19am
6/3/2014 5:19am
You're going to be thrilled with the bump in performance. It will feel like a whole different bike. It's well worth it and I was able to sell my stock 36 carb on eBay for over $200 so making the switch to the 38mm carb cost me somewhere around $35. Do yourself a favor and borrow a Vforce 4 to try out as well. After riding 2 14s (and this is purely my opinion) the VForce is the way to go on the 14-15 KTM 250SX or the 14-15 Husky TC 250.
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seth505 6/3/2014 7:51am
6/3/2014 7:51am
Hal_396 wrote:
I ordered one yesterday. There on sale for $310.00 Can't wait until it arrives..........
Where did you order from?
Hal_396
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Hal_396 6/3/2014 10:05am
6/3/2014 10:05am Edited Date/Time 6/3/2014 10:08am
2013 125 SX Carb


I'll see about the VForce next. Did you try it with the stock Posion Rad valve?
seth505
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seth505 6/3/2014 10:22am
6/3/2014 10:22am
Hal_396 wrote:
2013 125 SX Carb


I'll see about the VForce next. Did you try it with the stock Posion Rad valve?
Thanks, haha I feel stupid...I actually checked motosport but just looked under 2014 and it said 'not available' for the carb. Didn't even think to check the previous year.

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